Once the trees have finished producing truffles for the season it is time to ensure all husbandries are completed before the truffle growing cycle starts again and the truffle starts to form. Late winter/early spring is an ideal time to prune most trees just as their buds are swelling. Leafless stems make it easy to see where to cut (not so if you have evergreens), dead stems make their presence known, and with coldest weather past, chances for cold damage near cuts are minimised. Warmer spring weather also promotes rapid healing of cuts.
Though the requirements for different tree and truffle species differs, along with your site conditions and tree age, there are certain tips that can be used by everyone. I tend to lean towards the way many French truffieres prune their trees rather than what you see at many Australian truffieres. Because they French soil temperatures are a lot more like ours here in New Zealand it makes more sense to me to adapt the same technique that allows for maximum sunlight to hit the soil at the base of the tree and increase high soil temperatures to promote truffle growth. Australia can get away with a bit more shade caused by remaining foliage, as the temperatures are so much higher so the truffle remains happy. Take what you like from this it is in no means scientific or exhausted, but these are my observations and techniques I am thinking about when I am pruning our trees at the Southern Cross Truffles block in Waipara, North Canterbury:
- Prune to maximise sun around the whole tree while keeping enough foliage to keep the tree healthy. Think of bonsai trees but on a bigger scale.
- I aim to keep everything to a height where I can prune without a ladder and just using hand loppers. It helps to keep the tree “forever young” and at the same time is a lot easier not having to use special machinery and equipment.
- With young trees prune to train them to become structurally sound, to make them easy to care for (no low hanging branches that could get in the way when spraying or any tractor work) and start forming them so sunlight is distributed evenly throughout the tree and the ground at the base.
- As young truffle trees grow, remove lower branches gradually to raise the crown, and remove branches that are too closely spaced on the trunk. Prune to shape young trees, but don’t cut back the leader until they have reached the desired height.
- Tailor each cut to the response you want from the tree. Where you want increased branching, shorten a stem. Where you want less congestion remove whole stems or limbs.
- When simply shortening a small branch, make the cut at a lateral bud or another lateral branch. Favor a bud that will produce a branch that will grow in a desired direction. The cut should be sharp and clean and made at a slight angle about ¼ inch beyond the bud.
- On any truffle tree, cut away suckers (hazels are especially bad) that shoot from the base of the tree, they soak up the plant’s energy, look unattractive, and block the sun so that it can not heat up the soil temperatures for successful truffle growth.
- Remove undesirable wood – dead, broken, and crossing branches and branches that grow back towards the centre of the tree.
- Always use a tool appropriate to the job. Make sure that your pruning tools are sharp and clean, because plants heal quickest when cuts are clean. I use secateurs, loppers, pruning saw, pole saw/lopper, forestry ladder (for our bigger trees) and for the more serious pruning my birthday chainsaw!
- Take your time and really look at the structure of the tree before getting stuck in chopping branches off willy nilly. And remember we are always aiming for the best tree for growing truffles not just the best tree.