Got questions about growing vegetables and fruit in Maine?

Extension experts identifies a plant sample for a client; photo by Edwin Remsberg

Ask the UMaine Extension gardening experts!

With years of experience in home horticulture and commercial agriculture, our experts help beginning gardeners achieve successful harvests, encourage gardeners and commercial farmers to donate excess produce to those in need, and use gardening as a vehicle to develop communities.

If you have a question about growing vegetables and fruit in Maine, you are welcome to

Q&A 2017

Answers to this season’s gardening questions are provided by Donna Coffin, Extension Educator, UMaine Extension Piscataquis & Penobscot Counties; Caragh Fitzgerald, Associate Extension Professor, Agriculture, UMaine Extension Kennebec County; Kate Garland, Horticultural Professional, UMaine Extension Penobscot County; Marjorie Peronto, Extension Educator, UMaine Extension Hancock & Washington Counties; and Frank Wertheim, Extension Educator, Agriculture/Horticulture,UMaine Extension York County.

Asiatic bittersweet berriesQ: What is the best way to get rid of bittersweet?

A: Small patches can be hand-pulled. Take care to remove the entire root to prevent resprouting. Low patches have been successfully removed by cutting the vine and treating the regrowth with a triclopyr herbicide. Control is more successful in taller patches when cut stems are immediately painted with triclopyr or glyphosate. This plant has a substantial seedbank, and complete eradication may depend on repeating control methods for several years. For more information please read, Asiatic Bittersweet.

Rhododendrons in bloomQ: We have dug up some of the plants that rooted around the rhododendron. How deep should we plant the piece that was underground? It was rather shallow.

A: I assume you are talking about new shoots from the mother rhododendron plant? If so, you can dig them and place them where you would like to have the new plant. Plant it at the same depth it is now.

Q: I have some young cherry trees, I planted them bare root about 10 years ago. Some of them are developing a wilted and dying tendency on some of the branches. Is there anything I can do? Not all branches are affected at this point.

A: It is hard to say without getting a specimen to our Pest Management Office for diagnosis. However, here is a link to a fact sheet on cherry diseases.

Q: I planted my veggie garden and it is now infested with what appears to be teeny tiny mites of some sort they are climbing all over the sides of the raised beds they’re all through the dirt they’re everywhere would like to know what they are and how to get rid of them.

A: We will need either some very good digital images or a sample of these mites or insects to make an ID and any recommendations. Please follow the instructions here for the Insect and Plant Disease Diagnostic Lab, Submitting Insect Specimens.

Q: I have a tree that I believe was recently struck by lightening. It seems to be intact but has a long vertical break in the bark where the lightening apparently traveled. Much of the bark has been darkened. My concern is whether the tree is now in a weakened condition and possibly a threat to toppling over and causing possible property damage. Can you provide information about this or recommend a referral for assistance?

A: It’s difficult to say what the long-term effects might be from this lightning strike. Some trees go on to live long lives following a strike and others eventually succumb to this injury. Your tree is not in imminent danger of falling over, so I suggest a “wait and see” approach. If you notice symptoms like those described in this University of Florida publication, Lightning damages trees.  You should take steps to remove the tree. You can find licensed arborists at the Maine Department if Agriculture, Conservation and Forestry website.

ripe peaches on treeQ: What source do you recommend for bird netting for fruit trees? I read that 1/4″ to 1/2″ openings are best. But I am only finding 5/8 to 3/4″. We have a cherry and a peach tree, as well as blueberries and concord grapes.

A: I cannot recommend a specific vendor, but yes, the smaller the openings, the more successful you will be at preventing birds from taking your fruit. Since you have multiple plants to cover, it might be worth searching online as well as at local garden centers. A quick search yielded many results for me.

Q: We have a well that is about 350 feet deep. Most of our property is either exposed ledge or ledge just below the surface. We have some fields surrounded by ferns and wild blueberries. The fields were originally planted with grasses for cows and then horses. I mow them regularly but lately there is an abundance of nasty weeds that detract from the visual appearance of just grass. What kind of weed killer and what kind of fertilizer could I use on the fields? In the past, I’ve used the type of weed killer that is absorbed into the plant through its leaves and supposedly then kills the root, leaving no poison and harmful residue in the soil. That though is one weed at a time and is VERY time consuming. 

A: I do not recommend herbicides for homeowners. You mentioned you are on ledge, have a well nearby, and that this field is currently only for ornamental purposes. Herbicides should be reserved for instances where there is a health or safety risk, economic benefit, and used only after all other options have been exhausted. Something you might consider instead is converting this area to pollinator habitat. As you likely know, bee habitat is on the decline as are bee populations. How to Create a Bee-­Friendly Landscape is a great guide for how to get started. If you decide to go in this direction, you will also have the added benefit of less mowing! Using less fuel in your mower creates fewer emissions, costs you less, and gives you more time to enjoy our beautiful Maine summers. To maintain the open space, mowing or bush hogging once a season will keep tree saplings from getting established.

Plant or weed
Plant or weed?

Q: I have a plant that has come up in my flower garden this year and I am not sure if it is a weed. Please see photo.

A: I believe this plant is Narrow Leaf Plantain: Plantago lanceolata. This is a weed and has invasive tendencies. I would remove it and not let it go to seed. Here is a link to more photos and information.

