What Are Spring Ephemerals?

In early spring, the understory of this deciduous woodland is bright with the flowers of false rue anemone (Enemion biternatum) and other spring ephemerals.

Spring ephemerals are herbaceous (non-woody) plants that emerge, flower, set seed and die back in spring. Many are woodland plants that take advantage of the brighter sunlight and more abundant moisture early in the season, before trees are fully leafed out.

These plants are an important source of nectar and pollen for insects that also emerge in early spring. The insects, in turn, are important pollinators for these plants. Ephemerals depend on them to fertilize their flowers so they can develop seeds. 

Because spring can be fickle, though, some ephemerals can also self-pollinate. If it's too cold for insects to fly, for example, several species can fertilize themselves. The resulting seeds carry the same genes as their parent, so the plants that grow from them are clones of that parent.

Vegetative reproduction also helps the plants spread. The false rue anemone pictured above, for example, produces not only seeds but also tuberous roots that can grow new plants. The large colony in the photograph is largely created in this way.

Most if not all spring ephemerals are perennials. After the plants flower and release seeds, the leaves of true ephemerals die back to bulbs, rhizomes, or other underground parts that store energy for next spring's growth. Some early-flowering plants keep their leaves for much of the growing season. Although these plants aren't true ephemerals, they are often included in that group.

Two Common Ephemerals

Dutchman's Breeches (Dicentra cucullaria)

Dutchman's breeches flower in April or May in the understory of deciduous forests. True to its name, its flowers resemble breeches (or britches) hanging upside down on a clothesline. 

Left to right: Dutchman's breeches flowering in early April; seed capsules ripening in mid-May; leaves gone by late May, leaving only light red tuber-like structures that store energy for next season's growth. 

The flowers are pollinated primarily by bumblebees and honey bees (1), but they can self-pollinate if the bees are absent. Seeds produced by self-fertilization may not be viable, however, and some consider the plants to be obligate out-crossers, meaning they form viable seeds only by out-crossing (2). After flowering, the plants develop elongated capsules containing dark, roundish seeds that are dropped from the capsules and distributed by ants (3). (See also Antsy Plants, a post about seed dispersal by ants.)

After flowering and seed formation, the leaves of Dutchman's breeches quickly decline. By late spring  only small, reddish bulbs or tubers remain. These storage organs are dormant until fall, when they develop leaf primordia (embryonic leaves) and flower buds. The primordia and buds then are dormant until spring, when they give rise to leaves and flowers (4). 

Bloodroot (Sanguinaria canadensis)

Another early spring bloomer, bloodroot is named for the red sap that fills its roots, flower stalks and leaf stalks. It emerges a little earlier than Dutchman's breeches, but the two overlap in their flowering time. Bloodroot is pollinated primarily by mining bees, but also by cuckoo bees, bee flies and sweat bees (5). 

Left to right: Bloodroot flowering in mid-April; elongated capsules maturing in mid-May; brown seeds with white elaiosomes in early June. 

Initially, bloodroot leaves are wrapped around flower stalks like cloaks, but eventually they unfurl, flatten and expand. Unlike Dutchman's breeches, bloodroot leaves persist until late summer before they die back..

In early to mid summer, bloodroot flowers are replaced by elongated capsules full of ant-dispersed seeds. Like Dutchman's breeches, bloodroot seeds have attached elaiosomes (eh-LAY-oh-sohms, literally "fat bodies"), They look like tiny worms, but these plant tissues are full of protein and fat that entice ants to carry the seeds to their nest, detach the elaiosomes to feed to their larvae and leave the seeds to germinate in a presumably safer place. 

Where to Find Spring Ephemerals

Wherever there are native deciduous forests, there should be spring ephemerals. Visit Scientific and Natural Areas and state and regional parks, such as Nerstrand Big Woods State Park in southeast Minnesota, Elm Creek Park Reserve in Maple Grove, or Mille Lacs Kathio State Park near Onamia. 

White trout lily (Erythronium albidum) flowering near Mille Lacs Kathio State Park in late April.

There are many more places to enjoy spring ephemerals. To find them, visit iNaturalist and look up the species described above (or others), or use the Minnesota Natural Resource Atlas. To use the atlas, open the Mapping Tool, choose Add Layers from the Options menu box, and in the Biota category choose Native Plant Communities -- Parks & Trails. Zoom in and look for areas of Mesic Hardwood Forest System.

