Maine Home Garden News May 2025

In This Issue:

• May Is the Month to . . .
• Embracing Herbivory
• Backyard Bird of the Month: Barn Swallow
• Help Us Grow Communities and Gardens Across Maine
• Gardening in a Rental
• Book Review: Peony: The Best Varieties for Your Garden by  David C. Michener and Carol A. Adelman (Timber Press, 2017, 247 pp.)
• Maine Weather and Climate Overview

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May Is the Month to . . .

By Kate Garland, Horticulture Professional, UMaine Cooperative Extension

Divide your dahlias. If you skipped dividing dahlias* last fall, now’s your chance. Separate the tubers and let cut surfaces dry for about a week before planting directly in the garden after the last frost.

Renovate perennial beds. Lift and pot up your favorite plants, checking roots for aggressive neighboring plants. Once the desired plants are out, cover the area to suppress weeds and those persistent spreaders. Plan to replant in late August or early September, or later if needed to fully clear the space.

Prune spring-flowering shrubs. Once lilacs, forsythia, and other spring bloomers finish flowering, prune them to shape and encourage better blooms next year. Be sure to look out for nests and avoid disturbing any shrubs that have bird activity.

Enjoy spring harvests. Harvest early crops like chives, lovage, and asparagus. Freeze herbs for later and watch for asparagus beetles.

Improve soil with cover crops. Plant peas, oats, and vetch in early May, or buckwheat in late May, to boost soil health and suppress weeds.

Test before fertilizing. Get a soil test before applying fertilizer. Use slow-release nitrogen if needed, and mulch grass clippings to reduce future applications.

Mulch perennial beds. Weed, edge, and mulch your perennial beds now. Mulch conserves moisture, suppresses weeds, and improves appearance. Consider using compost as a mulch. It can be just as attractive as bark and can serve as a high-quality source of organic matter as it slowly incorporates around the root zone.

Harden off seedlings. Gradually expose indoor-grown seedlings to outdoor conditions over 7–14 days. Start by leaving them in partially shaded areas more protected from the wind. Bring them in if frost threatens.

Guard against cutworms. Use simple collars made of cardboard or plastic around young vegetable transplants to protect from cutworm damage.

Delay warm-season transplants. Wait to plant tomatoes, peppers, and cucurbits until after the last frost—usually late May or early June in Maine.

Start with cool-season crops. Now’s the time to plant hardy vegetables like kale, carrots, beets, cabbage, radish and turnip. They handle cool temps and light frost well.

Protect yourself from sun exposure. Wear a hat and use sunscreen—spring sun can be stronger than expected.

Protect berry plants. Uncover strawberries and other small fruits early this month. Cover blossoms on frosty nights to avoid damage.

Plant fruit crops. Once the soil is workable, plant strawberries, brambles, and fruit trees like apples and pears. Choose varieties suited to your site, tastes, and consumption goals.

Plant trees and shrubs correctly. Backfill planting holes with native soil to encourage strong root growth. Avoid piling mulch against trunks. Use a donut-shaped ring instead.

Try something new. Experiment with a new veggie or flower, try container gardening, or build a raised bed. Visit local garden centers for ideas and inspiration or plan on watching how the newest All America Selections perform at our two demonstration gardens, Tidewater Farm and Rogers Farm, later this season.

*No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.”

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Embracing Herbivory

By Hannah Mullally, U.S. Fish and Wildlife Service Partners for Fish and Wildlife Biologist, Maine Field Office

It happens every year. I plant out my kale seedlings, which I’ve nurtured from seed, and watch them continue to grow in the cool spring weather. Then one morning, I see someone has munched away on several leaves. Soon, I find the culprit – a small green caterpillar hiding on the underside of a leaf. These are cabbageworms, one of the many insect visitors to my garden.

Luckily, pests in the home garden aren’t usually an economic disaster. Home gardeners have wiggle room to experiment with pest prevention techniques and treatments. Home gardeners also get to set their own herbivory tolerance. Whether or not we like it, gardens are a part of the ecosystem. They are impacted by the world around it, including pests. There will always be insect pests in the garden, but beneficial visitors can also be invited into your garden. By understanding what the ecosystem has to offer, and embracing a low level of herbivory, your garden can benefit from these additional visitors.

While insect pests make a meal of plants, pest predators make a meal of the pests. To feed their growing chicks, one chickadee will forage thousands of caterpillars. Bats, too, are insectivorous, eating thousands of nocturnal insects – including the adult form of many garden pests, moths. A familiar predatory insect are lady beetles, which, as both adults and larvae, are voracious predators of aphids, mites, and scale. Predatory wasps, like yellowjackets, provision their young with insects. Parasitoid wasps, such as braconid wasps, are even more fascinating. Female braconids pierce a host caterpillar and deposit their eggs within. The braconid wasp eggs develop into larvae inside the dying caterpillar and eventually break out of the host to form cocoons. Each cocoon will develop into an adult braconid wasp. Not to be outdone, hoverflies may be the unsung heroes of the garden. In their larval form, hoverflies eat a variety of garden pests such as aphids, caterpillars, and thrips. As adults, hoverflies feed on nectar and pollen, making them excellent pollinators.

