Got questions about gardening 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


2020 Q&A

Answers are provided by Donna Coffin, Extension Professor, Penobscot & Piscataquis Counties; Caragh Fitzgerald, Associate Extension Professor, Agriculture, UMaine Extension Kennebec County; Kate Garland, Horticultural Professional, UMaine Extension Penobscot County; Pamela Hargest, Horticulture Professional, UMaine Etension Cumberland County; Kathy Hopkins, Extension Educator, UMaine Extension Somerset County; Tori Jackson, Extension Educator: Agriculture and Natural Resources, UMaine Extension Androscoggin and Sagadahoc Counties; Marjorie Peronto, Extension Educator, UMaine Extension Hancock and Washington Counties; Elizabeth Stanley, Horticulture Community Education Assistant, UMaine Extension Knox, Lincoln, and Waldo Counties; and Frank Wertheim, Extension Educator, Agriculture/Horticulture, UMaine Extension York County.

Q: I have received bare root trees from the Arbor Day Foundation: American Redbud, White Flowering Dogwood, and Crape Myrtle. I live in Alfred (York County). The directions indicate to plant “from the time frost first leaves the ground.” It seems too early to plant them. How do I best store them? Need I wait to plant until we are past the frost-free date for my area?

A: Those are going to be some beautiful trees in your yard! Bare-root trees are dormant, so you don’t need to worry about the cooler temperatures as much as you would for an actively growing tree. Here are the recommendations for planting bare-root trees is the spring from UMaine Extension Bulletin #2366, Selecting, Planting, and Caring for Trees and Shrubs in the Maine Landscape:

Bare-root plants are typically available only in early spring before the buds begin to swell. Since these plants’ roots are bare, it is critical to keep them moist by packing their roots in moist material, such as sawdust, or covering their roots with wet burlap. Store the plants in a cool location (32 to 40 degrees F is best), and plant as soon as possible, before the roots and buds start to grow.

Plants available in nurseries in early spring with their roots wrapped in damp sphagnum and packed in cardboard or plastic containers are also bare-root. When planting, spread their roots out to a natural position.

It is important to plant bare-root trees and shrubs soon after you get them. Anticipate their arrival. Dig planting holes ahead of time. Keep roots moist but not wet by covering them with wet burlap, and do not hold them longer than a few days before planting. Just before planting, soak roots in water for six to 12 hours.

Q: Is there a list of sources of composted manure in Maine? I live in the Ellsworth area.

A: While we do not maintain a list specific to composted manure, we do have a list of commercial composters that folks have volunteered to be added to. You can download it, Commercial Compost Suppliers in Maine (PDF). If you are looking specifically for composted manure, I recommend calling local farms to see if they might sell you some from their pile and then hold it until Fall for application to your garden. If you don’t need a lot, you can buy it bagged from most garden centers. For more information about the safe application of manure on vegetable gardens, I recommend reading Bulletin #2510, Guidelines for Using Manure on Vegetable Gardens.

Q: I have an older shallow well on my property in Falmouth. Can I safely use this to irrigate a garden? Any concern to vegetable crops based on radon or arsenic for example?

A: All well water should be regularly tested as groundwater is changing all of the time. Any time you are putting a new water source into use, we recommend getting a water test first. Arsenic in groundwater is a concern for many people in Maine and testing for it as well as other potentially harmful materials is an important step to determining exactly what is in this water. You can order a test kit online from the Maine Health and Environmental Testing Lab in Augusta. If (when you receive your test results) everything looks fine, we recommend trickle or drip irrigation to conserve water, which might be particularly useful in a shallow well that may be more prone to running dry in the summer.

Q: I live in Mid-Coast Maine, in the town of Southport, and would like to plant a pollinator garden. I’m looking for a list of both annuals and perennials that would be best for my location. I buy my flowers in my area’s greenhouses/nurseries. I’ve read that some flowers have been so developed for appearance, etc. that their pollinator quality has been diminished. Even using your recommendations, how can I be sure the flowers I’m buying are good for pollinators and have not had this quality diminished?

Monarch on goldenrod
Photo by C. Eves-Thomas

A: There is a lot of energy around planting pollinator gardens these days. In fact, UMaine Extension is launching a brand new pollinator garden certification program and website to help folks modify existing plantings to become more pollinator friendly, or create one from scratch with pollinators in mind. Until we are ready to launch (hopefully, in April 2020), I can direct you to our list of Plants for Pollinator Gardens to help you get started in choosing native plant species that will support your native pollinators. Our friends at the Wild Seed Project have a great blog post on native asters and goldenrod specifically. Whenever you prioritize native plants, pollinators will be supported.

