Sunday, May 3, 2015

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:

-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

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