By Kate Garland, Horticultural Professional, UMaine Extension Penobscot County
Divide dahlias if you didn’t get around to that task last fall. This pictorial lesson offers helpful images and tips. Cuttings should be given approximately a week in dry room temperature conditions in order to heal over the wounds. Wait to plant dahlias until after the risk of frost has passed.
Harden off seedlings before planting. Home-grown and purchased seedlings greatly benefit from being gradually exposed to increased sun and wind as well as cooler temperatures. Simply move plants into more and more exposed sites over the course of a week or two while always being prepared to bring them indoors when nighttime temperatures are expected to dip. Many nurseries will begin this process for you. A good hint as to whether nursery seedlings are hardened off is where they are displayed. If they are outdoors, there’s a good chance they are hardened off or in the process of being hardened off. Still, it’s always a good idea to ask the staff if the seedlings you’re bringing home are ready to go in the ground.
Begin renovating overgrown and weedy perennial beds. Consider taking the “blank slate” method. Instead of constantly pulling the weeds growing around and up through your well-behaved perennials, lift the desirable perennials, carefully remove the weedy roots, divide anything that needs division, and temporarily replant in pots or in a separate holding area in your landscape. Then you can focus your attention on managing the weeds through repeated digging, covering, or a combination of those two strategies until it’s time to replant in late August. If the weeds persist, extend the battle until the following spring to establish a cleaner bed for replanting.
Sow an early-season cover crop to build soil organic matter. A mix of peas, oats, and vetch can be a winning combination to sow in early May, while late May can be a great time to sow buckwheat. Even if you don’t grow these crops to maturity (early August), they will improve the soil ecosystem and help suppress weeds.
Leave the leaves! Do you remember how we encouraged you to step away from the leaf rake last fall? A little more procrastination in the spring is also helpful for a variety of insects and other wildlife. Try waiting until late May to clean out formal gardens and taking the leap towards establishing some more natural areas that allow leaf litter to accumulate in the landscape.
Apply nitrogen to emerging garlic plants. Side dress rows with 1 tablespoon of bloodmeal (or an equivalent source nitrogen) for every six plants.
Use floating row cover or exclusion netting to protect crops from insects. While these coverings offer some protection from cold temperatures early in the growing season, they also can be very effective at keeping pests away from tender young plants. Be sure to cover crops as soon as they are planted, making sure all edges are tightly sealed. For crops that require pollination, remove covering when plants begin to flower. Some small-scale growers have even used this method to protect potatoes from the Colorado potato beetle.
Test your soil and follow the recommendations in the soil test report. We’ve said it before and we’ll say it again: the best approach to managing soil pH, nutrients, and soil organic matter is to send an aggregate sample to the Maine Soil Testing Service and follow their recommendations on which soil amendments to apply and when they should be applied. The standard test also includes a lead scan. It’s such a simple way to take a strategic approach to giving your plants just what they need to thrive. Watch the helpful video below and request a soil test kit.
Find a great gardening hat and/or keep a bottle of sunscreen handy in your gardening toolkit. On a personal note, I’ve known many gardening friends who have battled skin cancer over the years. While it’s nice to feel the warmth of the sun again, please take care of yourself!
And remember to always check for ticks at the end of the day.
Pollinator Garden at the Langlais Sculpture Preserve
Article and photos by Gail Presley, Knox-Lincoln Master Gardener Volunteer 2019
In 2018, the Georges River Land Trust partnered with Maine Master Gardener Volunteers to create a native pollinator garden at the entrance to the Langlais Sculpture Preserve in Cushing. The project took nearly two years to complete, but the results are amazing!
To enhance the welcoming feel of the Preserve’s entrance and take advantage of the space as an educational opportunity, the pollinator garden was designed for the 75 sq. ft. island in the parking lot. Much like “hell strips” in urban neighborhoods, such hot, dry locations can be difficult places for creating a self-sustaining garden. But as this garden demonstrates, such areas need not be relegated to grass or gravel. An otherwise dead zone can become a native plant oasis and a healthy, colorful host site for important pollinators and birds.