Q: Our Plum tree has a growth on it. I’m afraid that it will spread to the green gage plum tree about 40 feet away or the apricot tree about 50 feet away. There are plums, pears, and apple trees even further away but in the same small orchard of about 20 trees. A walnut and hazel nut tree are within 40 feet. First question, how do I get rid of the infected plum tree without spreading the infection (or whatever it is)? I’m afraid when we cut it down it will spread spores, but leaving it isn’t good either. No other tree appears infected. Second question, what can we do to help the nut trees produce?

tree fungus
Black Knot of Plum and Cherry.

A: The growth you see on your plum trees is Black Knot of Plum and Cherry. I have listed some links to fact sheets on the disease, which include control strategies and pruning out and removing infected branches. It will spread to other plum or cherry trees but will not spread to nut trees. As far as helping your nut trees produce, I would follow general soil test results. Nut trees do take years to start producing.

Q: I have three high bush blueberry bushes that were pruned in March, I still have dead branches that need to be lopped off. Can I prune these branches now or mark them and cut them next spring?

A: Dead and broken branches can be removed (pruned out) at any time. The dead branches you see now most likely were winter killed and hard to spot when you pruned in March.

For more information on general care of highbush blueberries and pruning information please read this bulletin, Growing Highbush Blueberries.

Raised bed gardens
Photo by Tracey O’Connell

Q: I have a 24′ by 100′ raised bed vegetable garden. Is there any flower I can plant around the perimeter to keep pests (animal or insect) away?
A: There is no one flower that will deter both insects and animal pests. The best known deterrent plant is marigolds, which is unfortunately a bit of a myth. They do deter, and can be harmful to some soil-borne species of nematode plant pests, but there is no research to show they can deter other insects. In fact, marigolds may even attracts spider mites and snails.

Having said that, here are links to articles on companion planting from Illinois, Penn State, and Rutgers Cooperative Extension, which should help you decide what might be best for your garden bed area:

Q: Can you tell me why so many of the maple trees have batches of seeds on them this year? I have noticed that some have just seeds and no leaves but most have both. The two in my front yard are about 10 years old and this is the first year that they have batches of seeds along with leaves.
A: The red maple trees seed in the spring, while sugar maples seed in the fall. This does seem to be a heavy seed year for Red Maples so I think that is what you are seeing.

lilac with stressed flowers and leavesQ: We have several older lilac trees that are experiencing leaf curl and appear to have been chewed by some pest, although none are visible. The flowers have died halfway through their bloom. I did not prune much last year and was preparing to prune heavily this year but not sure the best way to help them recover. Is this blight?

A: Without physically looking at the plant, it is hard to make a diagnosis. That being said, you can send samples of leaves, flowers and other parts of the plant that are displaying symptoms, to our Insect and Plant Disease Diagnostic Lab – How to send a plant sample Pest Management lab in Orono. Our pathologist will take a look at the samples and contact you with his findings. There is no charge for this service.

You might also find this informational fact sheet from Penn State about common lilac diseases useful.

Lilacs are also susceptible to two insect pests lilac borer and oystershell scale.

Once lilacs are well established, pruning immediately after bloom can improve their vigor, appearance and future flowering. The goal of pruning is to maintain a clump of 7 to 10 stems of different ages. Cut a third of the oldest wood to the ground no more often than every 3 years. The oldest wood of lilacs is more susceptible to infestations of borers and scale insects. Also, thinning out vigorous top growth will increase flower bud formation by allowing sunlight to reach the center of the plant.

Q: Looking for someone to rototill an additional garden space at my home.

A: I would suggest checking your local yellow pages for gardening/landscaping companies.  If they are not able to do it, they may know of someone who does.
You may also wish to check out the Maine Landscape and Nursery Association list of landscape professionals.

Stewartia tree without many leaves
Stewartia tree without many leaves.

Q: Our stewartia tree in not leafing out this spring. Due to its location it may have been subjected to a lot of salt this winter. Do you have any suggestions for reviving this tree before we call an arborist? Mulch was applied within the past month.

A: Fortunately, Stewartia pseudocamellia (Japanese Stewartia) has no significant insect or disease problems. That being said, Stewartia is fussy about culture requirements. It is hardy to Zone 5 and performs best in part sun, preferably morning sun with shade from the hot afternoon sun, and evenly moist, well-drained acidic (pH 4.5 – 6.5) soil that has good organic matter content. Some leaf burn might be evident in drier summers (like we had last year) if the tree is in full sun.

Salt used for melting ice on pavements in during the winter can be quite harmful to trees. Salt damage occurs on plants when salt is deposited by spray from passing cars on stems and buds of deciduous woody plants. Salt spray can cause salt burn on buds, leaves and small twigs. Salt spray can also cause damage by desiccating the bud scales, exposing tender tissues of the developing leaves and flowers. The unprotected developing leaves and flower buds dry out and are often killed by the cold winter wind. Many times, the damage is not evident until late winter or spring. Needle or leaf browning, bud death, and branch dieback on the side of the plant facing the road or sidewalk is a common sign of salt spray damage. Damage to deciduous plants is not seen until growth resumes in the spring.

Plants are also affected by dissolved salts in runoff water. The dissolved sodium and chloride ions can displace other mineral nutrients in the soil. Plants then absorb the chlorine and sodium instead of needed plant nutrients which can lead to leaf burn and die-back.

Rock salt also causes damage when salt laden snow is plowed or shoveled onto lawns and garden beds. Salts in the soil can absorb water. This results in less water being available for uptake by the plants, increasing water stress and root dehydration.