Q: Do you have any advice on pruning for limiting the height of Norway spruce trees? Should I nip the leaders above a bud and should I do so well in advance of the trees reaching ideal height, or wait until they’re almost there, or is it something that should be done regularly, like every couple of years?

A: I’m afraid my response is not what you are looking for, but here goes. If height is an issue, it might be preferable for you to remove the tree and replace it with something that doesn’t get as tall. If you go to a reputable nursery you should be able to obtain a dwarf evergreen tree or shrub that better suits your needs. A mature Norway spruce can grow to a majestic 40′ – 60′ in height, with a spread of 25′ to 30′. They are stunning. Topping the tree will allow it to get fatter over time but not taller, destroying its natural habit. You will have to shear the top once or twice a year to keep the height where it is, and you may not get the results you are looking for. Here is a good bulletin on the drawbacks of topping trees to control height from Purdue University: What’s Wrong with Topping Trees? (PDF).

Q: I am trying to discover the best way to transplant a small but mature apple tree. I have a tree in my yard that I would like to move. It’s at least 10 years old, about 12 feet tall, with a trunk diameter of maybe 5 inches. I’m convinced it needs to move because it is in shallow soil (8 inches) over bedrock. Its root system is very close to the surface and reaches maybe 20 feet out from the trunk.

I’ve read that with regular landscaped trees that I should root prune in the previous growing season to encourage roots to develop close to the root ball and then transplant the following spring. Is this general advice applicable to apple trees? Should I also more heavily prune the canopy to reduce the nutrient and water need of the tree so root pruning doesn’t kill it and to reduce transplant shock next year? Is there any simple guidance you could offer me or a resource that might be useful?

apples on treeA: After conferring with our tree fruit specialist, I have the following to offer. Moving a mature apple tree is a risky proposal, but it could work if the tree is moved in May. Root pruning one year prior to moving the tree would increase the chance of survival. However, if it has a taproot, the chance of success is not good. Understanding that the tree could die, you may want to leave it in place and start over by planting a new young tree in a better location. When the new tree begins bearing fruit, then you can remove the old one. The labor involved in moving a mature apple tree outweighs the expense of planting a new one.

There are no guidelines regarding size of root ball, because this has not been studied with mature apple trees. That said, the International Society of Arboriculture recommends the following for moving landscape trees: “When a tree is dug for transplanting, the size of the root ball is traditionally based on tree caliper. Measure tree caliper 12″ above the ground for trees more than 4″ in diameter. A rule of thumb for the width of the root ball is 10 to 12″ per inch of trunk diameter.” If your tree trunk has a 5″ diameter, the root ball should be at least 4′ to 5′ wide. In general, a root ball depth of 30 to 36″ is sufficient for most species. In your case, since your tree is growing in shallow soil over ledge, the ball will be much shallower.

Root pruning is the process of pre-digging a root ball to increase density of root development within the final ball. The digging process severs existing roots and stimulates root regeneration. Root pruning may be repeated multiple times before the tree is actually moved. Each successive cut is made several inches out from where the roots were previously severed.

You do not need to cut back the tree canopy to compensate for root pruning. Top growth will be temporarily reduced, but the tree needs as much photosynthetic tissue as possible to re-establish itself in a new location. Whenever you move a tree, you should make sure it receives 1″ of water per week during the growing season, until it is established. Establishment period recommended is 1 year per inch tree diameter, so in your case, it would be 5 years of regular watering for it to regain the proper root:shoot ratio.

Q: I live one hour north of Bangor. I’m starting seeds indoors. Some say start six or eight weeks before last expected frost. What is a general idea of when the last frost would be for my location?

flats of seedlingsA: Although the last frost date of the season changes each year, there is a calculator available for this in our Master Gardener Volunteer Manual based on your zip code.
According to that calculator (click on the blue type to see the calculator), it is unlikely that you will have a frost after May 14 or before September 29.

On the Johnny’s Seeds site there is a seed planting calculator that then shows by type of vegetable when to start the seeds and when to set them out.

It is important to realize that this information is based on data from the past and may not reflect the changing climate conditions we have had in the last few years. It is always a good idea to keep a journal of what happens in your garden and make a note each year what that frost date is for your garden.

Q: I’ve been searching the web for good step-by-step instructions for starting seeds using an LED array. I have a 600-watt array with toggles for blue and red wavelength light. My main question is how far the lights should be from the seeds trays and whether the distance should change as the seedlings develop true leaves. Can you recommend a helpful bulletin or other resource? (I’ve used fluorescent lights to start seeds for many years.)

A: LED lights sure are a more efficient way to provide the needed hours of light to your germinating plants.

The University of Mississippi has a short video that addresses this issue. In essence, there is little difference between using fluorescents and LEDs and no need to micromanage the light quality for small-scale production. However, there is some study in that area around large scale production done by the University of Michigan and in Japan. The report Growing Seedlings Under LEDs (PDF) might be helpful.