Over the fall, winter, and spring of 2018-19, we covered the site with opaque plastic to suppress weeds. In July 2019, we removed the plastic and planted a cover crop of buckwheat. Buckwheat grows quickly, germinating within days and flowering within four weeks. It provides dual benefits: nectar for bees and butterflies, and dense cover to suppress weeds while improving soil health. We identified more than 14 species of pollinators using the buckwheat: bees, bumblebees, hoverflies, hornets, yellow jackets, butterflies, lady beetles, and more! In late August, the buckwheat was cut before it could set seed and left to add its nutrients to the soil.
The project had three design goals: use native plants (PDF) to feed pollinators and birds, use plants that can survive without supplemental water once established, and create a beautiful garden that would be in bloom from early spring to late fall. The planting design (PDF) includes a range of flowering plants with different seasons of bloom, height, and color, and also includes grasses for visual interest and seeds for birds.
In September 2019, we planted more than 260 seedlings, plugs, and transplants of 19 native plant species, sourced from Maine Audubon’s Bringing Nature Home native plant program, a local native plant grower, and Master Gardener Volunteers. We watered the new plants and weeded as needed through the fall.
In summer 2020, we filled in spaces where there had been overwinter losses, using donated seedlings of six additional native species, and added a layer of compost and straw. And then we stood back and watched the show! It lived up to all our expectations hosting birds, pollinators, and beneficial insects, with beautiful waves of color all season. We even documented monarch caterpillars on their one-year-old milkweed hosts.
Be sure to visit next summer to see the garden in its prime. We are very grateful to the Maine Master Gardener Volunteers who helped with all phases of the project from design, donating plants, planting, weeding, and watering. Please consider supporting the good conservation work of Georges River Land Trust at Donate Now.
Using Row Covers in the Garden
By Nate Bernitz, UNH Home Horticulture Outreach Program Manager, Hillsborough County Office Co-Administrator
Row covers are an important tool for gardeners for season extension and pest control, sometimes dramatically reducing the need for pesticides while opening up weeks of extra growing time and helping speed up early-season plant growth. There’s no one way to use row cover, so it’s important to tailor your practice to the crops you’re growing, the time of year, and how much maintenance time you can invest.
What Is Row Cover
Row cover, also called floating row cover or spun-bonded row cover, is a lightweight and gauze-like white fabric made from polyester or polypropylene. Row cover ranges in thicknesses. A lighter weight fabric might be labeled as .45 or .5 oz/sq. yd., whereas a heavier weight fabric might be labeled as somewhere between 1.5 and 2.2 oz/sq. yd. Row cover can be cut to size using sharp scissors, which is helpful because it typically comes in large rolls of varying widths and lengths.
Brands include Reemay, which is a spun-bonded polyester, Agronet, which is an ultraviolet-stabilized polypropylene and polyamide net, and Agribon, which is a spun-bonded polypropylene fabric. Other brands include Agryl, Harvest Guard, and Typar.
Using Row Cover for Season Extension
Used properly, row cover can provide frost protection in the spring and the fall while also supporting rapid plant establishment and growth. Row cover increases both temperature and humidity under the cover, and the amount of insulation depends on the weight of the row cover. A lightweight row cover might provide 2ºF of frost protection, whereas a heavy-weight row cover might provide as much as 6ºF to 10ºF of frost protection.
In the spring, when transplants are small, row cover can often be simply draped over plants without a frame. Row cover should be weighed down — bricks, stones, and garden staples are commonly used in a garden setting — but row cover can enable gardeners to experiment with pushing the planting window up by as much as several weeks in May. Used in this way, you can refer to the material as floating row cover.
For spring season extension, consider using row cover for tomatoes, peppers, eggplant, summer and winter squash, cucumber, pumpkin, melons, beans, greens, radish, broccoli, cauliflower, cabbage, kale, collards, chard, beets, potatoes, and strawberries. Once we get to early June, a heavy-weight row cover would no longer be appropriate. Flowers and fruits of beans, tomatoes, and peppers may abort when temperatures exceed 90ºF, and temperatures under the row cover could be as much as 15ºF higher than outside temperatures. Cool-season vegetables, like greens and brassicas (broccoli, cauliflower, cabbage, brussels sprouts, collards, kale, etc.) are also sensitive to warm temperatures and row cover should typically be removed by early June.
