The Race Against Time: Spring Ephemerals

An ephemeral plant is a plant which has a very short life cycle, which takes place during a brief window of opportunity for growth due to environmental factors.

In my neck of the woods, the type of ephemeral plant that we see is the spring ephemeral. Spring ephemerals are perennials which grow in wooded areas. Spring ephemerals are wildflowers; the most crucial characteristic to keep in mind about them is that they are small/short.

Sunlight is a resource which, in the forest, is in short supply; woody plants (shrubs, trees) compete with each other for sunlight by growing higher than others. This strategy isn't an option for spring ephemerals.

So what can a spring ephemeral plant do in order to survive and reproduce in a place where woody plants take up all the sunlight? Well, that's the key... they don't take up quite all the sunlight, not in northern climates where deciduous trees shed their leaves each fall and produce new ones each spring. There's plenty of sunlight hitting the forest floor between fall and springtime.

Spring ephemerals are plants which take advantage of the brief window of time between the snow melt and the closure of the canopy, where there is abundant sunlight hitting the forest floor, warmth, and reasonable insect pollinator activity.

Carpet of Dicentra sp. leaves in the wooded section of the Notre-Dame-des-Neiges cemetery, taking advantage of the brief window of sunlight to spread their leaves and make as much sugar as possible

Spring ephemerals are perennials in large part because the window of resource availability is so brief that it is essential to have some form of stored energy to get a head-start -- so spring ephemerals tend to have bulbs, rhizomes, or tubers which store energy over the winter and can be used to put out a spurt of rapid growth before sunlight is received to produce more energy.

Some spring ephemerals even set their flowers in the fall prior to their reproductive season (eg T. farfara) to broaden even more the amount of time that they can take advantage for reproduction early in the year.

The period of sunlight availability is a few weeks at most, so the plants must race to put up their leaves as quickly as possible to start producing sugars that can be used to make their flowers with the metabolically expensive nectar that attracts pollinators, and the similarly expensive seeds and fruit that are produced for reproductively successful flowers. They have all sorts of interesting adaptations for this, which I have talked about in a few of my posts about spring ephemerals already on this blog. A few examples of spring ephemerals found in Ontario and Quebec include:

-Dicentra cucullaria

-Dicentra canadensis

-Sanguinaria canadensis

-Erythronium americanum

-Trillium spp.

-Caltha palustris

-Claytonia spp.

-Thalictrum dioicum

-Thalictrum thalictroides

-Caulophyllum thalictroides

-Tussilago farfara (introduced)

-Scilla siberica (introduced)

And others

The spring ephemerals had better hurry. The leaves are already starting to emerge on some of the trees, like this Salix x sepulcralis (weeping willow) I noticed nearby already looking green and lively:

Salix x sepulcralis with leaf buds already opening

Trout Lily - Erythronium americanum - Érythrone d'Amérique

Erythronium americanum (trout lily, fr: Érythrone d'Amérique) is a very long-lived forest understory perennial from the family Lilaceae. It is a spring ephemeral (meaning that the plant emerges and senesces before the forest canopy has closed). This plant is most easily identified by its mottled grey and green leaves; each plant produces either one or two of these leaves, which are arranged basally. The flower is yellow, sometimes with red or purple spots toward the inside; there are six tepals, which can be heavily recurved. The flower is slightly nodding, pointing the ground.

E. americanum - all major points of anatomy visible

The above photograph was taken without damaging the plant; I gently bent the flower stalk down and righted it when I was done. These plants rely on a very narrow window of sunlight in the early spring to store energy in the rhizome for growth and blooming the following year, so it is best to damage them as little as possible.

Note that the anthers are of varying lengths and sizes. They look red here because they have not yet opened to expose the pollen (this flower had opened the same morning that I took the photo).

This flower blooms extremely rarely; some estimate that only about 1/60 plants will bloom in a given year. My observation suggests that this number could be lower in some places, such as where I took these photographs at QUBS. The plants take several years to achieve reproductive maturity, and once achieving it will bloom only occasionally.

E. americanum  - note the heavily recurved sepals

This plant is particularly suitable for certain types of pollination studies where one wants to know which individuals are successfully pollinating other individuals. This is because there is a naturally occurring difference in pollen colour in some of these individuals; the general population has yellow pollen, while occasionally an individual has brown pollen. This allows researchers to take an individual with brown pollen, plant it in amongst individuals with brown pollen, and actually track exactly where the brown individual's pollen ends up going. There are techniques to do this with plants which don't have different flower morphs, but they generally entail putting a fluorescent dye on the pollen and this does somewhat alter its characteristics, eg weight (and is therefore a potential confound).

E. americanum

E. americanum is listed as secure in Canada and secure in most of its US range, except in Iowa where it is threatened.