Confused Plants and Warm Winters
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Confused Plants and Warm Winters
Allison Kosto
MSU Broadwater County Extension Agent
It’s sure hard to complain about the mild winter we’ve been having. With the exception of some gnarly ice, the roads have been delightful; The winter calvers aren’t complaining; And the plants are thoroughly confused. There have been multiple reports in the county and across the state about plants coming out of dormancy early, such as shrubs budding, tulip bulbs popping and growing grass. After a brief moment of happiness that spring may be on its way, the reality sets in of knowing that winter is far from over. Plants showing signs of life in January is not necessarily a good sign and may have implications later on.
Basically, all plants in northern climates go through dormancy. This is a natural pause on growth that plants enter in the fall in response to day length and/or temperature changes. There are two phases of dormancy. The first phase is called endodormancy, also called “deep dormancy.” This is an internal state of dormancy in which a plant cannot grow even in warm conditions until certain conditions are met. These conditions are typically a threshold of “chilling hours” where a plant has to be at a cool temperature (typically between 32 and 45°F) for a period of time. This length of time varies between plants.
After a plant completes the necessary conditions of endodormancy, it moves into ecodormancy or quiescence. This is a shallower state of dormancy where a plant is potentially ready to grow when given the right conditions. Most years, plants look at the weather and maintain their dormancy even though the plant may be physiologically ready to come out.
That’s where years like this one become an issue. By December or January, enough time has passed for some plants to complete their endodormancy cycle. As a result, unseasonably warm temperatures can trick plants into coming out of the ecodormancy phase early.
Here’s the bad news. Once a plant exits the dormancy phase, it cannot “go back in again.” It can pause or slow growth but will never be fully dormant again. This means that there is an elevated risk of damage depending on what happens for the rest of the winter. On the positive side, a lot of the adapted perennial plants, such as tulips or daffodils, are very hardy and can withstand some frost or freezing damage. They may recover just fine. If they emerge early, simply cover them with straw or mulch.
Trees that bud or leaf out early may experience branch and tip dieback and less flowering and/or fruit production. It is unlikely that it will kill the entire tree, but it can certainly cause damage. The best strategy is to prune out the dead areas. It is extremely important to water trees in years like this one throughout the winter, especially evergreen trees but even deciduous trees if you suspect they are coming out of dormancy. Do not water right before a temperature drop or when the ground is frozen.
Unfortunately, there isn’t much you can do to prevent plants from breaking dormancy too early. It’s part of nature’s cycle. However, one potential strategy is to avoid planting plants that are susceptible to coming out early in locations that may speed up dormancy breaks such as the south side of a building or near concrete. Take a walk regularly throughout your yard on mild days to take note of plants that appear to be coming out of dormancy. Continue to monitor them throughout the spring and early summer for damage and avoid fertilization until it looks like the plant is recovered.
Living in Montana is always an adventure as is gardening. Enjoy the mild winter and make the best of it because it might not be the same next year! For gardening or plant questions, contact the MSU Extension Office in Broadwater County at 406-266-9242 or allison.kosto@montana.edu.