Temperature isn’t the only variable. For insect-pollinated vegetables, like the nightshades (tomato, eggplant, pepper) and cucurbits (squash, cucumber, pumpkin, melon), row cover should be removed when female flowers bloom so as to allow pollination to occur. Enterprising gardeners may consider removing the row cover in the morning when pollinating bees are most active and replacing the row cover in the afternoon and overnight.
The final consideration is when plants like tomato need to be staked or caged, and when plants like pole beans and vining cucumbers get too tall. At that point, row cover either needs to be supported with a frame or removed.
Other Season Extension Materials
Shade cloth, which may also be referred to as shade fabric, is typically a knitted or woven UV stabilized polyethylene fabric that blocks or reflects some amount of sunlight without re-radiating the heat onto your plants. Shade cloth comes in a variety of densities, ranging from 10% to upwards of 60%. Shade cloth reduces temperatures underneath the cloth, and if used properly, can support plant health and production in times of intense summer heat. While row cover would typically be used for season extension in the spring and fall, shade cloth would typically be used over the summer, either to extend the growing season for cool-season crops into warmer months or to protect warm-season crops like tomatoes and peppers from intense heat that could cause plants to abort flowers and fruit or experience physiological disorders like sunscald. With cool-season crops, the use of shade cloth could prevent greens, herbs, and brassicas from bolting or going to seed prematurely, and might also prevent some vegetables from developing a bitter flavor.
If you use shade cloth, it’s important to use a frame that creates some space between the plants and the cloth, which allows the cloth to work as intended as well as supports better airflow. If the shade cloth touches the foliage of the plant, you risk injury to the plant from direct heat transfer from the fabric to the plant.
You can also achieve shade in your garden through thoughtful design and companion planting, and protect plants from heat stress by fertilizing at recommended rates, using organic mulch, and watering early in the morning.
To protect from frost, alternatives to row cover include frost blankets, plastic coverings, and tarps. These materials should just cover plants at night, especially when temperatures drop below 30ºF. Double layers of materials will provide even more protection when temperatures drop below 28ºF. Whether you’re using row cover or an alternative covering, it’s crucial to weigh them to the ground, both to protect them from blowing in the wind and to prevent heat from escaping. With any kind of plastic material, ensure that the plant’s leaves aren’t coming in direct contact with the material, as that can lead to injury. Remember to take frost blankets, plastic coverings, and tarps off your plants during the day.
If you are looking beyond season extension and towards growing crops over the winter, you will want to consider cold frames or even a high tunnel.
Pest Exclusion and Management
When used properly within an Integrated Pest Management approach, row cover can create a barrier around your plants to exclude insects, as well as some animals like rabbits, birds, and deer.
General best practices:
Scout these plants frequently while the row cover is on your plants in the spring, both to check for pest and disease issues, check moisture levels, keep weeds under control under the row cover, and check temperatures to ensure temperatures don’t spike past 90ºF under the covers.
Remove row cover when insect-pollinated plants begin to flower.
Rotate crops each year, paying special attention to crop families to ensure you are rotating crops to a part of the garden where a crop of a different family was grown the previous year.
Pests that can be excluded with row cover, by crop:
Tomatoes and peppers: Aphids, cutworms, flea beetles
Eggplants and potatoes: Aphids, Colorado potato beetle, flea beetles
Broccoli, cabbage, cauliflower, and other brassicas: cabbage maggots, cutworms, flea beetles, cabbage loopers, cabbage worms
For vegetables that don’t rely on insect pollination, like beans, leafy greens, cabbage, and potatoes, you can replace row cover with a fine insect netting, which might also be called insect barrier. This material excluded insects without increasing temperatures or providing frost protection. It may block up to 10% of light, but that’s generally slightly more light transmission than row cover allows. Insect barrier is lighter weight than row cover and a valuable tool for heat-sensitive crops.
*UNH monitors squash vine borer and publishes data to guide decision-making in farms and gardens. Use this data to inform your use of row cover and other techniques for managing squash vine borer, and hand pollinate if necessary.
