The study of the cycle of life throughout the year and the events that take place, charting the growth and development of a tree is known as phenology. If we choose to observe and follow this series of events, we can learn to further appreciate the wonder of trees.
So let us begin in following this life cycle in early spring, a time when trees awake from the winter period of arrested growth and its stores of carbohydrates and food energy are abundant. These carbohydrates are used to initiate a new growth of root hairs, increasing the surface area of tree roots and kick starting the processes of water and nutrient uptake, preparing our tree for its first flush of buds. This cycle period is known as breaking dormancy, and soon enough, as the spring season continues, new soft tissue will begin to form and buds will burst in to life.
This period of vernal growth provides our tree with its first leaves, which will then begin to photosynthesise, supplying more food energy and furthering the processes of primary growth, whereby the apical meristems in shoots elongate, until all the winter buds have flushed out their leaves. We may see further signs of new growth, known as adventitious growth, a little later in the year - around July/August - to counter any spring leaves that may have been eaten by greedy insects!
It is especially important at this time that we understand the outside influences that may have a negative effect on our tree. For instance, now is not the time to consider pruning. Being that all of its energy reserves have been used in flushing out spring growth, by pruning and leaving not enough new growth to provide more energy, we’re effectively starving our tree!
The following stage in the phenological cycle of our tree is termed as a period of secondary growth, the result of activity within the vascular cambium that increases stem thickness. So as our tree grows up, it also grows out.
Some trees, termed as dioecious, may have distinct male and female plants within the same species, producing either male or female catkins and flowers. Other trees, being monoecious, for instance quercus robur (English Oak) produce both male catkins and female flowers.
During the period of spring leafing, we’ll generally begin to notice the long and drooping form of male catkins loaded with pollen grains. Being wind pollinated, the catkins hang in such a manner so as to catch the wind, releasing pollen with the intent of cross pollinating another species member. Soon after, in the period known as fruiting, female flowers form at the base of new leaves and open to display pollen receptive stigma and ovules. In following, the process of seed development continues.
Join us again as the seasons change and we further explore the phenological cycle!