Unlike animals, plants cannot up and leave when climatic or environmental conditions become unfavourable. Plants survive periods of harsh conditions, like lack of water or cold weather, by entering a period of dormancy.
What is dormancy?
Dormancy refers to the resting period in a plant’s life cycle where it exhibits little or no active growth.
Most plants enter dormancy during the cold winter months when conditions for growth are unfavourable. Dormancy can also be triggered by excessive heat or periods of drought.
Seeds also lie dormant, waiting for favourable conditions to initiate germination.
Why do plants go dormant?
Plants take their cues from the changes in weather, so when the days start getting shorter and the temperatures get lower, the plant’s system is triggered to start entering dormancy.
During dormancy, a plant’s metabolic activity ceases for a time which helps to preserve their valuable energy and resources until conditions become favourable again for growth to ensue.
Many plants require a period of dormancy and cold exposure before they can resume new growth. Trees, especially fruit trees, are good examples of plants that rely on dormancy periods.
How do trees go dormant in winter?
During the active, warm growing months, plants photosynthesize to produce carbohydrates. At the end of the growing season, plants start to move carbohydrates and sugars from the leaves down to the roots to nourish the plant during the cold winter months. This is when leaves start to change colour as the green chlorophyll is replaced by the red, orange and yellow pigments (anthocyanins) which help to protect the leaf during the extraction process.
Dormancy and Pruning
As gardeners, it is important for us to understand when dormancy begins and ends, as this will influence the timing of pruning tasks. Pruning should be done based on the active or dormant state of a plant.
Pruning is usually done to break dormancy and stimulate growth, therefore a good time to prune would be near the end of dormancy as this is when a plant contains a lot of stored energy as is likely to be less shocked by sudden wounds.