Establishing Row Cover and Frames
Before using row cover, mulch should be applied around your transplants to suppress weeds and retain moisture.
Drip irrigation or soaker hoses are ideal choices for irrigating crops under row cover. If your row cover is supported by a frame, you will have to peel it back to water, so drip irrigation or soaker hoses offer a far less labor intensive and more efficient way of watering your garden.
Supporting your row cover with frames allows you to keep your row cover on plants longer, and can likewise support other fabrics. Consider using either a low-tunnel design or an A-frame, both of which can be designed with either PVC piping, wood, or flexible wire such as electric fence wire or 9-gauge wire. Rebar is helpful for supporting low tunnels, although not necessary for a simple wire-based design, whereas you might use fence posts to support an a-frame. You can purchase these materials pre-fabricated from garden supply stores or as raw materials from local suppliers.
If you are creating frames for individual rows, plan for frame pieces to be spaced every four feet or so along the row, and target hoops approximately 16 to 20 inches high. For a 4-foot row, wire pieces should be about 6 feet in length. At the ends of your rows, consider using double-layered hoop pieces if you’re using wire because the row cover exerts the most pressure on the ends.
It’s helpful to be able to easily vent your row cover on warm days in the spring, so consider how you might peel back the sides. While peeling back the sides and venting your row cover allows pests in, it may be necessary on especially warm days without going through the hassle of completely removing the cover.
Maintaining Row Covers
If taken care of properly, row covers can be reused for several seasons. Store row cover in either sealed plastic bags or sealed containers. Do not leave row cover exposed in a barn, garage, or shed as mice may nest in the material. Treat your insect netting and shade cloth in the same way. While row cover is relatively inexpensive, it’s always better to use material for multiple seasons if you can as expenses add up quickly in the garden.
Part sun doesn’t mean part fun! This cheerful planter was spotted in an east facing window in Downeast Maine last fall. The orange Begonia ‘Glowing Embers’ pairs well with the purple Browaillia. Both shade tolerant plants complement the bold purple window trim.
Planting Chart for the Home Vegetable Garden
Developed by Lois Stack, Ornamental Horticulture Specialist, University of Maine Cooperative Extension
Crop
Average yield
Oz. seed / number plants per 10-ft row
Distance between rows (inches)
Distance between plants in row (inches)
Depth of planting (inches)
Planting date in central Maine*
Asparagus
6 spears/plant
6-7 plants
36-48
18
6-8
4/20 – 5/15
Beans, Pole
12 lbs/10 ft row
1 oz
36
24 (hills)
1
5/15 – 6/15
Beans, Snap
8 lbs/10 ft row
1-2 oz
24
2-4
1
5/15 – 7/15
Beets
10 lbs/10 ft row
1/10 oz
12-18
2-3
1/2
4/25 – 8/1
Broccoli
1.75 lbs/plant
6-7 plants
24-36
24-30
—
5/1 – 8/1
Cabbage
3/4 – 3 lbs/plant
6-7 plants
24-36
12-18
—
5/1 – 8/1
Carrots
10 lbs/10 ft row
1/20 oz
12-18
2-3
1/2
5/1 – 7/15
Corn
20-24 ears/10 ft row
1/2 oz
24-36
6-8
1
5/15 – 7/1
Cucumbers
10 fruits/plant
1/20 oz
48-72
48 (hills)
3/4
6/1 – 7/15
Eggplant
4-5 lbs/plant
6-7 plants
24-36
18
—
6/1 – 6/15
Onions
1 lb sets yields 30-40 lbs onion
1/10 lb
12-18
1-3
1/2
4/20–5/15
Parsnips
15 lbs/10 ft row
1/8 oz
18-24
2-4
1/2
5/1 – 5/15
Peas
10 lbs/10 ft row
1/10 lb
18-36
1-2
1
4/15 – 7/15
Peppers
6-12 fruits/plant
6-7 plants
18-24
18
—
5/25 – 6/20
Potatoes
5 lb seed potatoes yields 50 lbs potatoes
2 lbs seed potatoes
30-36
8-12
4-6
5/1 – 6/1
Pumpkin
4-6 fruits/plant
1/10 oz
36
48 (hills)
1
5/20 – 6/10
Spinach
4-5 lbs/10 ft row
1/10 oz
12-18
3-4
1/2
4/10 – 5/10
7/1 – 8/1
Squash, Summer
15 lbs/10 ft row
1/10 oz
36
48 (hills)
1
5/25 – 7/15
Squash, Winter
10 lbs/10 ft row
1/10 oz
72-96
72 (hills)
1
5/20 – 6/10
Tomatoes
8 lbs/plant
3-6 plants
24-48
18-36
—
5/25 – 6/20
Turnip
25 lbs/10 ft row
1/30 oz
12-18
1
1/4 – 1/2
5/1 – 8/1
*In coastal Maine, plant 10-14 days earlier. In northern Maine, plant 10-14 days later. The two dates given represent the earliest and latest safe dates.
