By Elaine Mills, Extension Master Gardener
Photos by Elaine Mills
When homeowners picture gardens for pollinators (native bees, flower flies, butterflies and moths), they often think of beds of colorful flowering perennials. Trees and shrubs, the so-called woody plants, can also provide excellent support for these insects.
If you have a mature tree such as a white oak (Quercus alba), black cherry (Prunus serotina), river birch (Betula nigra), red maple (Acer rubrum), or hickory (Carya species), you are already supporting the caterpillar stage of hairstreak, duskywing, or swallowtail butterflies and the io, viceroy, and imperial moth. While most* of the adults of Lepidoptera species require nectar of flowering plants to fuel their flight, the larval stage of the insects gets nourishment from the foliage of these trees, although the signs of feeding will not be very noticeable.
On properties that only have room for understory trees, gardeners can choose from such native species as downy serviceberry, (Amelanchier arborea), eastern redbud, (Cercis canadensis), fringetree (Chionanthus virginicus), flowering dogwood (Cornus florida), or sweetbay magnolia (Magnolia virginiana). These trees in the 15- to 25-foot range can serve as “host plants” for the young of the spring azure, Henry’s elfin, and red-spotted purple butterflies as well as many moths.
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The flowers of these smaller trees also offer important early sources of nectar and pollen for bees, flies, wasps, beetles, and butterflies. These supplies are especially critical for native “specialist” bees that rely on the pollen of a limited number of plant species when establishing nests for their young. Other shorter trees that provide both floral resources and nutritious fruit for birds include pagoda dogwood (Cornus alternifolia), pawpaw (Asimina triloba), and sassafras (Sassafras albidum).
There are many lovely native shrubs that support our pollinators as well. Early-blooming species include spicebush (Lindera benzoin), black chokeberry (Aronia melanocarpa), pinxterbloom azalea (Rhododendron periclymenoides), and black haw (Viburnum prunifolium) which flower from March to April. Among the plants that bloom in May and June are wild hydrangea (Hydrangea arborescens), Virginia sweetspire (Itea virginica), and common ninebark (Physocarpus opulifolius).
The flowering of several of several shrubs is especially distinctive. Mountain laurel (Kalmia latifolia) has cup-shaped flowers with spring-loaded stamens that fling pollen onto the backs on insects visitors when tripped. Sweet pepperbush (Clethra alnifolia) is noteworthy in that it blooms in the later summer, even in shade. Witch hazel (Hamamelis virginiana) illuminates the fall landscape with its ribbon-like yellow flowers in October and November.
The full-size straight species of many native shrubs can range in height from 6 to 12 feet or more. For gardeners with very limited space, several native shrubs are also available in smaller cultivars which produce the same insect-supporting flowers. ‘Hummingbird’ is a diminutive cultivar of sweet pepperbush. The ‘Low Scape Mound’ cultivar of black chokeberry measures about 1 to 2 feet in height, perfect for use as an edging plant. Virginia sweetspire has various cultivars, such as ‘Henry’s Garnet’ (4 to 5 feet) and ‘Scentlandia’ and ‘Little Henry’ (2 to 3 feet). Whether your yard can accommodate canopy trees or only smaller shrubs, you can feel confident that your woody plants are providing sustenance to our smallest garden visitors.
*The adult stage of some moths does not feed.