Most of Maine had a lot of snow this winter and coupled with the drought we had last summer, your tree might be showing signs of stress from the two events. It wouldn’t hurt to have an arborist come over to check it out to see if the tree is still alive, or you could wait it out and see how the tree performs over the next few months into next spring.

Adult & nymph deer ticks
Adult and nymph deer ticks. Image by Griffin Dill.

Q: I live on the coast of Maine. At least two of our neighbors use “Talstar” insecticide outside to control, what they tell me are ONLY ticks and mosquitoes. I am researching the chemical and see that it is especially toxic to bees, among 75 different insect species, as well as aquatic life. Would you happen to have any more information? Are there restrictions by town? Do you know what towns prohibit this?

A: Pesticides can provide substantial benefits in, for example, maintaining public health and in managing pests in food production. However, as you are aware, they are a powerful tool that, if applied or handled incorrectly, can have unintended and sometimes harmful consequences.

Bifenthrin is the primary active ingredient in Talstar. This factsheet, National Pesticide Information Center highlights some of environmental concerns you already stated. It is important to note that these concerns can come about only when the pesticide is applied incorrectly. Each pesticide undergoes rigorous testing by the Environmental Protection Agency (EPA) before it is available to the general public. The information that comes out of that testing is contained in the label attached to each pesticide bottle sold. The label goes into detail about how to apply the pesticide correctly (rate of application, timing, weather conditions to avoid, set backs from sensitive environmental locations, safe storage conditions, and more) — so that those environmental concerns don’t happen.

Talstar is registered for sale in Maine. I am not aware of restrictions of its application by town. Pesticides need to be treated with great respect, but if handled, applied and stored properly can provide the intended benefit with minimal cost.

I commend you for seeking out more information! A suggested next step is to get the entire name of the product (there are 18 different registered formulations of Talstar in Maine alone!) — and look up the exact label for that product. It may help you to read the label in its entirety — to be fully aware of the potential environmental impact and to see the actions suggested, via the label instructions, to mitigate those potential risks.

broccoli in the gardenQ: We’ve had bad luck growing broccoli. Most years it bolts so if there are heads, they are very small. I feel we get the plants in the ground early enough and a lot of time we buy them already started. Could a certain nutrient be missing from our soil that could cause this to happen? Also, radishes don’t bulb up well even when thinned. Ears of corn are small. Legumes do well, as do peppers and tomatoes.

A: Sorry to hear you have struggled growing (or not growing) various vegetables in your garden. I would first make sure you are using Vegetable Varieties for Maine Gardens that are recommended for our Maine climate. Using varieties not adapted to our climate can lead to bolting (tied to day length and heat) and unproductive plants.

How to Prevent Cool Season Crops from Bolting has a good description on why plants bolt and how to manage it. It is important to note that the longer days of summer triggers bolting. You may have better success by planting broccoli towards early July for a Fall harvest (the days are getting shorter).

Growing broccoli, cabbage and cauliflower in Minnesota has a good overview on growing broccoli and other cole crops.

You may also wish to test your soil and make sure that the plants have the nutrients they need and correct pH to grow well.

Keep an eye out for pests and diseases. If you see anything that looks suspicious, bring it to your local Extension office for identification. The sooner you identify and address any pest problems, the easier they are to manage.

Gardens need full, direct sun as well, so make sure they are sited in a good location.

Q: Can I plant corn with Lumite Ground Cover? Would I burn a long continuous hole in the fabric for the seeds?

A: Lumite is okay to plant with edible crops. For corn placement, you can burn individual holes with a blow torch. The torch will cut and melt the edges so the weave doesn’t come unwoven. This is okay but creates holes in your fabric, and doesn’t allow you to easily adjust for crops with different spacing without making more holes (and more spaces for weeds to pop up through).

Alternatively, you can use the 3-foot-wide rolls of Lumite, leaving a gap in between when you place the rolls down. You plant the corn in that gap space; i.e., you place a 3-foot strip on the outside, then a row of corn, then another 3-foot-wide strip in the middle, then another row of corn, etc.

Q: We have tried to grow bell peppers in zone 4 with no success. Any suggestions would be greatly appreciated.

A: Sorry to hear you have struggled growing (or not growing) bell peppers in zone 4. For Maine’s climate please read, Vegetable Varieties for Maine Gardens.

In Evaluations of Sweet Pepper Varieties you will find trial results for different sweet peppers grown in Maine.

Here’s a good overview on how to grow strong pepper seedlings for transplant.

Also be sure to test your soil to ensure that the plants have the nutrients they need and correct pH to grow well.

Keep an eye out for pests and diseases. If you see anything that looks suspicious, bring it to your local Extension office. The sooner you identify and address any pest problems, the easier they are to manage.

Peppers need full, direct sun as well, so make sure they are sited in a good location.

Q: Do you have a frost date map for Washington County?

A: Freeze/Frost Occurrence Data (PDF) can help you determine frost-free dates for locations throughout Maine. You can also look up your first and last freeze/frost dates by zip code. Our Plant Hardiness Zone Map of Maine includes additional information.

Q: I have a number of morella pensylvanica northern bayberry shrubs in my yard. How would I go about propagating them from woody stem cuttings?

A: The best way to propagate would be from softwood cuttings. For more information on propagating from both softwood and hardwood cuttings, see Propagation of Woody Ornamentals by Cuttings (PDF) and Propagation of Shrubs from Softwood Cutting. Also note that barberry is suckering in its habit. Shoots with roots can be separated from around the bases of the parent plants and planted elsewhere.

