This week in the garden we will continue our winter pruning of apple and pear trees. It is important to do this when the trees are still dormant, that is when the buds have not yet started to open. Trees store most of their energy reserves in their sap, and in winter, deciduous trees’ sap sinks. It is only when the sap begins to rise, as indicated by swelling spring buds that the plant’s energy is ‘coming out of storage’ so to speak. By pruning tree branches before the sap rises we are only taking away a minimal amount of the plant’s energy reserves. (If, however we wait until there is blossom and leaves on the tree before pruning we are removing a lot more of their stored energy and stressing the tree unnecessarily!)
When pruning fruit trees, we will also be collecting scion wood. Sion wood is the wood that has grown in the previous year, in other words last season’s growth. These are the tips of branches that are only one year old. If we keep these branches cool and do not let them dry out, they can be used later on in the spring to graft onto apple rootstocks to make new fruit trees.
We are starting to re-design the seating circle, the area just inside the entrance gate. We will begin by cutting back the plants, and improving the soil in this area by adding compost from our compost bays.
We will be tidying up the front borders, weeding and cutting plants.
The pond is growing a fresh layer of duckweed, that little green plant that is covering over the water again. We will remove this with a net.
Here’s a brief note on the fascinating subject of dormancy for those who enjoy reading about the internal workings of plants! What does it mean for a tree or fruit bush to be dormant? It is rather like when animals hibernate as a winter survival strategy. Deciduous trees shed their leaves in preparation for dormancy, because having leaves uses up energy and makes trees more vulnerable to frost. In winter, trees slow down, their metabolism, (energy consumption) and growth slows, and they store most of the energy they created during the summer in reserves in their sap. Because trees lose their leaves in winter they are not able to make any new food for themselves, so what they have in energy reserves they use slowly and only for essential functions.
To survive winter cold, a tree begins its preparations in late summer as day length shortens. Cold acclimation occurs gradually and includes a number of physiological changes in leaves, stems, and roots. The autumn colour on leaves is the most striking outward manifestation of these changes. However, inside the tree there are three other strategies trees employ to prevent living cells from freezing. One is to change their membranes during cold acclimation so that the membranes become more pliable; this allows water to migrate out of the cells and into the spaces between the cells. The relocated water exerts pressure against the cell walls, but this pressure is offset as cells shrink and occupy less space.
The second way a tree staves off freezing is to sweeten the fluids within the living cells. Come autumn, a tree converts starch to sugars, which act as something of an antifreeze. The cellular fluid within the living cells becomes concentrated with these natural sugars, which lowers the freezing point inside the cells, while the sugar-free water between the cells is allowed to freeze. Because the cell membranes are more pliable in winter, they’re squeezed but not punctured by the expanding ice crystals. These cellular mechanisms are intended to keep living cells from freezing. That’s the key for the tree; don’t allow living cells to freeze.