We hear a lot about supporting pollinators in mainstream publications, but it is often difficult to find information that provides thorough lists of plants (not just the top 5 flowers), includes both larval food and nectar plants, includes bats and beetles rather than just bees and butterflies, or is specific to the regions in which we work. This is a great resource from the Pollinator Partnership on choosing Plants for Pollinators in our ecoregion here in the northeast. Does it include all the plants that support pollinators in our region? No. But it is a great place to start!
As pollinator habitat disappears, through development of native habitats, pesticide use, and other stresses, there has been a large body of research and instruction on how to support pollinators (and other beneficial insects) with native plants and overwintering techniques. Many sites recommend leaving dead plant material through the winter to help pollinators and other insects overwinter, and removing it in spring. Yet, spring happens over an extended period of time, weather warms and cools repeatedly, plants bloom early one year and other years, so I find the term “spring” to be rather vague.
Are there indicators we can use as guidelines for ecological garden maintenance? I found it difficult to find practical information about when it is relatively safe to remove overwintered debris in spring, but these sources about native bees that I’m sharing here provide a lot of information that can guide our recommendations and practice.
Bulletin #715 from the University of Maine Understanding Native Bees states, “The most likely place to find bees is in the flowers of native plants, when the day is sunny, relatively calm, and the temperature is above 70°F. To be active, fly and feed, bees need to be warm. A few species are active below 60°, but most prefer temperatures above 72°.” And, “Although some species may be active by late February if temperatures are unusually warm, the vernal bee species (those present in the spring) generally become active by mid-April. You may observe them on early blooming flowers, such as willow catkins and dandelions. Some native bee species continue their activities into the autumn until the last asters, dandelions and autumn dandelions die.”
“A suitable habitat for any bee species must contain a minimum of productive floral resources and patches, as well as nesting sites, and each of these must be within flight range of each other. While bees can often exploit many different floral resources, solitary bees often have specific species that they utilize for their pollen sources. If these bees require specific pollen sources, their life cycle will often revolve around the blooming period of the specific plants. The adult bees will emerge when the plants are in bloom, so that they are able to maximize pollen collection (Cane, 2001) UVic Restoration Project. For instance, the blue orchard Mason bee nests in stems or manmade nesting tubes and their emergence coincides with the blossoming of most fruit trees, including apples, pears, and stone fruits (Home Orchard Society).
Despite being from California, the general guidelines from entomologist Robbin Thorp should be applicable elsewhere: “It’s probably best to frame the bee calendar in context of the bloom of various plants,” Thorp points out. “Manzanita (a CA native) is one of the first flowering shrubs and when they come in to bloom that is the time to look for queens of our two early bumble bee species, Bombus melanopygus and B. vosnesenskii. Some of our large digger bees like Habropoda and some Anthophora come on during that bloom. In the vernal pools, early flowering starts in late February and some of our solitary ground nesting mining bees, Andrena start about then. When the red bud comes into bloom about mid-March the Blue Orchard Bee (BOB), some othe
r species of bumble bees, and some sweat bees come out. Leafcutting bees (Megachile) and some long-horned digger bees (Melissodes and Svastra) start their activity about mid-May. ”
And another great resource is Heather Holme’s website Restoring the Landscape with Native Plants. The website provides very
accessible information on a wide variety of plants and insects native to the Midwest (many that the Northeast has in common) and discusses how the plants and insects interact with each other. The website for her book Pollinators of Native Plants includes links to downloadable full-color pdfs of native plants for specific site conditions, the nesting habits of native bees, and common host plants of butterflies, skippers, and moths.
And for those on the West coast:
Below are some helpful online resources showing what native plant species benefit what birds, mostly as food sources, but some as cover or nesting material. Adding a variety of these plants to your landscape can support bird ecology with cover protection, nesting material, fruit and seeds for multiple seasons, and increasing the insect population that many birds feed upon. These plants also support pollinators, such as bees and butterflies, and other beneficial insects. Native plants can easily fit into a traditional landscape while adding beauty, drought resistance, and increased biodiversity for a variety of ecological benefits.
