On phenology

“Phenology” is a fancy word that ecologists and botanists use when they talk about sequencing. In nature, within a cohesive ecosystem, things happen in a particular sequence. Within a forest, understory plants emerge, bloom, and go dormant in early spring, before the mid-height shrubs or canopy trees leaf out. This sequence ensures that each type of plants receives the light it needs to complete its life cycle. This photo, taken in my backyard yesterday, is a very stark example of phenology in action:


The large tree in the center that looks like it’s dead is a white ash, and it’s very much alive. It is a native tree, and it leafs out very late, allowing the understory plants to do their thing. Notice the flowering dogwood in bloom, not being shaded out by the taller ash tree. Now notice the large, dark-green  Norway maples on either side (they’re in my neighbors’ backyards). They are already fully leafed out, so they will shade out anything growing beneath them. When Norway maples escape into our woods, which they do easily because they produce copious amounts of seeds, they gradually shade out and kill the understory.

Within any ecosystem, the plants have evolved together and they are adapted to live together. Another fascinating example of phenology in action is the bloom sequence of closely related species. In a nutshell, you can predict that if flowering dogwood is in bloom, none of the many closely related species of dogwood will be in bloom at the same time. Plants that bloom simultaneously are competing for the services of pollinating insects, and closely related plants, like members of happy families, do not compete. I grow three native dogwood species, flowering dogwood (Cornus florida), grey dogwood (C. racemosa), and redosier dogwood (C. stolonifera). They bloom in that order every year–right now, flowering dogwood is at its height (see the photo below), grey dogwood has large flower buds, and redosier dogwood is just beginning to show buds.


Phenology applies to many interactions between unrelated species as well. For example, when redosier dogwood is just about to bloom, I always see many tiny, silvery eastern blue butterflies fluttering around the plants. It turns out that their caterpillars feed on the flowering parts of this species, so blooming of redosier dogwood predicts the emergence of eastern blue butterflies.

Go out an explore nature today, and take your kids–you will make fascinating observations.


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