Wisconsin and Iowa are also good places to look for spring ephemerals. A quick search finds that, in Wisconsin, the Northwoods Wildlife Center near Minocqua and Rib Mountain State Park near Rib Mountain are full of spring ephemerals. The Iowa DNR has a webpage dedicated to Woodland Wildflowers & Reports. The listed sites are from 2025, but the same should be true for 2026. 

References

1. The pollination ecology of Dicentra cucullaria. Lazarus Walter Macior, American Journal of Botany, Vol. 57, No. 1. 1970. 

2. Flowering ecology of some spring woodland herbs. Douglas W. Schemske and others. Ecology, Vol. 59, No. 2. 1978.

3. Myrmecochory: How Ants Shape Plant Communities. Julie Michaelson, Xerces Society. 2024. 

4. Dicentra cucullaria. Flora of North America, Vol. 3. Website accessed 2-17-26.

5. Pollinators of Native Plants: Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants. Heather Holm. Pollination Press, LLC. 2014. Available here and at some libraries.

Can Red Elderberry Outcompete Common Buckthorn?

Red elderberry, Sambucus racemosa, breaks it buds in early spring. Its phenology makes it a potential
competitor with common buckthorn, Rhamnus cathartica. 

One of the frustrations of removing common buckthorn (Rhamnus cathartica), is that it keeps coming back. Cut stems that aren’t treated with herbicide will sprout multiple shoots, and in areas where buckthorn has been removed, more sunlight is available to support the growth of sprouts and seedlings.

Controlling buckthorn then requires repeated visits to cut, re-treat or pull up the plants. Buckthorn seeds remain viable in the soil for up to five years, so several trips are necessary to remove seedlings and young plants. Even after the buckthorn seed bank is exhausted, nearby stands provide additional sources. Birds that eat the fruits can drop seeds into the treated area, turning buckthorn control into an ongoing project.

Buckthorn seedlings thrive where higher light intensity reaches the
forest floor.

Recognizing these challenges, scientists at the University of Minnesota are looking at a new way to manage this invasive plant. Instead of investigating mechanical or chemical controls, their research, called the Cover It Up study, asks whether native plants can thwart recolonization by exploiting buckthorn’s weakness: shade intolerance.

One of the plants in their study is red elderberry (Sambucus racemosa), a common understory shrub. Contrary to the perception that buckthorn leafs out earlier and retains leaves later than any native plant, elderberry is one of the earliest plants to resume growth in spring – even earlier than buckthorn. It also holds its leaves well into fall, rivaling buckthorn as the understory plant with the latest senescence.

That extended phenology suggests that both buckthorn and red elderberry are shade-avoidant, not shade tolerant. In fact, co-principal investigator Michael Schuster and his colleagues found that buckthorn growth is linked to light availability in spring and fall, but not in summer (1). Schuster and others also think that forests with a diverse understory can better resist invasion, because species with extended phenologies, like red elderberry, can block light from reaching buckthorn during those critical seasons (2).

Phase 2 of the Cover It Up study began in 2020. This expanded part of the research enrolled citizen scientists across Minnesota to remove buckthorn, establish experimental plots and sow seeds of native grasses, sedges, wildflowers, shrubs and trees. Their aim is to see what techniques can best prevent buckthorn recolonization in different parts of the state.

Phase 2 will conclude this year, and although it’s closed to new volunteers, anyone interested in following the research can subscribe to the quarterly project newsletter.

For more information about the Cover It Up study, including a list of species included in the Phase 2 seed mix, visit the project website at https://coveritup.umn.edu/. The seed list is under the Resources tab.

To learn how to identify buckthorn and how it harms ecosystems, visit these sites:

University of Minnesota Extension Service
Minnesota DNR
Minnesota Department of Agriculture
Woody Invasives of the Great Lakes Collaborative

A January podcast from To Know the Land features Michael Schuster discussing the Cover It Up research.  To listen, click here.  

Finally, to learn how to identify red elderberry, see the Minnesota Wildflowers page for that species.

References

(1) Schuster MJ, Wragg PD, Williams LJ, Butler EE, Stefanski A, Reich PB. 2020. Phenology matters: Extended spring and autumn canopy cover increases biotic resistance of forests to invasion by common buckthorn (Rhamnus cathartica). Forest Ecology and Management 464. https://doi.org/10.1016/j.foreco.2020.118067.