Native Plants for Breeding Birds by Credit Valley Conservation is a beautiful visual reference that includes foraging guilds and nesting.
Gardening for Wildlife Plant List.pdf by Loudoun Wildlife Conservancy. This list includes wildflowers, shrubs, and trees. The document also provides a great list of books used to develop their plant list and which provide even more detailed information.
Audubon now has a Native Plant Database that allows you to enter your zip code to search the native plants in your area and includes information about which bird species those plants support – this one is pictorial and lists plants alphabetically. Or you can use the Full Results page that provides the information as text. Both tabs allow you to search and filter by plant type, plant resources (think fruit, butterflies, seed) and attractors of specific bird families (hummingbirds, finches, warblers, etc.).
Winter often seems like an “off” season for the garden. There are no blooms, no butterflies, and many of the birds have flown south. But for those of us who live in a temperate climate, there are still a lot of things happening in the landscape.
For one, the cold is an important part of a plant’s life cycle. Dormancy allows a plant to save energy for the following season’s growth. It allows the plant to weather below-freezing temperatures without damage. Cold is required for many seeds to germinate.
Snow introduces small amounts of nitrogen into the soil. Snow insulates the ground, keeping it frozen, and helping to prevent frost heave. It also helps plants from sprouting too soon during un-seasonally warm weather. Microbial activity also continues at low temperatures. These microbes are important because they help break down soil nutrients to a form that plants can use. Plants don’t directly “eat” the soil, instead they have a symbiotic relationship with the soil microbes that help them utilize the nutrients. If you have happy, healthy soil, your soil microbes will still be busy during the winter.
Any remaining foliage, dead leaves, and coniferous trees and shrubs can provide a multitude of insects, birds, and animals with protection or food.
Ecological Landscaping Techniques
Many people advocate removing dead plant matter from the landscape in the fall. Although there is a chance of voles using leaf litter as protection and causing damage, there are many reasons. Learn which plants to remove leaf litter from and which can remain. Fruit trees and roses benefit from removing debris which can harbor fungal disease or pests from the ground under them. Elsewhere in the garden, this leaf litter serves many important functions. Read the pamphlet for a more detailed discussion: Life in the Leaf Litter (1.7 MB pdf)
Remember that keeping raw materials on-site is efficient and sustainable. It returns nutrients in your garden back to the soil and it decreases your town’s cost and fuel requirements for landscape waste removal and processing.
Plant Choices
Native plants often provide many more ecological benefits than introduced species, including cultivars. For instance, Rutgers hybrid dogwoods, a cross between kousa and native dogwoods, are sterile (meaning they do not produce seeds that will produce more plants) and the cultivar is more resistant to insects and disease. Also, the berries of the some plant cultivars, like ‘Winter Sprite’ winterberry, are not eaten as readily by birds as the native winterberry. If you mourn the fact that the berries of a plant are eaten by birds too quickly and you can’t enjoy the red color throughout winter, consider planting both a native and a cultivar. That way, you will not deprive the birds of an important winter food source. Your plant choices have an impact on other things beside the designed space, so if you are trying to have a sustainable or ecologically-friendly landscape, read about the plants you are considering or consult reliable sources like the New England Wildflower Society.
Ice Covered Grasses
Remember that some berry producing plants, like hollies, are dioecious and require both a male and female plant in order for the female to produce fruit. It is also important to plant species that are appropriate for the site based on the plant’s requirements for moisture, soil type, heat, cold, and light.
Natural Architecture
Another thing that I enjoy about plants in winter is that they provide striking architecture in the winter garden. This is one of the reasons that I don’t remove dead plants until spring. It isn’t just the coniferous trees and shrubs – I enjoy seeing the snow and ice on most of my plants.
I hope that despite the overwhelming amount of snow this season, you can find beauty in the important ways that the snow and cold weather provide valuable ecological services to our environment. Grab your snowshoes and go look for something unexpected!