Pest predators are our allies. To keep them near the garden, we must give them a reason to visit and stay close by. Would you shop at a grocery store if there was no food on the shelves? What if a grocery store was well stocked, but was a two-hour drive from your house? Pest predators are similar. If the garden is completely void of food (i.e. living caterpillars, mites, aphids) there’s not a good reason for predators to visit. If your garden is not surrounded by or does not include their habitat, pest predators do not have homes nearby.

There are many ways to attract and maintain a healthy population of pest predators in and around your garden. The most straightforward way is to reduce or stop using insecticides in and around your garden, particularly insecticides not targeted to a specific insect pest. Indiscriminate insecticide use can directly harm beneficial insects as well as take away the food source predatory insects require. Another simple way to support pest predators is to incorporate mulch, leaf litter, standing dead plant stems, and tree stumps into your landscape. Many beneficial insects overwinter or create nests underground, in leaf litter, or within rotting wood cavities. Finally, keeping flowers blooming in and around the garden all year long will not only attract bees, but hoverflies and other predacious flies as well.

Like every year, I will continue to pick off the cabbageworms I find on my kale plants, knowing there will be many that escape my eye. But I can look forward to finding tachinid flies hovering nearby to take out the cabbageworms I miss. I may even find a munching caterpillar I choose to work around, if only for its  .

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Backyard Bird of the Month: Barn Swallow

By Maine Audubon Field Naturalist Stacia Brezinski

Barn Swallows are a graceful, long-tailed swallow, known for building nests on human structures. After migrating more than 4,500 miles from Central and South America, the swallows begin collecting mud and grass to build their cup nests. They’ll transport between 750–1450 individual mud pellets to form the base, and line the nest with grass and feathers. Understandably, reusing nests from previous breeding seasons is common, and involves replacing last year’s inner nest material (and any parasites it might be harboring), then adding new mud around the rim. Barn Swallows have likely been building nests on human structures as long as humans have been building structures. Until recently, the Anthropocene has been kind to Barn Swallow populations; these birds now nest on five continents, including traditional wintering grounds in Argentina. These South American nesters have an opposite life cycle, nesting in the Southern Hemisphere’s summer, November to February, and heading north for their winter, April to October. As insectivores, their populations are now suffering from enormous declines in insect populations (a 2019 study found that 40% percent of the world’s insect species are in danger of extinction). This reality makes their return to Maine each spring even more special. Listen for their high-pitched, bouncy chatter over fields starting in late April.

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Help Us Grow Communities and Gardens Across Maine

By Rebecca Long, Coordinator of Horticulture Training Programs, UMaine Cooperative Extension

Public and private gardens play a vital role in supporting both our health and the environment—and they thrive when backed by strong community support. Today, we invite you to invest in their future. Your donation to the Maine Master Gardener Volunteer program provides the research-based knowledge needed to grow resilient gardens and communities. It also helps train dedicated volunteers who deliver sustainable gardening education across the state.

In 2024, 655 Master Gardener Volunteers contributed 26,801 hours to educational and food security projects, reaching over 46,000 Mainers, including 5,000 youth. The Harvest for Hunger program also reached a milestone: 4 million pounds of fresh food have been donated since the program started in 2000. In 2024 alone, 258,000 pounds were distributed to food security agencies across the state.

Here are just a few of the ways Master Gardener Volunteers impacted their communities last year:

• Set up food sharing tables with culturally relevant produce
• Built wheelchair-accessible garden paths
• Stocked a free farm stand at Old Town Elementary for children and families
• Led native seed-saving workshops
• Designed and planned school gardens with students
• Gleaned excess produce for seniors and families in need
• Introduced youth to hands-on gardening at summer camp

Your donation will directly support this impactful work, helping more gardeners connect, learn, and make a difference.

Give today for Maine Day of Giving:
 http://our.umaine.edu/mastergardener

Thank you for your support!

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Gardening in a Rental

By Clarisa Diaz, Master Gardener Volunteer for Penobscot and Hancock Counties

As someone who rented apartments in New York City for over a decade, then lived in a rental home during the first years of my time in Maine, do not be discouraged by having limited space to garden. There are many ways to garden even if you can’t plant into the ground. The creativity of gardening in various alternative ways can provide a more climate-controlled environment while brightening up your home or apartment with plenty of greenery.

Window boxes, custom shelving, pots, planters, trellises, and moveable raised beds are all ways I’ve done container gardening over the years. The fun part is thinking about the spaces available to you and how you can utilize them as green spots with temporary or movable structures and containers.

Window boxes are a great and simple way to grow flowers or herbs while making your living environment green. Hanging plants can be outdoors and indoors to grow beloved plants like pothos that also help improve air quality.

