Why do plants have to find a way to adapt in the winter?
All plants require sunlight and water. During the winter months, the shorter days provide less sunlight. Freezing temperatures often mean that water is frozen (solid) and inaccessible. Freezing temperatures can also cause the water inside the plants to expand and break open plant cells.
How do the plants adapt?
(Spoiler: what you see in the winter are often essentially ‘sleeping’ plants.) The Heard gardens and nature preserve plants are primarily native species adapted to our local weather and seasonal patterns. First, understanding their lifecycles helps explain how the species survive during the winter.
Plant lifecycles are classified as annual, biennial, or perennial. Annual plants complete their entire lifecycle within one growing season. Biennial plants complete their lifecycle in two seasons. And perennials live for several years or more.
Annual Native Plants
Because annual native plants only survive one season, they often adapt to this situation by producing seeds before the cold of winter or drought conditions arrive. Then, the plant dies, leaving behind the hope for the species to live on in the seeds. These seeds have adapted mainly to sprout once stressful periods (cold or drought) have resolved. They sit waiting for spring to come and bring sufficient sun, warmth, and rain for them to grow (or, in the case of drought, for cooler, wetter weather to arrive). As a result, no live specimens are present during the winter. Some annual species may survive drought depending on the severity and unique adaptations.
Perennial and Biennial Native Plants
Because perennial and biennial native plants live more than one growing season, they must find additional ways to adapt to winter conditions besides annual reseeding methods. While some plant species stay green throughout the winter (“evergreens”), most of our native perennial plant species do not.
Instead, the other species go through a process called “dormancy.” While the plant parts exposed to the weather die back for many of these species, the roots stay alive, storing nutrients to survive the winter. (Some plants have adaptations that may allow the stems to stay alive.) Different species may also have other adaptations that keep the roots from freezing.
These species that die back in the winter will retain their dead appearance until spring’s warmth and increased sunlight break their dormancy. In other words, as Mother Nature returns from her winter slumber or rest during drought, things will begin to look better and better slowly.
Why do I see green plants in landscapes around town during the winter and times of drought?
In the winter, plants you see around town that remain green the whole time are either non-native or are evergreen native species. The non-native plants used in ornamental landscaping are adapted to growing in cooler climates than ours (pansies and cabbages are a good example). Because our native wildlife has not adapted to using these plants as food or shelter, they often provide little benefit to the ecosystem. In times of drought, many of the species you might see surviving in landscapes do so because they receive supplemental water. This practice does not always use environmentally sustainable methods.
What happens during periods of extreme cold, heat, or drought?
When the conditions of our climate go beyond their norms (whether much hotter, colder, or dryer), our native plants may not survive with their adaptations alone. The survival rate may be less than usual, and fewer plants will return. As our climate changes, we may see more of these losses.
Additional information
Here are a few informative links that go into more depth on these topics:
https://kpu.pressbooks.pub/plant-identification/chapter/plant-life-cycles/