Winter Survival Strategies
One reason I created this blog was to follow the progression of the year and the seasons so that I could talk about plants, plant behaviour and plant structures that were “in season”. The question was when to start. The logical place to start for plants, and probably for any biology in North America, would be in the springtime when seeds are germinating, trees are coming out of dormancy and plants that overwinter underground are putting up new shoots. It actually seems pretty bizarre to me that our New Year’s Day is at the beginning of the coldest, least lively part of the year rather than, say, in the springtime when all forms of life are beginning their annual cycles of growth and reproduction. But I suppose that would be a “North-America-centric” view (which, by the way, is likely to be true of this entire blog). And anyway, Plant Stories wait for nobody, so here we are, in January.
Microscope image of a lateral section of a plant shoot apex. The dark areas (there there are lots of small cells) are meristems: source
Most plants are hunkering down at this time of year. Rapid growth isn’t possible with such short days and frost is a major problem if your energy harvesting strategy involves thin, fragile, water-filled solar panels (a.k.a. broad leaves). For the most part, those broad leaves were dropped months ago and now plants are protecting their meristems (the delicate buds where new growth comes from) in one way or another from the cold.
One strategy, that of perennial shrubs and trees, is to cover the meristems in thick, hard scales to form a bud (excellent winter bud pictures over at Nash Turley’s blog). The shape and arrangement of winter buds depends on the plant, and if you know what you are looking for, it is still possible to identify the plant species in the absence of leaves and flowers just by looking at the buds. Another strategy of perennials is to hide the meristems underground where they are insulated by the soil. Everyone who has planted tulip bulbs knows about this way of overwintering, but it may not be obvious that when you’re walking through the park on the cold hard soil, beneath your feet lie the bulbs, tubers, corms and rhizomes (all different underground-bud-protecting structures, more on those in another Plant Story) of lots of the plants that will come up in the springtime.
A head of garlic is a type of Bulb: many lily-type plants protect their meristems in these short shoots surrounded by fleshy leaves and a papery leaf covering.
The other overwintering plants hidden in the frozen soil are the annual plants. These employ a different strategy; instead of preserving meristems to grow again in the spring, they put all of their energy into producing seeds while the growing conditions are good and then die off in the winter. The seeds, protected in their hard shells and insulated underground, remain dormant until the ground warms up again, and then start a new generation.
And then, of course, there are the ones who tough it out: the evergreens. The cone-bearing trees (and some of the broad-leaved shrubs) with wax-coated, leathery leaves that can withstand the cold continue to photosynthesize throughout the winter, although even they must slow down all of their processes and arrest growth. It is an expensive strategy, but at least they won’t have to completely rebuild when the days start to get longer again.
All-in-all it’s a tough time for plants and a challenging time to come up with good Plant Stories. My goals will be to look for some less-obvious botanical examples and keep coming up with interesting anecdotes from the perspective of plants.