The distance issue can be addressed in our more traditional material as heat is not a factor with LED lamps. Seed starting and other propagation is addressed in our Master Gardener Volunteer Manual on Propagation and specifically in our Bulletin 2751, Starting Seeds at Home. In that bulletin, towards the bottom, is a video on building a seed starting stand and the height of the bulbs is addressed in there.  The most effective way to use any artificial light is to be able to keep it tight to the top of the plant (about 4″ above the plant) and then raise it as the seedlings grow. This way seedlings won’t stretch (and stress) during these vital first weeks of their life.

Q: I would like to plant sweet woodruff as a ground cover by broadcasting seeds. I understand the seeds need cold temperatures at the beginning stages of growth. What month should I attempt this here in Maine? Can there still be remnants of snow on the ground when I attempt this?

woodruff in blossomA: Sweet woodruff seeds require cold stratification for good germination success. Spring is not the best time to plant the seeds. You would have better success planting them in the late summer or early fall and allowing them to naturally stratify. If you wish to plant the seeds this spring, wait until there isn’t much snow cover, and try to get them on the ground as early as possible so they can get a period of cold. You will probably achieve very irregular germination, and it could take months for them to sprout. Sweet woodruff is more successfully propagated by plant division or by rooted cuttings.

Q: I’ve been growing raspberries for the past five years with much success until last year (2019). It was a wet and cold Spring and my raspberry bushes started later than has been normal. The plants themselves grew very nicely all summer, looked healthy and reached heights of 5-6 feet tall. The problem was there were no raspberries on any of the bushes so it leaves me wondering, what went wrong? I was speaking to a lady that owns an apple orchard last October and I noticed that four or five types of apples never came to fruition and when I asked her she told me that because of the cold and damp Spring some of her apple strains never got pollinated. Could this be what happened to my raspberries?

Killarney raspberriesA: Raspberry canes are biennial.  Flowers and fruits are produced on canes that are in their 2nd year of growth (floricanes).

If climate conditions caused last year’s overwintering canes to die, the new vegetative growth you observed last summer were most likely 1st year canes (primocanes) growing up from the crown of the plant. These primocanes that grew last summer should produce fruit in the coming growing season.

I’m wondering if by chance someone mistakenly pruned out your floricanes before the growing season began last year?  It seems highly unlikely that they would all succumb to disease or winterkill. But if you saw no flowers, you did not have floricanes in your patch. Thus, no fruit.

See the following bulletin, Growing Raspberries and Blackberries for detailed information on how to grow your best raspberries in Maine.

Q: We are in the process of planning for a rain garden installation at our school. We would love some advice on how much soil to excavate and what to back fill with.

rain garden plants
Rain garden plants.

A: When digging your rain garden, loosen the soil at least two feet deep. Even though the garden will only be six inches deep in the center, loosening the soil will help your plants establish root systems in this new environment. For much more detailed instructions, including how to select a location and which plants to install, check out UMaine Extension Bulletin #2702, Landscapes for Maine: Adding a Rain Garden to Your Landscape.

Q: Do you measure lead levels in eggs? If so, how do I go about getting this done?

A: This page is for vegetable gardening questions, but you can contact the UMaine Extension Veterinary Diagnostic Laboratory for information about submitting eggs for lead testing. Be sure to call 581.3874 before preparing anything for submission to be sure you follow the instructions.

Q: How can I grow Ilex verticillata (winterberry) from the berry (seed)?

A: In answer to your question about growing Winterberry, Ilex vertillata, you can use the berries from current plants. If the berries are still firm enough, put them in a plastic bag and let them ferment. When soft enough (might take a week) to squish, separate the clean seed. Place the seeds in a pot, it is pretty tolerant of soils but it does grow in acidic soils in nature.  Sprinkle sand (builders sand is best) over the top to cover. Place the pot(s) outside, it will need about 6 weeks of cold temperatures, out of direct sun so it doesn’t dry out. This a very slow growing shrub, and it may take until the following Spring before a new shoot appears.

For more information to keep in mind about adding Winterberry to your landscape read, Native Trees and Shrubs for Maine Landscapes: Winterberry (Ilex vertillata).

Q: I have well established vegetable garden beds, but am planning an extended trip this summer. I would like to plant a cover crop that can be turned over for green manure. Which plant do you recommend?

A: If you are leaving over the summer you will want to plant a crop that does well in the heat. One that does well in summer, is suitable for a home gardener and is a great weed competitor is buckwheat. Buckwheat will flower in about 6-7 weeks after seeding. It should be plowed or tilled in while flowering and before setting seed, because then you would be fighting it as a weed species the following year. So if you are going to be gone longer than that you may want to have someone till it in and follow that with a crop of oats. The oats would winter kill and you will have a nice dead mass to work with the following spring.

