Pruning Chinese Chestnuts

The natural growth form of the Chinese chestnut is low and spreading, much like that of an apple tree. If permitted to grow the way it wants to, the typical Chinese chestnut will have large, horizontal limbs radiating out from the trunk starting from a foot or less from the ground. These limbs can make it challenging or even impossible to get mowing equipment under the drip line of the tree (Figure 1). This is not a problem for chestnuts grown for feeding wildlife, but it is unacceptable for commercial nut production. Because chestnuts are harvested from the ground, the ground cover has to be mowed short for the nuts to be harvested at a commercial scale. For this to happen, the trunk of the tree needs to be free of limbs up to a height that permits access for both the equipment and its operator, all the way up to the base of the tree. A clear trunk up to 5 feet or 6 feet is usually adequate, depending on the height of the mower and operator.
One way to get a clear trunk on a Chinese chestnut is by pruning. This will work as long as some basic rules are followed:
Rule #1: Do all your pruning during the dormant season, between November and February. Never do any pruning between March and October. Pruning in the wrong season may result in sap flow which may attract picnic beetles (family nitidulidae). Picnic beetles frequently carry the spores of the oak wilt fungus Bretziella fagacearum on their legs. If they come and walk around on open wounds in your trees, they may start a financially devastating outbreak of oak wilt in your chestnuts.
Rule #2: Never prune a limb flush with the tree trunk. The cut should be made just beyond the “branch collar” which is the swelling on the limb where it attaches to the trunk (Figure 2). Cutting flush with the trunk will create a larger wound taking longer to heal and risks the entry of decay fungi into the heartwood of the trunk.

Rule #3: Do not prune branches less than ¾ inch diameter at the point where they reach the branch collar but try to get them removed before they reach 1 ½ inches diameter.
Rule #4: Start pruning at the base of the tree, and work your way upward, but don’t prune off more than 1/3 of the top in any one year. Over-pruning risks permanently stunting the tree’s future growth.


If you opt for obtaining your 5 to 6-foot clear trunk by pruning, you should realize the trees will resist your efforts. The trees will continually send out new branches from your newly cleared trunk, and this process will continue until the crown of the tree gets big enough to shade the trunk all day – usually around 15 years. This means you will be producing mountains of prunings from every acre, every year for 15 years. If this sounds like a lot of work, I can guarantee it is (Figure 3). Fortunately, there is an easy, low-cost alternative to pruning for a 5-to-6-foot clear trunk: grow your trees in a 5 or 6 foot tall ventilated tree shelter such as those from Plantra (Figure 4). Growing chestnuts in ventilated tree shelters has multiple benefits: they dramatically reduce tree mortality from all causes, they protect the trees from browse damage from deer and rabbits (and from rubbing by buck antlers to a limited extent), they make the trees grow faster and start bearing nuts years earlier, and they suppress the growth of side branches. With tree shelters, you can achieve a 5 or 6 foot clear trunk with little or no pruning at all. Any side branches growing inside the tree shelter stay small and never reach the ¾ inch diameter size and don’t need to be pruned. Occasionally, two tops come out of the tree shelter at the same time. In that case, just pick the best one and prune the other one off.


Once your trees have a 5 or 6 foot clear trunk, many will never need any more pruning for the rest of their lives. What little pruning is needed is to establish the basic shape and structure of the tree. Branches that come out from the trunk at an angle sharper than 45° should be pruned off to prevent the formation of weak crotches that may break off from wind, ice, snow, or a heavy crop of nuts. The ideal crotch angle is 90°, with the limb perpendicular to the trunk, but any angle down to 45° is acceptable (Figure 5 & 6).

Occasionally too many branches emerge from points too close together on the trunk. This results in crowded limbs (Figure 6). Branches should be thinned so they are well-spaced, giving priority to keeping branches with the best crotch angles. Sometimes a low limb may sag from the weight of a heavy nut crop. You can flag those limbs for later removal.
Some Chinese chestnuts will send up an annual crop of “basal sprouts” – branches or shoots growing from the trunk at or near ground level. These can catch leaves, twigs, burs, and even nuts, preventing them from reaching the ground. They may also interfere with mowing, so it’s best to remove them.
As long as you follow the basic rules for pruning, and get your trees properly shaped at a young age, your Chinese chestnuts should remain low-maintenance and trouble-free for many years, decades, or even centuries.
