High Pruning Walnut

Today, 15th July, is St Swithin’s Day, the best time of the year to prune walnut trees. The saint’s day is a handy way to remember when to brush the cobwebs of your pruning saw and get out to your trees.

The aim is to convert your low value firewood into veneer grade logs. Yes, it really is that simple. Just 10 minutes or so will convert each tree from a mutt to a pedigree. I’ve written extensively about this before – see here.

This year I thought I’d create a short timelapse video (see below) of me working on a lovely specimen of hybrid walnut. This tree is a hybrid between common walnut Juglans regia and black walnut Juglans nigra. It displays typical hybrid vigour and excellent apical dominance (meaning it has a strong growing tip and is less likely to fork). It is growing between two black alder (Alnus glutinosa) trees which have done a great job in protecting it from the wind. Being nitrogen-fixing species, the alders have also helped fertilise the soil which will have benefited the walnut.

This particular tree should have been first pruned several years ago, but it wasn’t. As a result some of the branches were too large for my liking. They will take more than one year to heal over (‘occlude’) which is not ideal, and the tree will have more knots and larger knots at its core. The best pruning method is to cut little and often, i.e. every couple of years, meaning that the branches you remove will be not much thicker than your thumb (a good rule of thumb!) and they will be limited to a smaller inner diameter of the stem. You should never remove branches from more than 50% of the tree’s height. Prune as high as you can although 6m is probably more than enough as it will result in 2x 3m-long saw logs. Ultimately, by high-pruning you are limiting all knots (i.e. former branches) to the core of the log, with all growth outside that knotty core being clear of knots and blemishes. This will create the highest value sawlogs, or even veneer-grade timber.

Watch the timelapse carefully and you will see that with some of the heavier branches I first cut them off at about 50m from the main stem. This does mean double the effort, but the resulting stub which you cut off next tends to fall cleanly without tearing the main stem which is critically important to avoid damage to the tree. The alternative is to undercut before you cut the branch off in one go, but I find this difficult to do especially when working with a 5m+ pole saw. Some saws come with a chisel blade built in which can score the bark and help prevent tearing, but again with larger branches you are better off adopting my technique.

In terms of the equipment, make sure you use a good quality saw. Pruning saws are designed to work on the pull stroke, which is essential when you are working overhead. Personally, I am a fan of Silky Saws, like the ‘Longboy‘ pictured below. Please note, if you click on a link to the pruning saw and go on to purchase one, I will earn a small commission at no extra cost to you (but I appreciate your support!).

Read more about walnut trees