Highbush blueberry branches
The green shoots are last summer’s growth. The gray branches are older growth that are part of the cane. The longer, thicker shoots on the left of the photo (8-10”) should be saved. The weaker shorter shoots on the right should be trimmed off.

Q: Some of my high bush blueberry bushes are just dead wood. They were fine last fall. What might be the problem? They were not fertilized after July.

A: We had a hard winter and it sounds as though your blueberry bushes have winter dieback. Highbush blueberries push the edge of their adaptability to Northern New England temperatures and so it is not uncommon for them to get injured and die back during a harsh winter. As a quick aside, I have had to prune some of my established ornamental shrubs back hard this spring because they had a lot of dieback this winter. Thankfully, the heart of the shrubs, closer to the ground and buried under some leaves, survived! Highbush blueberries are not related to my shrubs, I added that in just because it was an indicator to me on how hard this winter was on some of our plants.

See Growing Highbush Blueberries for information about pruning out the damaged wood. Hopefully, part of your plant survived and will regrow. Depending on how much damage there was and how old the blueberry bushes are, it may take a few years before the blueberry is back to its size last fall.

Going forward, you may want to see how you can protect your blueberries during the winter. For example, consider relocating to a more protected site.

late blight on tomatoes
Tomato plants infected with late blight.

Q: What can I plant in my raised beds that had tomatoes that suffered blight last year? I removed and disposed of the plants the best I could. I was considering peas and/or beets, but would greatly appreciate suggestions.

A: Your question is a bit difficult to answer in that I am not exactly sure what you mean by blight — early blight, late blight, septoria leaf spot? “Blight” is often used to describe several different, completely unrelated, plant diseases.

I will take a guess that perhaps you were struggling with early blight. UMaine Extension’s bulletin #5087 Early Blight of Tomato and University of Minnesota’s Early blight of tomato include pictures of what the disease looks like and how to manage it.

In short, anything NOT in the solanaceae family can be planted in those raised beds. The solanaceae family includes potatoes, tomatoes, peppers, and eggplants — so avoid these in the raised bed and all other crops are fair game. Vegetable Varieties for Maine Gardeners includes a list of crop varieties suited to Maine.

Keep in mind that early blight is a fungus and can overwinter in the soil and crop residue. I would encourage you to plant early blight resistant solanaceous crops in the rest of your garden area to avoid/minimize damage by any early blight spores that have carried over the winter.

The publications cited above have additional management techniques.

If, after looking at the pictures, you determine that your tomatoes did not have early blight last year, please drop us another line — along with photos, if you have them — so that we can identify the disease you struggled with. Proper identification will help us give you the best information on how to control the disease going forward.

Q: How far away from the leach field should vegetables be planted? Would a raised bed within ten feet be safe?

A: Ten feet may not be a safe distance from the absolute edge of your leach field, especially if it’s an older system or you don’t know where the exact boundaries are. For more information, see our fact sheet Vegetable Gardens & Septic Systems Don’t Mix.

Comparison of 2 common types of white grubs in Maine: European Chafer grub (on left) is larger than the Japanese Beetle grub (on right). Photo by G. M. Dill.Q: My yard is plagued with grubs (2nd year in a row). We have treated with grubex (multiple times before forecasted rain) but nothing is working. Large sections of our yard have dead grass and the skunks are having a feast every night eating the grubs. Are there any other options to get rid of grubs in our yard?

A: I would encourage you to give GrubEx, or another pesticide, another try. The way to control grub damage is to kill the larvae (although I know it’s hard to wait to do that as the adult grubs/skunks are tearing up your lawn right now).

GrubEx is an effective product, but it controls the eggs and must be applied 60-90 days before the eggs are laid in July. This means that application(s) should occur in April (so ASAP). The product label (GrubExSeasonLongGrubKiller (PDF)) said it provides 4 months of control. So, if you apply in April, give it 60-90 days to take hold (June to July) — you’ll be covered for this summer (June – September).

Making sure the product is applied 60-90 days before the eggs are laid is important because it takes time for GrubEx to work itself into the roots of the turf so that when the larvae feed on the roots they consume the GrubEx as well and die.

Please read this publication carefully: Grubs Got Your Lawn? (PDF). It is chock full of great information — i.e. how the pesticides work, egg laying dates, the alternative use of water to control grubs, how to repair lawns with grub damage, etc. NOTE: Please use the water method or the pesticide. Do not apply the pesticide and then water consistently — you will wash away the pesticide.

Goutweed (Aegopodium podagraria); photo by Leslie J. Mehrhoff, University of Connecticut,

Q: My raised beds a full of Bishop’s Pie Weed. How do I get rid of it? The plants break apart when I try to dig them out. The bits stay in the soil and seem to regenerate!

A: Bishops Weed, Goutweed, or Aegopodium podograria, is one of the most aggressive plants in the garden. (The variegated one is called Snow-on-the Mountain.) Most people have a very hard time getting rid of it because it’s in and around the stems and roots of other desired plants. It’s one of the plants that can hitch-hike on home-dug specimens, unfortunately making gardeners cautious of plant sales.

Goutweed is on the invasive plant list in many states. It is finally listed in Maine. Here’s the fact sheet about goutweed we often send to clients. It lists different mechanical and physical control methods, which should always be tried before chemical controls.

When using chemical controls, always follow label instructions.

Translocated herbicides are not effective in the spring, when energy is flowing UP from the roots to the leaves. They work only when the plant is photosynthesizing completely (after June 10 and into early fall) and all energy is going DOWN from the leaves to the roots, translocating the poison with it. If you tire the plants out first (cut, pull, weed whack), the herbicide will be even more effective. The same applies to poison ivy and other plants with perennial roots.

