In Marjorie’s Garden, USDA Zone 5, and along the lane that connects us with the highway, three native plants that attract beneficial insects begin to flower in mid-July. For New England gardeners in Zones 6 and 7, these same plants began blooming in early July and late June, respectively, and gardeners in Zones 4 will start to see them flowering around the end of July. (All of this is not as precise as it sounds, of course, but, as Robert Frost reminds us, “There are roughly zones whose laws must be obeyed.”)
Lucky is the gardener who can consider these summer-flowering native plants as part of the garden insectary, that extension of the garden that keeps beneficial insects nearby through the growing season, providing them with essential nectar and pollen. Such plants ensure the presence of bumble bees, solitary bees, and other essential pollinators for the vegetable garden crops. Adult hoverflies and ladybird beetles, insects whose larvae have an insatiable appetite for aphids and whiteflies, also depend on the pollen and nectar of insectary plants for their survival.
We’ve not had to work very hard in creating the insectary in Marjorie’s Garden. The best insectary plants turn out to be those species that grow along the edges of the lane, at the curve in the lane as it enters our driveway, and in any sunny spot left natural.
There are two native species of Spiraea that have been largely passed over as garden worthy in modern times, seldom seen in nurseries or garden centers. Both meadowsweet (S. alba var. latifolia) and steeplebush (S. tomentosa), also known as hardhack by haymakers for its hard, brittle stems, are in bloom from mid-July through August, but it is the meadowsweet that functions as a magnet for insects.
The small pink or white flowers of meadowsweet, borne in terminal branched clusters, become a conspicuous summer feature of New England meadows, pastures, and roadsides. In autumn you can recognize it by leaves turned to tarnished gold, and in winter by the pale brown to red-brown seed heads that float shadows on the blanket of snow.
In a comprehensive study of native plants conducted by Michigan State University, meadowsweet was the third most attractive plant to beneficial predator insects and spiders, over four times as effective in attracting predators as a grass control. Beneficials attracted by meadowsweet included both crab and jumping spiders; soldier beetles that eat aphids and other insects; plant bugs that prey on leaf beetles; damsel bugs that prey on aphids, leafhoppers, mites, and caterpillars; lady beetles important in controlling aphid populations; and ichneumonid wasps, parasitic wasps that prey on beetles and caterpillars. In the same study, meadowsweet attracted moderate numbers of bees, including bumblebees, sweat bees, and Andrenid bees, all very common pollinators in Maine.
Mid-July begins a parade of flowering goldenrod species in and around Marjorie’s Garden, a display that lasts until late September. Along the dry edges of the lane it starts with the flat-topped flower clusters of Solidago juncea, early goldenrod, its bright yellow flowers opening in dense, plume-like panicles on the ends of stiff, narrow-leaved stems that grow three feet tall.
Beneficial insects that rely on goldenrod nectar and pollen include butterflies, native bees, hoverflies, and predator wasps, such as the great black wasp, a species that derives its own nourishment from nectar but captures plant-munching grasshoppers, cicadas, katydids and related insects to feed its young.
A few of New England’s native goldenrod have become commercially available, including one of my favorites, the elm-leaved goldenrod (Solidago ulmifolia) which comes into flower in late August. It grows up to four feet tall with terminal clusters of yellow flowers borne on short outward-arching stems. A plant in flower looks like a fireworks display.
Queen Anne’s Lace
Mid-July also brings the flowering of the wild carrot, Queen Anne’s Lace (Daucus carota), all along the lane, up the drive, and into the garden proper. This ancestor of the garden carrot has gracefully inserted itself into the flora of New England without competing with native species for resources. It has become naturalized and should not be considered invasive.
Queen Anne’s Lace is a biennial (just like a garden carrot allowed to remain in the ground a second year) with 3-inch-wide clusters of flowers, called umbels, each borne 2- to 3-feet high on stems with ferny foliage. Before opening, the umbels are claret-colored or pale pink, turning bright white and rounded in full bloom. As the flowers give way to seeds, the umbels contract and become concave, resembling birds’ nests. Dried seedheads eventually abscise, becoming tumbleweeds on autumn winds.
On sunny afternoons in July and August, I find wild carrot flowers covered with lacewings (whose larvae eat aphids and mites), ladybugs, hoverflies, parasitic wasps, and bees, both bumble bees and solitary bees.
Not every insect attracted to meadowsweet, goldenrod, or Queen Anne’s lace (or any other plant in the insectary) is a pollinator or beneficial predator species. For example, in and around our garden, meadowsweet attracts several species of “flower beetles”, insects that feed on pollen, stamens, and nectar. So far this summer, I have found three different species of these beetles crawling over flower clusters of both meadowsweet and Queen Anne’s lace and I recall from previous years that goldenrods also attract their share of these beetles.
All three of these summer-flowering plants also attract spiders, many of which are indiscriminate predators, hiding in wait within the flowers to capture visiting bees, beetles, butterflies, or other insect. My favorite among these bandits are the crab spiders, beautiful creatures that are able to capture prey several times their own size. Through this past week I kept tabs on a yellow crab spider that took up residence among a cluster of pink meadowsweet flowers. One morning it had its legs wrapped around a doomed Japanese beetle. The following morning it was still there, motionless, waiting for its next meal to crawl near, another beetle or perhaps a bumblebee. Crap spiders seem to be indiscriminate about their prey, taking whatever invertebrate that comes their way, herbivore or pollinator.
Such is the nature of the garden food web. It is not always functioning in the gardener’s best interest, but then the gardener, like the meadowsweet plant, flower beetle, or crab spider, is but one strand of the web.