Why plant a pollinator garden

Maritta Perry Grau
Frederick County Master Gardener

(7/1) Imagine you are sitting outside on a warm summer morning with a cool drink and a muffin made with blueberries from your own bushes. You look out over a garden filled with brightly colored flowers and butterflies that flit from blossom to blossom. Listening closely, you hear the low drone of dozens of bees enjoying the blooms. Birds chirp in the shady oak tree above you. You laugh at the antics of a chickadee hunting caterpillars for its hatchlings.

Now imagine the alternative. You are inside, looking out over a boring expanse of green lawn. Nothing stirs. There are no insects because there are no flowers, no birds because there are no insects.

Your garden and its plants can have a positive impact on the environment, supporting the foundation of the food web that sustains all life. More than 95 percent of bird species, as well as fish, reptiles, amphibians and mammals, depend on insects as a source of nutrition, according to Dr. Karin Burghardt, assistant professor in the Department of Entomology at the University of Maryland, in a recent lecture to the Frederick County Master Gardeners. It is no accident that the dramatic decline in insect populations closely correlates with the decline in many bird species. We can help slow or halt the decline of pollinators by establishing pollinator-friendly gardens in our own environs.

Insects are critical to our food supply. Insects pollinate many important crops, such as melons, squash, apples and stone fruits. The plants will flower, but if the flowers are not pollinated there will be no production. This applies to the crops you grow in your backyard garden as well as those grown by farmers—the produce we buy every day at the market. Fewer pollinators mean fewer fruits and vegetables, which in turn means higher costs when we shop.

Creating a garden that supports pollinating insects starts by focusing on native plants. Studies have shown that gardens containing native plants support many more insects and a more diverse insect and bird population than gardens containing only non-natives. Because native plants co-evolved with native insects, they are the ideal source of the nectar, pollen and vegetative parts that serve as food for these insects.

Another reason that you might want to use native plants is that once such a garden is established, it requires no pesticides or fertilizer, little or no supplemental water, and relatively little maintenance. Since these plants evolved in our area, they are well adapted to our soils, summer heat and humidity, and late summer droughts.

This doesn't mean that you cannot grow the peony from Grandma’s garden. Research has shown that yards with up to 30 percent nonnative plant biomass (trees, shrubs, flowers, vegetables and grass) will still support a healthy population of diverse insects.

When selecting plants, consider the bloom period, as well as flower shape, size, and even color, of each species you plant. There should be flowers blooming from early spring through late fall. While some insects utilize flower nectar, many others have specialized mouthparts that best fit only certain flower shapes. Long-tongued insects reach deep into tubular flowers such as honeysuckle or bee balm, while short-tongued insects prefer shallow flowers such as asters and goldenrod. Bees prefer flowers that are purple, blue, yellow or white. Butterflies are attracted to yellow, orange, pink and purple blossoms. Some flowers have "nectar guides," stripes that direct an insect into the nectar-rich portion of the bloom. Be sure to include trees, shrubs, perennials of different heights, and groundcovers–each level plays an important role in providing insects with shelter, nesting sites and cover from predators.

Finally, when you design your pollinator-friendly garden, make sure you provide appropriate water sources; offer year-round shelter for insects, birds, and other animals; and create an environment free from poisons, invasive plants, and other hazards.

Now we’d like to take a look at the elements essential to a successful pollinator garden: appropriate food sources, water, year-round shelter, and an environment that is free from poisons, invasive plants, and other hazards.

Food

Flowers should bloom in your garden from early spring through late fall, especially since food is critical during these early and late seasons. You can supplement native perennials with annuals such as Mexican sunflowers (Tithonia) and zinnias. A list of Maryland native plants is available at https://extension.umd.edu/resource/recommended-native-plants-maryland.

Be sure to include some plants that will serve as host plants for butterfly and moth larvae, such as those listed at https://dnr.maryland.gov/wildlife/pages/habitat/wahumbutbee.aspx. If you don't encourage butterflies to breed in your garden, you will likely see fewer adult butterflies. Monarchs, by the way, lay eggs only on milkweed plants.

Once you have selected your plants, cluster multiples of each plant type. Insects are selective feeders and prefer to forage from one species at a time. They expend considerable energy if they have to travel very far to reach similar plants. It is therefore recommended that a garden contain at least five plants or three square feet of each species.

Water

Water is essential for life. This is true of insects just as it is of humans. Although insects may obtain water from raindrops or dew, these are often not available during stretches of hot dry weather. A shallow pie pan containing a layer of stones and filled with water allows parched insects to perch safely while drinking. Refresh the water daily to prevent mosquitoes from breeding.

Some butterflies will gather in muddy areas to drink water and extract minerals from damp soil. This behavior, know as puddling, can be encouraged by placing a shallow pan of moist sand in the soil of your garden. Make sure to keep the sand moist.

Shelter

Insects require shelter throughout the year. Depending on the species, the ideal shelter may be soil, fallen leaves, plant stems or dead tree branches. About 70 percent of native bees are ground nesters. Leaving bare patches of soil throughout the garden will make it easier for these essential insects to reproduce. Instead of thick layers of wood mulch, plant short, spreading, perennial groundcovers between your larger garden plants. Like wood mulch, these plants will help conserve soil moisture and block out weeds. They will also provide a natural space where insects can find shelter, flowers on which to feed, and host plants for their larvae.

In the fall, go easy on garden cleanup. Allow leaves to remain where they fall (mulch them into the lawn with a mower), or rake them into the flowerbeds. Many insects use hollow stems, such as those produced by goldenrod and Joe Pye weed, to overwinter their young. Many butterflies and moths overwinter in fallen leaves. Fireflies lay their eggs on the soil, and the nymphs live in leaf litter and eat unwelcome slugs for over a year before becoming adults.

Fallen branches or sections of logs also make an excellent shelter. As the bark loosens, some insects burrow under the bark layer to lay eggs and to shelter over the winter.

Safe Habitat

Avoid using insecticides in or near your pollinator garden. These are toxic compounds that are intended to kill insects. Reduce or eliminate the use of fertilizer by selecting plants, especially natives, that are adapted to your garden conditions. Any chemicals added to the garden may have unintended consequences.

Remove invasive plants such as garlic mustard, Asian bush honeysuckle and butterfly bush. Although attractive to insects, these plants provide little or no nutrition and can quickly take over your garden.

Finally, avoid garden practices that may harm delicate insects and fragile baby birds. Bug zappers kill many more beneficial insects than harmful ones. The outflow from a leaf blower may reach a speed of over 150 mph, which can blow insect eggs and larvae off the plants. Bright outdoor yard lights disrupt the behavior of moths, fireflies, and other night creatures, and may disturb nesting birds.

Many resources are available to help you design and maintain a pollinator garden. Check our sidebar for Web URLs. Your local Frederick County Master Gardeners are always available to help with specific questions. Visit www.extension.umd.edu/frederick-county/home-gardening, or call us at 301-600-1596.