Covering the whole area with black plastic can further weaken the colony. (This can only be done in a large clear area of course.) After the plastic comes off in late August, weed whack, allow it to re-sprout, and then hit it with an herbicide once it’s an inch tall.

Be very careful when digging or sifting the roots. The goutweed can then colonize a compost pile or other are where the material is discarded.

garlicQ: I did not harvest my garlic last fall. The bulbs are all sprouting now. Can I successfully break them apart and replant at this point?

A: In short, yes, divide and replant ASAP. You can find additional information on planting and caring for garlic in Maine at Growing Hardneck Garlic in Your Maine Garden.

Q: We have built three, 5’x10’x10″ raised garden beds, and are now trying to figure out the appropriate soil mixture for optimum growth for our vegetables. I have read that a good combination is 50% compost, 25% sphagnum peat moss, and 25% sand. Does this seem okay to you? In using sand, what type of sand should I be using?

Raised beds by Dennis ConnellyA: For raised beds, we suggest a mix of 75% screened loam and 25% finished commercial compost (not composted manure). Many compost suppliers and nurseries deliver this kind of “gardener’s mix” by the yard. (Some mixes are 50% loam, 50% compost, which is okay.) Peat moss will work for part of the organic matter component, but it’s very expensive, tends to repel water, is mined from a finite resource, and provides very few nutrients.

Once you fill the beds, it might be wise to test your soil. Your soil test results will come back with nutrient readings so you will know what you might need to add during the growing season and also whether you need lime or sulfur to raise or lower the pH. You can pick up soil test kits at any county Extension office. We can also mail one to you.

This soil volume calculator can help you find what you need to order.

Information about raised bed gardening can be found at Gardening in Small Places.

Visit our website for information about an upcoming raised bed gardening program in Springvale.

septic leach fieldQ: What is a safe distance to plant from a leach field? The area is gently sloped for about 25′ then there’s kind of a mound parallel to the length of the leach field. Behind it a seasonal wetland that drains to a salt water cove.

A: Please see Bulletin #2442 Vegetable Gardens & Septic Fields Don’t Mix for detailed information about planting near leach fields.

Q: If there is a large vertical space between sets of branches (whorl?) in a spruce tree can the tree be made fuller by pruning the existing branch ends?

A: In response to your question, please do not prune the existing branch ends – this is called shearing and contributes to the overall decline of evergreens when done consistently. Shearing can provide a flush of ‘filling in’ but is not a long-term solution. If the tree has reached the height you would like it to be, removing the central leader promotes internal branching and greater density in the tree – giving you the fuller look you desire. This technique works best if you remove the leader just as the tree has reached its ideal height and still has ‘young tissue’. If the spruce has developed old wood, and depending on how old this Spruce is, that may not work. Older wood does not have active buds that would emerge and grow upon pruning.

Please take the time to read and process both of these resources, Pruning Evergreens in the Landscape (PDF) and Pruning Woody Landscape Plants.

As a general rule, prune evergreens with more caution and less drastic cuts than you would apply to deciduous plants, due to evergreen’s slower growing nature. Light, periodic pruning — over several years — may be needed to remedy this empty space in the tree.

poorly formed raspberries on the vineQ: We have an issue with raspberries. We get fruit, but for several years many of the berries are not complete. The attached photo is typical. Is this just a lack of pollination? Could this be related to soil acidity or nutrients?

A: It is due to lack of sufficient pollination. Here’s a good article about it, The Importance of Pollinators. The article also gives information on how to cultivate more native bees and bumblebees (excellent pollinators of raspberries).

Q: I am looking for recommendations for landscape trees in front on my recently-built home. We are looking for a single trunk with lacy see-through foliage (not wanting to block the home views) and hopefully slow growing. The current trees fit the bill aesthetically — Himalayan Birch — however, they have a borer disease as diagnosed by a tree specialist. I am willing to try again with the same type of tree, but want to explore other options, too, and am looking for recommendations for this unique location. I also plan on installing an irrigation system this spring to counter the summer dryness. The planting bed around the trees is mulched.

A: I think you’ll find our bulletin about Maine’s native plants helpful. It gives a plant list with light and moisture requirements, expected height, and comments about conditions in which the plant grows. You’ll need to scroll down a bit to reach the plant list, which starts off with trees but also includes shrubs, ferns, flowering plants, etc. Our bulletin about nurseries and garden centers offers resources on native plants (wholesale and retail).

When considering a new tree for my landscape, it’s helpful to see the plant in person before settling on anything. Scan the native plant list for some possibilities given your conditions, and then head to a local nursery to view them. Individual tastes can vary so much that it’s important to view the plants in person to select what you like.

late blight on tomatoes
Tomato plants infected with late blight.

Q: I’ve been dealing with early blight the last few years, resulting in a very low output of tomatoes. My four raised beds are in close proximity to one another. A local master gardener recently told me I should forget about trying to grow tomatoes for three years in these beds. I assume this will enable the fungi (or spores) to dissipate. Does this sound right? Can I try to grow tomatoes elsewhere in my backyard? If I use a new raised bed, how far from the blight-infested beds would it have to be placed? Is there anything I could do to the soil in the beds to help eradicate the early blight? Lastly, should I get rid of the metal cages I’ve been using, thinking the fungi may be on the exterior of the cages? Should I wipe the cages down with bleach perhaps?

