Spring Wildflowers

A window of light

In April, before the maples and basswoods leaf out, the floor of a Wisconsin hardwood forest gets full sun. Within a few weeks the canopy closes and the floor goes dim for the rest of the year. A group of wildflowers called spring ephemerals lives in that gap: they come up as the ground thaws, flower, and make their food while the light lasts, then go dormant as the canopy fills in ¹. Most are perennials that store the season’s food in bulbs, corms, or roots for next year’s growth ¹. By midsummer you’d never know they were there.

The ones to know

Walk a rich woods from early April into May, especially north-facing slopes and ravines in the Driftless and the maple woods of the north and east, and they come roughly in order:

• Hepatica comes first, small lavender, pink, or white flowers on fuzzy stems, with last year’s leathery three-lobed leaves still lying on the litter.
• Bloodroot: one white flower with a gold center, wrapped in a single lobed leaf as it comes up. It blooms before the leaf unfolds, and its petals drop within a day or two of pollination ², so you have to catch it. The leaf keeps growing after the flower fades, up to 9 inches across ². Snap a root and it bleeds orange-red sap.
• Dutchman’s breeches: white flowers shaped like pairs of pantaloons hung upside down. Its nectar sits deep in the spurs, where only the long tongues of early-flying queen bumblebees can reach ³.
• Trout lily: a nodding yellow flower with petals swept back, over mottled leaves that look like the side of a brook trout ⁴. A flowering plant has two leaves and one flower ⁴; a carpet of single leaves with no flowers is young plants not yet old enough to bloom. On UW–Madison’s Muir Woods hillside, trout lily and toothwort are the most common ephemerals ⁴.
• Spring beauty: small white-to-pink striped flowers that open only in full sun and close when a cloud comes over ¹.
• Large-flowered trillium: a big white flower of three petals over three leaves, turning pink as it ages, later in the season as the canopy starts to fill.

Pollinators in a cold month

Flowering in April means flowering when few insects are flying. Many ephemerals depend on native bees, especially early queen bumblebees and small solitary bees, and on flies ¹. In return they’re some of the first food of the year for those insects, and their roots hold the soil while little else is growing ¹. Bloodroot hedges its bet: bees and other insects cross-pollinate it, but if none come it can pollinate itself ².

Ants plant the seeds

Look closely at a ripe bloodroot or trillium seed and you’ll see a pale, fleshy bump attached to it: an elaiosome, rich in fats and proteins ¹. Ants find the seeds, carry them home, and eat the elaiosome. Then they haul the seed out to their refuse pile, where it’s protected and sits in rich soil until it germinates ². Nearly all the spring ephemerals use ants this way; it’s called myrmecochory ¹. It’s also why ephemerals spread slowly: an ant only carries a seed a short distance, so a colony of bloodroot or trillium creeps outward over decades. Bloodroot grown from seed takes 2 or 3 years to flower ².

What’s thinning them

Two things have changed Wisconsin’s woods since these flowers had them to themselves.

Deer. UW–Madison botanist Don Waller’s team revisited 62 forest sites in northern Wisconsin and Michigan first surveyed in the 1950s and compared plants inside and outside fenced deer exclosures. Outside the fences, trillium, orchids, and lobelias had declined while grasses, sedges, ferns, and weedy plants deer don’t eat had increased. They traced at least 40 percent of the region’s 60 years of understory change directly to deer ⁵. A woods carpeted with trillium in May is a sign that deer there are kept in balance.

Garlic mustard. This invasive biennial makes a rosette of scalloped, kidney-shaped leaves its first year and flowers with small white four-petaled flowers the second; crushed, it smells of garlic ⁶. It moves into high-quality woods and releases chemicals that disrupt the mycorrhizal fungi native plants rely on, and native wildflower cover drops where it spreads ⁶. Its seeds last at least seven years in the soil, so control means pulling it every spring before it sets seed, bagging any that are flowering ⁶. Don’t pull native toothwort or sweet cicely by mistake: both bloom white at the same time ⁶.

And don’t dig wild plants for a garden: over-collecting has caused big declines in bloodroot and others ². Buy nursery-propagated plants instead.

What to take from this

Spring ephemerals live in the few weeks between thaw and canopy closure, storing food underground and vanishing by summer. Learn hepatica, bloodroot (one-day flowers), Dutchman’s breeches (queen bumblebees), trout lily (mottled leaves, two leaves per flowering plant), spring beauty, and trillium. Ants plant their seeds for the oily elaiosome, so colonies spread slowly. Deer browse and garlic mustard are what’s thinning them: pull garlic mustard in spring, and read a trillium carpet as a sign deer are in balance.