Testing for Lead in Maine’s Soils
By John Clark, Environmental Steward
The Cumberland County Soil and Water Conservation District (CCSWCD), in partnership with the EPA, is working to spread awareness of soil lead contamination. Part of this includes testing soil and plant tissue to identify lead risks for gardeners in urban areas. As part of this grant, CCSWCD is providing free soil tests to gardeners and anyone interested in gardening in the Bayside, East Bayside, Parkside, or West End neighborhoods of Portland.
Soil tests are highly recommended for anyone growing food in these neighborhoods to identify possible soil contaminants, especially lead.
Based on Portland’s historical use in these neighborhoods, there is a high chance that soils here are contaminated with lead. Lead concentrations over 100 ppm are cause for concern, while concentrations over 400 ppm are deemed hazardous by the Environmental Protection Agency. In 2020, the program collected 80 soil samples from these neighborhoods. Sixty-four percent of tests found lead levels that were higher than normal background levels. The average amount of lead found at these sites was 614 ppm, well over the hazardous level.
In addition to soil testing, 14 plant tissue samples were collected from edible plants grown in lead-contaminated soils to evaluate the impact of common remediation techniques for these soils. Initial results have shown a possible link between plant texture and lead concentration. “High surface area” edible plants include texture herbs such as mint, radish greens, and rhubarb, while “low surface area” plants include cherry tomatoes, apples, and garlic. As is indicated in the graph below, most high surface area edibles contained higher concentrations of lead in plant tissue, independent of the concentration of lead in the contaminated soil they were grown in. The sample size of plant tissues was not statistically significant, so no conclusions can be made at this time. However, this information can be useful in developing future research on the matter and providing advice to gardeners in areas with high soil lead concentrations.
The University of Maine’s Analytical Lab and Soil testing service analyzes soil for lead. You can request a soil test kit on their website. The CCSWCD and the University of Maine Cooperative Extension are great resources for information and are happy to answer any questions. Multilingual fact sheets on soil lead can be found on the CCSWCD website.
Readers who reside in one of the four high-risk neighborhoods in Portland may sign up for a free test, and can reach the District with any questions at 207.892.4700 or by email at jclark@cumberlandswcd.org.
Best Practices for Plant Sale Donors and Buyers in Maine
Developed by Tori Jackson, Extension Professor of Agriculture & Natural Resources, Lynne Holland, Community Education Assistant, University of Maine Cooperative Extension, and Naomi Jacobs, Master Gardener Volunteer
Reviewed by Katherine Garland, Horticultural Professional, University of Maine Cooperative Extension and Sarah Scally, Assistant State Horticulturist, Maine Department of Agriculture, Conservation and Forestry
What passionate gardener hasn’t slammed on the brakes at the sight of a spring plant sale by the side of the road? Sales of donated plants are a major source of income for garden clubs, land trusts, and conservation groups, as well as an exciting way for plant lovers to acquire new treasures at a modest cost.
Unfortunately, plants dug from home gardens can transmit problem organisms such as crazy worms (Amynthas agrestis), European fire ants (PDF) (Myrmica rubra), and winter moths (Operophtera brumata), as well as invasive plants like black swallowwort (Cynanchum louiseae). Several Maine plant sales have been discontinued in recent years due to such concerns. Here are steps you can take to reduce the chance of spreading invasive pests through this beloved spring tradition.