If you have a balcony, patio or deck, potted plants are another simple way to add color to your environment. Change out the pots with flowers as they come into season. I have found fragrant flowers like heliotropium can last all summer long in a pot by my front porch. When the fall season rolls around I switch them out for chrysanthemums. Patio spaces can also have edible plants such as potted blueberry bushes, container herbs, and vegetables. There are various types and shapes of containers available; it is a matter of selecting those which fit your space and are suitable for the types of plants you wish to grow.

For more vegetable production, I’ve found VegTrugs, an elevated raised bed, to be great temporary raised beds. They can be constructed and deconstructed when you move to a new apartment or home. The elevated height of VegTrugs actually makes it easier to garden without bending down on your knees as you would in a traditional garden.

There are other ways to garden indoors. While not ideal, a nice south-facing window can be a great way to experiment. Add shelves in your window to make a “window garden”, a nice addition to a living room, or use vertical gardening techniques to grow plants indoors with grow lights.

Enjoy plants and gardening without having to prepare ground beds, weed constantly, and perform the additional work of removing or moving plants established in the ground—because we know that a garden evolves and changes with time. It is easier to change what you grow when nothing is set in stone or rocks! Even if you own a home or property, you may opt for gardening like you’re in a rental based on the time you have available and/or your ability to garden. Maybe some things are in the ground but other things aren’t while you figure out what you actually want to plant. Whether you’re in a rental or not, rental gardening techniques can be applied. With a curiosity to experiment and an imagination to customize your space, you can’t go wrong and will only keep learning.

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Book Review: Peony: The Best Varieties for Your Garden

By Clara Ross, Member of The Peony Society of Maine and Master Gardener Volunteer

The authors, Michener and Adelman, state their purpose in assembling the book is “to provide the information you need to grow these magnificent…” plants. Initially, the authors provide a history of peonies, which I found very interesting. They describe where peonies originated and where we may also find them growing as wild species. Although in China the peony was used for herbal/medicinal purposes and for growing as ornamentals, in the Western world breeders focused on extending the bloom season, richer colors, and stronger stems. I appreciated the description of peony anatomy or form. Tips on placement in the garden, companion plants, growing healthy plants, and disease solutions were all considered.

The authors have selected nearly 200 of what they consider to be the best peony plants for gardens and vase. The gallery of plants is organized by peony type: bush, tree, and Itoh/intersectional. In each section, the authors supply information on color, size, bloom season, support needed, and floral form (i.e. single, double, etc.), as well as any awards that particular peony has won.

In addition, I found a variety of resources, such as where to purchase peony plants or cut blooms, public gardens which have peony displays, U.S. hardiness zones, books for further reading, and an index. There were many photos of peonies in gardens (I imagine most of them were Adelman’s own), but few noted what garden the photo was taken in! That surprised me. The most helpful part for me were the suggestions for peony complements. I will definitely use those ideas.

The co-author of this book, Carol Adelman, founder of the famed Adelman Peony Garden, will be the keynote speaker at the 25th anniversary celebration of the Peony Society of Maine to be held on June 21, 2025. Along with Adelman, we will also be enjoying an elegant afternoon Victorian Tea Party. The event will be held from 1:00 to 4:00 PM at Buchanan Alumni House, 160 College Avenue in Orono.  Non-members are welcome to join. Tickets must be purchased ahead by sending $40.00 to: The Peony Society of Maine, P.O. Box 2498, Bangor, ME 04402. If you need more information, please contact Lynn Anderson: secretary@peonysocietyofmaine.net.  

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Maine Climate and Weather Update

By Sean Birkel, Assistant Extension Professor, Maine State Climatologist, Climate Change Institute, Cooperative Extension University of Maine

NOAA statewide summaries, released since the last newsletter, rank March 2025 as 18th warmest (top 1/3) and 26th wettest (top 1/3) for data beginning 1895.  From late March through the end of April, daily station observations from Bangor, Caribou, and Portland show that diurnal temperatures have been near to slightly above normal (about 60th percentile for April mean), producing lake ice-out and spring phenology this year close to the historical norm.  April precipitation through the 28th is above normal at Bangor and Caribou, ranking 9th wettest [88th percentile] and 11th wettest [87th percentile], respectively, and slightly above normal at Portland, ranking 39th wettest [54th percentile].  Streamflow and groundwater hydrologic indicators are in the normal range for this time of year across most of the state, except across parts of Androscoggin, Cumberland, Sagadahoc, and York counties where abnormal dryness or moderate drought persists from lingering precipitation deficits.

The latest 10-day weather forecast (morning April 29) shows a seasonable start for May with near to above normal temperatures and potential rainfall.  A cold wave could developed bringing frost or freeze on the 5th or 6th.  The probabilistic climate outlook for the month of May (see table below) shows a lean toward warmer than normal temperature and below normal precipitation.  The May–July seasonal outlook predicts above normal temperature and equal chances of above or below normal precipitation.  As always, visit weather.gov for the latest weather forecast for your area. For additional information, including historical temperature and precipitation data and weather forecast maps, visit the Maine Climate Office website.