In Part I of this series (if you missed it, find it here – Plant Dormancy – More To It Than The Eye Can See (Part I)), we covered the general elements of winter dormancy – how plants prepare for it by manufacturing and storing food, how things like temperature and length of daylight trigger the start and end of dormancy and the process of vernalization – how certain plants and seeds require a period of cold before they can germinate or blossom in the spring. Here in Part II, we cover how specific plant elements can be affected by dormancy.
An Overview of Dormant Plant Elements
Seeds – In northern climates, many seeds are genetically programmed to go through a process called “cold stratification.” The seeds need to be exposed to cold temperatures for a long enough period to release hormones that trigger the end of dormancy for the seed. Ideally, the soil surrounding the seed will have thawed to provide it with enough moisture to begin its germination.
Tree Buds – Buds, such as those found on cherry trees, are often covered with protective scales as they enter into dormancy, and require a particular amount of chill hours before opening. A warm winter can delay or thwart this from happening.
Perennials – The woody parts of perennials, trees and shrubs can handle the cold, and while the more vulnerable leaves and stalks may die off, the roots and bulbs beneath the ground remain viable, allowing the plant to live off stored food until spring arrives.
Evergreens – Evergreens have special leaves that resist cold and retain moisture. These include the needle-like leaves of pines and spruces as well as the tough, waxy, broader leaves of species like hollies. Photosynthesis in evergreens can continue if they have sufficient water to distribute nutrients, but this process is greatly slowed due to cold temperatures.
Flower Bulbs – Bulbs form in the heat of summer as they go through a process called baking. The cooler, wetter fall weather stimulates root growth, but winter’s cold is what’s needed for stem growth to be triggered. The carbohydrates in the bulbs begin as stored starch because this is a more concentrated form of energy than a simple sugar, but since starch isn’t water soluble, it’s difficult to move to distribute nutrients. When cold weather arrives, enzymes in the root are triggered to convert the starch back to a water-soluble sugar, allowing the nutrients to flow to the plant’s tips and push their shoots through the ground before other plants begin to come out of their dormancy.
So while the garden may look like it’s sleeping, know that it’s working hard to make its beautiful, vibrant and much-anticipated re-appearance in spring.