(2) Schuster MJ, Wragg PD, Reich PB. 2021. Phenological niche overlap between invasive buckthorn (Rhamnus cathartica) and native woody species. Forest Ecology and Management 498. https://doi.org/10.1016/j.foreco.2021.119568.

City Trees Green Up Earlier

 A recent study found that trees in cities leaf out in earlier in spring than those in rural areas.  This post explains what happens as deciduous (leaf-shedding) plants enter and leave dormancy, and how a shift in timing could have ripple effects.

It is December, and the trees are, in their way, asleep. They are dormant, quieted by the declining temperatures and longer nights that signal a time of harsh conditions.

They will have a long nap. Last summer many deciduous trees began covering their buds – next year’s hope of growth – in protective scales. In autumn the leaves gave it up. The chlorophyll, proteins and sugars in their blades broke down or withdrew into branches, trunks and roots to be stored over winter.

As their substance retreats, leaves become liabilities. Through stomates, small pores on the surfaces of their blades, leaves continue to lose water that can’t be replaced from frozen soil. To prevent desiccation, the leaves are cut off.  Invisible lines of cells, called abscission layers, form on the leaves’ petioles, like tear-off lines that mark where they will separate from the trees. Some leaves offered a colorful sendoff and fell. Others, those with abscission layers not quite complete, are still hanging on, rattling in the winter wind.

Although they are dormant now, the trees are primed to renew their growth in spring. After enough cold days have accumulated and as days grow longer, they will begin to stir. As in all aspects of plant growth, timing is everything. If buds break too early, say in an unusually warm February, new growth would likely be damaged by a returning freeze. To avoid this, day length acts as a check. Even if buds have been adequately winter-chilled and temperatures then rise, short days (long nights) are a sign that winter isn’t over, and growth will not resume.

Timing is important not only to avoid freezing, but also to attract pollinators. Insect-pollinated trees and shrubs, especially those that are native here, have long relationships with native insects. Time of flowering may coincide with time of insect emergence and vice versa, each benefiting from the presence of the other. If plants flower earlier than normal, their pollinators may not yet have emerged, or if it's too cold, they may not be active. 

If timing of life events -- phenology -- depends on external cues, what happens when temperature and light are altered? Does a tree’s phenology change when environmental indications change, such as in warmer and artificially brighter cities?

Yes, according to a recent study that looked at satellite and phenological data around the globe (1). According to the study, on average, spring green-up occurs six days earlier in cities compared to rural areas, due mostly to warmer urban temperatures.  When photoperiod – daylength– is factored in, the effect is greater. Urban trees exposed not only to warmer temperatures but also to lights on streets, parking lots, billboards and other artificial sources leafed out an average nine days earlier than rural trees. It's thought that night length, normally a check on early leaf-out, is shortened by city light, and the trees are “tricked” into resuming growth in artificially warmer and brighter conditions. 

The study raises several questions, especially about climate change.  If a warming climate causes trees to green up earlier even in the countryside, would rural darkness limit how much earlier they resume growth? In other words, without city lights, would winter's long nights continue to serve as a check on how early the trees leaf out?

Also, could warm urban winters, made even warmer by climate change, prevent city trees from accumulating enough cold exposure to leaf out early, even if nights are artificially short and spring-like? 

If trees do leaf out and flower early, will allergy season also start earlier? How will insects adapt to the change? Will their phenology shift, too?

These questions can be answered by part by continuing to observe the phenology of plants and animals. Both citizens and scientists are important in that effort. By recording when trees, shrubs and other plants leaf out, flower and form seeds, they contribute to an understanding of what triggers these life events and how their timing might be shifted by environmental changes. 

To learn more about phenology and how to help observe seasonal changes, open the Phenology tab.  

References

(1) Meng, Lin. 2021. “Green with phenology.” Science Vol. 374, Issue 6571 (November 25, 2021): 1065-1066. DOI: 10.1126/science.abm8136

Dr. Meng’s study is also discussed in a National Public Radio interview at https://www.npr.org/2021/11/29/1059861862/climate-change-and-city-lights-are-tricking-trees-into-growing-leaves-too-soon