This Home Garden Cover Crop fact sheet will give you a broad idea of strategy to plan to meet your needs for the length of time you will be gone.

Q: I live on about three acres and had a dog until about a year ago. There was a portion of the yard in the back that we let grow up into a field and when I would go about cleaning feces out of the yard I would throw it in that field off and on. This past year we mowed the entire area. We never cleaned the area, but kept it mowed and I didn’t throw any more dog feces in the area. At present there are no dog feces present (just the occasional deer/random wild animal feces). I was wondering if that spot would be okay to use for our garden this spring or if the soil is now contaminated and unusable?

A: Since it has been a year since you have placed any of the dog’s waste in the field you wish to establish a garden in, it would be completely safe. By now any feces remains and associated pathogens should be well decomposed. The soil and its associated microbial life are excellent filters and decomposers. Our general guidelines for when animal/dog waste is found in farm and garden fields is to remove the waste and not to harvest vegetables or fruit that were in contact with it. With establishing a new garden now there would not be any remaining risk.

Q: I am looking for a reliable source for Russian Comfrey. Do you have any suggestions?

A: While I am not familiar with herbalists in the Freeport area who may carry it, there are several very good nursery/greenhouses in your region that should carry Russian Comfrey, which you can find from this comprehensive list of Nurseries and Garden Centers in Maine.

Q: I am new to Maine and building a new home in Damariscotta. I am installing a septic tank and leach field. I know not to plant woody plants, trees or vegetables. But what should I plant? What grass types are best for this region? Are wildflowers okay?

A: As our UMaine Extension fact sheet on Gardens and Septic Systems states, turf grasses are best suited for planting over a septic field. Any of the cool season grass mixes you would find in local garden centers would be suitable.

While wildflower mixes would also be generally suitable, you should avoid deep-rooted woody perennials that could potentially clog up pipes, and also be aware that wildflower natural areas are not easy to establish. Check the Native Plant Trust (formerly New England Wildflower Society) for a list of suitable wildflowers for New England and planting instructions.

Q: My Winterberry bushes are getting leggy and tall. I would love to have them bush out more from the bottom, grow thicker. Can Winterberry be cut back hard? When is the best time to do it, if so?

Winterberry
Photo by Richard Webb, Bugwood.org.

A: The natural habit of our native winterberry when it grows in the wild is quite leggy and open. When pruning, the objective is to enhance its natural habit rather than try to force it to be more bushy. Remove crossing, rubbing branches, and growth that is directed inward across the center of the plant. The goal is to obtain good air circulation and sunlight penetration throughout the shrub so that you will minimize disease and maximize flowering and fruiting. In my own experience, when I have cut winterberry back HARD to stimulate new growth, it has been quite slow to recover. Winterberries do not send out copious amounts of new shoots each year. If the plants are in full sun, they tend to send out more new growth each year than if they are in the shade. Some cultivars have a rounded habit and others are more open and broadly spreading.

There are dwarf cultivars (Red Sprite (female) paired with Jim Dandy (male)) that are more dense in habit than the straight species. If you want more visual impact from your winterberry planting, consider planting a drift of several shrubs together.

Q: A neighbor just brought me a Magnolia branch that broke off his tree. We live in Cushing, Maine. Can you advise me on what I need to do with this clipping/branch in order to plant it in the Spring?

magnolia blossom
Magnolia blossom. Photo by C. Eves-Thomas.

A: It sounds like the branch which broke off would be considered a hardwood cutting (that is a dormant, mature stem). The best type of cutting for rooting a magnolia would be considered a semi-hardwood cutting (partially mature wood of the current season’s growth, just after a flush of growth).

Having said that you can certainly give it a try.

Where it has broken off cut it again with a pruning clipper to get a nice straight clean cut at the bottom. You should dip the end in a rooting hormone which can be purchased at a local garden center. Then place the cutting in a plastic bag with some moist (not soaking) sphagnum moss or wood chips and place it in your refrigerator for the winter. In spring bury the cutting in your garden such that only the top few inches of the growing point are exposed.

A second method would be to treat the cutting with a rooting hormone as suggested above, and place it in a flower pot with vermiculite as your rooting medium. Well-drained potting soil can also be tried if that is what you have on hand. Moisten the medium well and place the pot and cutting in a plastic bag. Keep it in bright light but try to avoid direct sun and make sure it stays moist until rooting has occurred.

A more detailed description can be found in this fact sheet from North Carolina State University on Plant Propagation by Stem Cuttings.


Ask the Expert Q&A Archives