As we approach Autumn, we are tempted to give our trees and shrubs a good trim and tidy to keep them looking good over the Winter months when one doesn’t venture out to work in the garden as much.
By understanding a bit more about trees and their needs, we can better care for them and keep them looking their best.
Deciduous trees (those that lose their leaves over the Winter) are generally best pruned during their dormant season.
After the leaf fall in the Autumn
- Some of the nutrients stored in the leaves are recovered before they are shed.
- Trees are trying to store as much energy in this period to support them during the dormant season.
Before the buds break and new leaves emerge in the Spring
- Trees expend a lot of energy to ‘wake up’
- They rely on a full and healthy leaf canopy to replenish all this used up energy.
Pruning carried out during these periods can lead to stress in trees, potentially causing them to go into a state of decline.
As always in nature, there are exceptions to the rule. These are just a few examples…
- The sap in some trees starts rising a lot earlier, before the onset of Spring. Trees like the Silver Birch will ‘bleed’ from pruning wounds if works are carried out too late in the Winter. They are best pruned in the heart of Winter and before the end of January ideally.
- Silver Leaf is a fungus found on Apples, Cherries, Plums etc. It causes silver leaves and branch die-back. The spores of this fungus are active September to May and can colonise fresh pruning wounds during the Winter. Pruning of these trees is best carried out in the Spring when the sap is rising and can ‘push’ the spores out of the vascular system and the trees are growing actively.
- Another exception to this is large and very mature trees, like our ancient and veteran Oaks. New research indicates that these are best pruned in the Summer when they are actively growing and able to begin ‘healing’ the pruning wounds straight away, whilst still making energy at the same time from the remainder of the leaf canopy. Care must be taken to only remove what is absolutely necessary to avoid placing stress on the trees energy reserves.
Evergreen trees and shrubs slow down growth over the Winter months. However, they are still photosynthesising and rely on the energy produced by their leaves to keep them ‘ticking over’. Much like a hibernating bear, it’s body is still active but it’s doing the bare minimum to survive. So removing branches in the Winter reduces their ability to produce food without them being able to grow more leaves to make more energy.
These are best pruned in the Spring and Summer months.
The weather is also an important factor to consider.
- Avoid pruning trees and shrubs in extreme weather conditions.
- In very cold and frosty conditions, freshly exposed tissue can be damaged by the frost.
- In very hot weather, removing too much leaf cover at any one time can cause sun-scald. Yes, trees can actually get sunburn! Species with thinner bark like our lovely Beech trees can really suffer from this as previously shaded limbs are now exposed to direct sunlight.