Pruning a Pecan Tree: Training Young Trees and Leaving Old Ones Alone

Why the leader is everything

A pecan grows into a tree that will carry an immense weight of wood 80 feet (24 m) in the air for a hundred years. Any structural weakness built in during the first decade eventually tears the tree apart in a storm, and by then the limb is too big and too high to do anything about. This is the single reason to prune a young pecan: to end up with one dominant central trunk and well-spaced side limbs attached at wide angles.

Left alone, a young pecan often forks into two competing leaders of equal size. The junction between them holds bark trapped inside it, which never knits into wood, and that included bark is where the tree splits twenty years later. Removing one of a pair of codominant stems takes three seconds with pruners at year three, and a crane at year thirty.

Narrow crotch angles fail the same way. A side limb leaving the trunk at a sharp upward angle grips poorly; one leaving at 45 to 60 degrees from vertical is far stronger. Choose the wide ones and remove the tight ones while they are pencil thick.

Training the first ten years

Prune in late winter while the tree is dormant and before the buds swell. Cuts made then close fastest, and you can see the whole structure with no leaves in the way. Keep the work light each year; removing more than about a quarter of the live crown sets a young pecan back badly and delays first cropping.

1. Year one: head the whip At planting, cut the unbranched whip back by a third to a half to a healthy bud. This forces strong shoots low on the trunk and rebalances the top against the roots lost when the tree was lifted.
2. Years two to three: pick one leader Choose the straightest, strongest vertical shoot as the permanent leader. Cut back or remove any shoot competing with it. Do this every year without fail; pecans regrow competing leaders continually.
3. Years three to six: leave the low shoots on Keep short side shoots on the lower trunk rather than stripping them. They feed the trunk and thicken it, and they shade the bark against sunscald. Shorten any that grow vigorously enough to rival the leader, but do not remove them all at once.
4. Years five to ten: build the scaffold limbs Select permanent side limbs spaced 12 to 18 inches (30 to 45 cm) apart up the trunk and arranged around it rather than stacked on one side. Favor wide angles. Remove limbs directly above or below one another.
5. Years six onward: raise the crown gradually Remove the lowest temporary shoots a few at a time until the lowest permanent limb sits at the height you want to walk or mow under, typically 6 to 8 feet (1.8 to 2.4 m). Take three or four years over it, not one season.

Photograph the young tree each winter from the same spot before you cut. Comparing this year's photograph with last year's shows immediately which shoots are winning and whether the leader is holding its dominance.

Mature trees: less is more

Once the framework is built, a pecan needs almost nothing. Remove dead, broken and rubbing limbs, and take out anything hanging low enough to be in the way. That is the whole job in most years, and it can be done from the ground on the parts you can reach.

Do not top a pecan, and do not thin the crown out heavily in the hope of more light. Large cuts on old pecan wood decay rather than compartmentalise, and the tree responds by throwing dense vertical watersprouts that shade the crown worse than before. A tree that has been topped never regains sound structure.

The one heavy job worth doing on a mature planting is removing whole trees. Pecans planted at what felt like generous spacing close up completely after twenty-five years, and a crowded orchard stops bearing on the shaded inner branches. Taking out every other tree feels drastic and roughly doubles the crop on those that remain within a few seasons.

Pruning, thinning and alternate bearing

Pecans bear heavily one year and barely at all the next. A huge crop drains the tree's stored reserves into kernels, leaving too little to initiate flower buds for the following season, and the cycle locks in. Once it is established the tree keeps it up for decades.

Winter pruning is a blunt way to soften the swing. Cutting back a proportion of the shoot tips on an off-year tree in late winter removes some of the buds that would have carried an excessive crop, and moderates the following on-year. It helps, but it is imprecise.

The better tool is removing nuts in early summer on a heavy year, once the clusters are visible and the tree has finished its natural drop. Taking off a third of the clusters, cluster by cluster on the reachable limbs, leaves the remaining nuts larger and better filled and lets the tree set flower buds for next year. On a big tree you cannot reach most of it, which is the honest reason home pecans alternate more than commercial ones do.