A: See Early Blight of Tomato for an overview of how Early Blight spreads and how to manage it. Another excellent article that highlights some additional information is management and resistant cultivates.

To get a bit more into the weeds, disease management is about removing at least one element from the disease triangle, so that the disease doesn’t take hold. All three aspects (susceptible host, pathogen, and conducive environment) must be present for the disease to get established. In many cases, all three aspects must be present AND for a certain length of time.

This may help you understand better the disease management instructions given at the Early Blight links above. Those management practices are ways to reduce/eliminate at least one element from the disease triangle. Your best bet would be to implement several of the management practices at once. I would recommend, at least:

  • using crop rotation (not planting tomatoes or potatoes in those raised beds for 3 years),
  • cleaning up any leftover crop residue at the end of the season
  • conduct a soil test and follow its recommendations. Remember that too many nutrients can be detrimental to the plant and the environment, so please test
  • keep plants well watered – and mulched
  • and, if you wish to plant tomatoes elsewhere in your garden – select resistant varieties. Since it is a fungus and travels readily by air, you won’t be able to plant your plants far enough away to not have the spores reach them.

Resistant cultivars
There are many resistant tomato cultivars available, often designated with an “EB” in seed catalogs. There is also an extensive list of resistant cultivars on Cornell University’s vegetable pathology website. Resistant varieties are not immune to early blight. Rather moderate levels of resistance to either leaf infection, stem infection or both are present.

A few common cultivars with early blight resistance include:

  • Iron Lady
  • Mountain Supreme
  • Mountain Magic
  • Defiant PhR
  • Jasper
  • Juliet
  • Verona

You don’t need to get rid of the metal cages you have, but I would sanitize them with bleach.

rows of lettuce plants; photo by Edwin RemsbergQ: What variety of lettuce is the most heat tolerant? My grandson would like to grow lettuce in Jamaica but the hot weather may cause plants to bolt.

A: Your best bet is to reach out to one of the nearest Cooperative Extension offices in either Puerto Rico or the US Virgin Islands to see what they suggest.

Since lettuce is a cool season crop, you may have to try and grow it only during your cooler months of the year. Other techniques would be to use some shade and mulch the garden soil to try and keep it moist and cool.

Q: Would you give me approximate time to start seed plants so they are ready to go into my garden?

tomato seedlingsA: The timing of when you start seeds indoors will depend on the type of crop you are growing and the frost free date for your area. Enter your zip code on this website to determine an estimated frost free date for your region and use Johnny’s Seed Starting Calculator to determine when to start a variety of crops. For more information, see Bulletin #2751, Starting Seeds at Home.

For central Maine gardeners, here are some crops you’ll want to consider starting soon:

Late March: hollyhock, snapdragon, stock, artichoke, kohlrabi
Early April: pepper, eggplant, broccoli, cauliflower, cabbage, beets*, coleus, status, impatiens, larkspur, cosmos, sweet pea*
Mid April: lettuce*, calendula, marigold, tomato, basil
Late April: chard*
Early May: cucumber*, melons*, sunflower*, morning glory*, zinnia, squash*, pumpkin*
Mid May: broccoli**, Brussels sprouts**, cabbage**, cauliflower**

* usually direct sown, but may be started indoors
** for a fall crop

Q: My two 7-year-old plum trees are growing vigorously, but I haven’t been able to harvest any plums. Each spring there are plentiful blossoms followed by lots of tiny growing plums, but they don’t seem to get much bigger than an olive before they drop off the branch. Any idea why?

A: Possible causes of premature fruit drop in plums include:
  • Plum curculio damage. See images and management options here.
  • Insufficient moisture or underdeveloped root system. Solutions include irrigation, mulching, and thinning fruit crop before it develops.
  • Flowers not fully fertilized. Identify what variety of plum you have, check out this piece on pollination requirements, and reconnect with us if you need help determining whether it needs another pollen source.
More information on planting, early care, pruning, insect/disease management and more can be found on our Growing Fruit Trees in Maine website.

Q: Looking for some help on growing vegetables hydroponically. Are there any classes or anything that would help me with that?

A: I don’t know of any workshops being offered by Extension in the near future, but I encourage you to reach out directly to your local county extension office to see if they know of any community partners who might be holding a workshop in your area.

Here are a few helpful resources on the topic:

Don’t hesitate to reach out to your local office if you have any further questions.

sowing seeds in pots
© Lisa Looke, Photos courtesy of Wild Seed Project

Q: When is the best time to start growing seeds indoors? What time of year is the last frost? Do I also need to start lettuce and spinach indoors?

A: To find the right time to start seedlings for your region, work backward from the average last frost date. Go to the following website where you can hover your cursor over your town. This will give you the average last spring frost date. (Just to be clear, there is STILL a 50% chance that a frost will occur after that date, so be careful and protect your fragile seedlings)!

Seed Starting contains information on when to start seeds based on when you want to set seedlings out in the garden. Your seed packets will have more information on the back about the number of weeks before transplanting to start a particular vegetable.

Spinach and lettuce seeds can be sown directly in the ground, or started ahead of time as seedlings. They are tolerant of cooler temperatures, and can be put in the ground three to four weeks before your average last frost date, as long as your soil has thawed and drained its excess water.

For frost-sensitive (warm season) crops such as tomatoes, peppers, cucumbers, squash, beans, and corn, wait to set them out until ALL danger of frost has passed. That could be as early as your “average last frost date,” but watch them closely and prepare to cover them if a frost is predicted or, to be safe, wait until Memorial Day. For pepper plants, wait until the second week June before setting them out. They are very sensitive to temperatures below 50 degrees Fahrenheit.

