In April our gardens come to life. As mud, rain showers, thawing, and drying permit, it’s time for trimming, planting, spring monitoring, and weeding. Plant bare root stock or potted dormant or semi-dormant trees and shrubs this month, prior to the spring flush of growth. In the native plant garden we are trimming beds in areas that will not be managed with prescribed fire this year. Early season weeds that greened up in March are ready for digging now before they flower and set seed. We are also enjoying working outside, observing seasonal changes.
Spring patterns of native plant growth become apparent this month. Some species have leaves that overwinter in a rosette form. A rosette is a very short stem that holds its leaves close to the ground—dandelion (Taraxacum officinale) is a familiar example. Prairie-smoke (Geum triflorum), golden alexanders (Zizia spp.), and wild columbine (Aquilegia canadensis) are spring flowering species with this pattern. Each season, additional new leaves grow, the stem and/or flower stalks extend, and blooming and seed set are complete by mid-summer. This pattern holds for many (weedy) members of the mustard family, one reason for urgency in removing them before their rapid blooming and seed set.
In another group, leaves emerge and expand before the flowers form. Jacob’s-ladder (Polemonium reptans) compound leaves appear early, tinged with reddish pigment. Later, the leaves are green and pale blue flower clusters extend, rising from the center of the rosette. In wild ginger (Asarum canadense) the leaves are folded in half as they emerge from buds on shallow rhizomes, right at the soil surface. The unusual three-parted deep red flowers bloom shortly after this, hidden under the leaves. Trout-lily (Erythronium spp.) has mottled leaves and spreads in the garden, like wild ginger, by vegetative growth. When it blooms, the pendulous flowers are held singly above the leaves.
Some spring-blooming species bear flowers before leaves. Leatherwood (Dirca palustris), a shrub of mesic woodlands, has pendulous yellow flowers that last only a few days. As they bloom, the leaves emerge in clusters. Oaks (Quercus spp.), hazelnut (Corylus americana), and ironwood (Ostrya virginiana), have inconspicuous flowers and are wind-pollinated. American plum (Prunus americana), with showy white fragrant flowers, is insect-pollinated.
For more information about both native and weedy species that bloom this month, see the WisFlora April wildflowers page.
You’ll find plants for any garden setting at the Friends of the Arboretum Native Plant Sale under the big tents on May 13, 9 a.m.–2 p.m. FOA also provides information sheets and expert advice at the sale. Please mark your gardening calendar and see you there!
—Susan Carpenter, Arboretum Native Plant Gardener