Best Practices for Donors:
Do not offer any plants the state of Maine has prohibited from being sold due to their invasive nature. Review the Invasive Plant Do Not Sell list prior to every plant sale. Similarly, many plants not listed as invasive are still troublemakers. If a plant tends to take over the garden and is hard to contain, it’s probably best not to share it with others.
Use new, sterile soil and sterilized pots to prevent transmission of seeds, disease, and insect pests, which may be present as cocoons, larvae, or adults.
Sterilize tools such as trowels and shovels. A 10% chlorine solution works well.
Before you propagate, inspect plants carefully to screen out those with any sign of pests or disease.
Pot rooted cuttings rather than divisions whenever possible.
If you do donate divisions, rinse the roots before potting, and manually remove the roots of invasive plants such as black swallowwort or bindweed. This is labor-intensive but can be effective if done thoroughly.
Work with your group to ensure that all donors follow best practices. Perhaps the group could make bulk purchases of new pots and potting soil, for instance, to reduce the cost to donors.
If you live in an area where pests are known to be established, ask your group to discuss whether the sale tradition should be suspended or discontinued.
If your inventory seems to be impacted by these pests, consider adding locally grown annual seedlings to the offering. Vegetable seedlings have been successful for some sales in this way.
Finally, the earlier the plants are dug up, divided, and potted, the less trauma the plants will experience, and the more happily they can settle into their new homes. Strong, healthy plants are more resistant to disease and less attractive to many insect pests.
Best Practices for Buyers:
If you live in an area where a pest is known to have taken hold, ask the sellers about whether their donors are required to follow best practices.
Inspect plants carefully before buying.
Rinse the roots before planting, unless you are confident that sellers have used sterile media and other best practices.
Be aware of the invasive plants prohibited for sale in the state of Maine. Some plant sales may unintentionally be offering these items, so it’s important to be an informed buyer.
Best Practices for Organizers:
Get the word out about your plant sale so that no plant remains an orphan. Social media, local newspapers, and local calendars all have deadlines that vary from a few days to several weeks before an event, so plan ahead.
An organized sales area that leads the buyers in one direction through the sale is not only efficient but also easier to manage, whether your sale is live or presale with pick-up.
For more information on the identification and control of pests mentioned above:
Crazy Worm (Amynthas agrestis)
Crazy worms are not yet widespread in Maine, but have been found in Augusta, Portland, Boothbay, and nursery settings since 2014. They damage forest habitats by gobbling up the organic layer and driving out native worms.
Winter Moth (Operophtera brumata) (PDF)
Winter Moth is found in coastal Maine from Kittery to Bar Harbor. Its cocoons are in the soil from June to November. The voracious larvae defoliate trees and shrubs.
Consider making a contribution to the Maine Master Gardener Development Fund. Your dollars will support and expand Master Gardener Volunteer community outreach across Maine.
Maine Home Garden News was created in response to a continued increase in requests for information on gardening and includes timely and seasonal tips, as well as research-based articles on all aspects of gardening. Articles are written by UMaine Extension specialists, educators, and horticulture professionals, as well as Master Gardener Volunteers from around Maine, with Katherine Garland, UMaine Extension Horticulturalist in Penobscot County, serving as editor. Special thanks to our 2020 Master Gardener Volunteer co-editors Naomi Jacobs and Abby Zelz.
Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
Call 800.287.0274 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu.
The University of Maine is an EEO/AA employer, and does not discriminate on the grounds of race, color, religion, sex, sexual orientation, transgender status, gender expression, national origin, citizenship status, age, disability, genetic information or veteran’s status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Director of Equal Opportunity, 101 North Stevens Hall, University of Maine, Orono, ME 04469-5754, 207.581.1226, TTY 711 (Maine Relay System).
Divide dahlias if you didn’t get around to that task last fall. This pictorial lesson offers helpful images and tips. Cuttings should be given approximately a week in dry room temperature conditions in order to heal over the wounds. Wait to plant dahlias until after the risk of frost has passed.