Q: I’m originally from Kentucky and I’m finding it hard to find mustard greens in the Augusta area. Can I grow them in my Maine garden? Is there a particular variety that you recommend?

A: There are several different types of mustard greens that can easily be grown in your Maine garden. They are a cool season crop, and can be directly seeded in your garden as soon as the soil can be worked in the spring. Because our summers remain relatively cool, mustards can be grown in succession plantings through the entire growing season into the fall. Here is a link to a bulletin from Utah State Cooperative Extension on growing Mustard in the Garden (PDF).

Here are links to Maine-based seed companies from whom you can order a variety of mustard seeds:

Q: We filled in an in-ground swimming pool with sand last year. We now want to use that area for gardening. What type of soil and how deep would it need to be to grow vegetables? (We know we’ll have to take out some of the sand but hopefully not too much, especially in the deep end.)

woman weeding vegetable garden; photo by Edwin RemsbergA: I suggest you replace the sand with 18″ to 24″ of screened garden loam mixed with compost. This can often be purchased by the cubic yard from a local nursery or landscaping business, which is much cheaper than buying it in bags. If you are growing vegetables, make sure the loam is not mixed with composted municipal solid waste. It would be a good idea to have a soil test done on the loam before you start gardening in it, so you know what you are working with and whether or not it needs amending to adjust the pH or nutrient levels. Please realize that where the loam meets the sand beneath it, due to a change in soil texture, water drainage will slow down. It is best not to have a dramatically different horizontal layers in the soil, so if you can “feather” some of the loam into the underlying layer of sand where the two meet, it would ensure better drainage.

Q: I just purchased a greenhouse and am wondering how soon I can put seedlings in it? It will be unheated and is approximately 6 feet by 8 feet. I live in Rockport. I plan on starting seeds inside my home and then move the seedlings to the greenhouse when it’s warm enough.

Also, I grew kale from June to October last year and in September I noticed that aphids and the green cabbage/broccoli worms were starting to show up in large numbers on the kale. Is there anything I can do to the soil before planting to help prevent them coming back?

A: Seedlings of cool season crops (kale, cabbage, etc.) can go into an unheated structure in early- to mid-April. Warm season crops (tomatoes, peppers, melons, cucumbers, etc.) can go in late April to early May. In both cases, daytime temperatures inside the greenhouse will need to be closely monitored, especially on sunny days. Daytime temperatures can easily reach dangerously high levels if the house is not vented. Seed germination can be hastened by use of a root zone heating mat. This will also allow earlier starting of seedlings as the root zone heat will protect plants early in the season.

There are no effective soil treatments for aphids and cabbage worms. Cabbage worms can be managed by using light-weight row covers to prevent adults from laying eggs on the plants. Routine scouting for both pests can be used to effectively time your control measures.

Q: Can I legally grow currants in Sangerville, Maine?

White pine infected with White Pine Blister RustA: It is illegal to possess, transport or sell Ribes plants (currants and gooseberries) in most areas of Maine, including Sangerville. White Pine Blister Rust (WPBR) is a serious disease of white pine, a major forest and economic species in Maine. This disease weakens and kills infected trees and can prevent the regeneration of white pine in some forest areas. Ribes species play an important role in the survival and spread of the disease. Infections of WPBR cannot be passed from pine tree to pine tree, but must infect a Ribes plant to spread to pine. See Towns Regulated by Maine’s White Pine Blister Rust Quarantine (PDF) for a map and a complete list of Maine towns.

For more information on State forestry related quarantines in effect in Maine, visit Quarantine Information.

Q: Last year I planted two nut-bearing walnut trees. I don’t recall if they were either English or Carpathian. I just learned that black walnuts have a natural poison which effects many plants nearby. Are other walnut varieties as toxic as the black? Mine are not near the vegetable garden, but I was hoping for a flower garden nearby. Also is the spacing of 20 feet correct?

walnuts ripening on tree
Photo courtesy: Robert Vidéki, Doronicum Kft.,

A: English and Carpathian walnut can reach 40′ to 60′ in height with a comparable or greater spread at maturity, so your 20 foot spacing is a little tight. In the long run, if you do not want their canopies to overlap at maturity, they would be better off spaced 30 feet apart. For more information on Carpathian walnut, which is a variety of English walnut, see this fact sheet from the University of Idaho (PDF).

They do produce the allelopathic chemical juglans, but not in the same concentration that the black walnut produces. Highest levels are in the root system and in the nut hulls. See the following links for more information, and suggested lists of plants that are resistant to juglone:

Q: We’re having issues with our kale; it’s showing leaf scorch on its apical meristems. We have green curly kale varieties (mostly Winterbor, Darkibor, and Starbor) as a winter harvest crop in our unheated high tunnels. They were planted back in September and were mature when we began harvesting them in late December. Our kale has been under high hoops with three layers of Agribon floating row cover. Layers have been removed or plants uncovered as needed based on fluctuating temperatures and cloud cover. Despite our monitoring and considerations in management, the majority of our green curly kale plants, especially those planted on the southern end of the high tunnel, have suffered weakening of stems/leaf veins and browning/necrosis of leaf tips and of those new leaves emerging from the meristem. We’re wondering if it’s the fluctuating temperatures or extremes that we might not be anticipating in our management of the tunnels. What could be causing this leaf burn?

A: Fluctuating temperatures could and would be a cause of leaf burn along the margins at this time of year. Though Kale is a very hardy green, it is not as hardy to the extreme cold temperatures we get in mid-winter as spinach would be. The cold won’t kill it but can burn the margins which would make it less valuable to market. The good news is as we get into February and the days start to lengthen there will be a lot of new growth that should be a nice lush dark green without the leaf burn. You could cut the kale back and let it come up clean since we are now getting into the longer days.

I have grown kale myself in a winter greens small moveable greenhouse and have experienced the same thing. A couple of nights on 5-10 degrees below 0 is enough to cause leaf burn. I have tried a lot of different winter greens and by far the most hardy and resistant to burning is spinach. You just can’t kill it. For mid-winter in an unheated high tunnel spinach could be a more marketable winter crop, with kale planted for late fall and late winter harvests knowing that you may still experience some leaf burn in mid-winter.

You could also send specimens to our Insect and Plant Disease Diagnostic Lab at 491 College Avenue, Orono, ME 04473 for analysis, to make sure it is indeed an environmental cause (extreme low temps) causing your problem and not a disease.

Q: I live in the lower part of Washington County along the coast. What’s the right time to start vegetables indoors for spring transplanting? What vegetables would your recommend for this?

seedlings on indoor growing racks
Photo by Joe Bergeron.

A: To find the right time for your region, work backward from the average last frost date, which for you would be approximately May 14th. For frost-tolerant (cold hardy) crops like lettuce, peas, carrots, spinach, and kale you can subtract 3-4 weeks and set those seedlings out as early as late April/early May. For frost-susceptible (warm season) crops such as tomatoes, peppers, cucumbers, squash, beans, and corn, wait to set them out until danger of frost has passed. That could be as early as May 14 if you watch them closely and prepare to cover them if a frost is expected or, to be safe, wait until Memorial Day.

Seed Starting contains information on when to start seeds based on when you want to set seedlings out in the garden. Your seed packets will have more information on the back about the number of weeks before transplanting to start a particular vegetable.

As to what to grow, the choices are unlimited and really depend on what you like to eat. There are recommendations in Vegetable Varieties for Maine. If you check seed catalogs, there are many more varieties and crops you could choose from and more varieties are added every year. Using a Maine Seed Catalog like Johnny’s Select Seed, Pinetree Seeds, or Fedco Seeds would ensure you get the right varieties for Maine.

green tomatoes on the vine; photo by Edwin RemsbergQ: What is the best time to plant tomatoes in Boothbay Harbor?

A: The frost-free dates for Bar Harbor (closest I could find to Boothbay Harbor) are May 17 to October 3.  Since tomatoes are a warm season crop, you should definitely wait until after May 17 to plant your tomato plants. You may want to wait until Memorial weekend to be sure or look at the 10-day forecast for your area to see what risks you might be facing in a particular year if you plant that early and be prepared to cover the plants if the temperature dips unexpectedly.

Q: I have a flowering tree, maybe a type of dogwood, that has grown through my rock wall along the stream beside my home. It is slowly dying and I would like to save it or, if needed replace it for the shade and retaining qualities for the rock wall see photos I would appreciate any thoughts.

trees growing along a streamA: It is hard to tell from the pictures what might be wrong with the tree. The big tree looks pretty healthy and also looks like a maple tree. The smaller tree is hard to identify from the pictures. Trees can suffer from a number of issues: drought or too much water, lack of fertilizer, too much fertilizer, lawn fertilizer that contains an herbicide, lawnmower damage, late spring frosts, and even old age.  Any of these causes might be having an impact on tree health. If you can discover the cause, you may be able to address the cause and preserve the health of the tree. If not, as in the case of old age, you may need to replace the tree with another option. Some trees that would do well in Maine include the natives Alnus rugosa or speckled alder in wet sites, Amelanchier arborea — Juneberry, Amelanchier laevis — Allegheny serviceberry, Hamamelis virginiana — common witchhazel, and Cornus alternifolia — pagoda dogwood.

blueberries on bushQ: My blueberry bushes have not bloomed yet. How long does it take?

A: Your blueberry bushes should start blooming right away, assuming you purchased them as a 1-3 year old plant. Usually, it is recommended you pick off the blossoms the first couple of years. They may not have bloomed if the soil pH was not right or they didn’t get enough sun. For more information, see Growing Highbush Blueberries.

Q: Last year, I grew a small variety of heirloom and hybrid tomatoes. My husband and I also grew several potato varieties as well. I was just wondering if you had any suggestions to increase our yield for 2017 with a new tomato variety. For tomatoes, we grew: Cherokee Purple, Big Zac, Rapunzel, Azoychka, Abe Lincoln, Carmello, and a few more. The only varieties that produced well for me were: Big Zac, Carmello, and Rapunzel. I did save my Carmello seeds and I will be planting them again this year, but I was wondering if there were any high producers that were heirloom tomato varieties that you would recommend? Last year, we also grew Yukon Gold, Magic Molly’s, and White Kennebecs for potatoes. Is there an early potato heavy producer that you would recommend?

vine ripening tomatoesA: It looks like you are growing a great variety of tomatoes. If you like heirloom tomatoes and cherry tomatoes in particular, I would suggest Matt’s Wild, which is a very prolific producer. I would also suggest Juliet, which is not an heirloom but a very reliable producer in all sorts of conditions. For potatoes, Caribe, and Red Norlands are reliable early season varieties.

Questions & Answers from 2016

Questions & Answers from 2015

Questions & Answers from Previous Seasons