By Joe Zeleznik, Forester

NDSU Extension

My wife and I have a couple of really cool apple trees in our yard. Each tree has multiple varieties grafted onto the main stem. I haven’t counted lately, but I think one of the trees is up to about a dozen different varieties. The harvest is different each year, which is fascinating.

Right now, though, certain branches are still holding onto their leaves, while others have lost them all. Most deciduous trees, including apples, should have lost their leaves by now, so this isn’t normal. What’s going on?

Quite simply, those specific branches didn’t harden up completely for winter. This tells me that those varieties are borderline hardy for our area. They really need a longer growing season, and a long autumn that allows them to go dormant naturally. They rarely get those conditions in our area, as we’re so far north.

Yet other varieties go dormant just fine. It’s crazy.

I’ve noticed a lot of other trees around that haven’t lost their leaves. For some species, this is perfectly normal, as they hold onto their leaves into winter naturally, even though they’re fully dormant and hardy.

Ironwood is one species that has this characteristic of holding onto its leaves in the winter. The technical term for this is “marcescent.” It’s a normal behavior for ironwood and several of the oaks.

Other things can cause trees to hold onto their leaves well into the winter. Some diseases or insects can kill or damage leaves to the point where they don’t fall off their branches in autumn. Those branches might not survive over the winter and therefore won’t grow new leaves next spring.

At the other extreme, we sometimes water and fertilize trees too much and they won’t shed their leaves naturally. It sounds counterintuitive. How can giving the tree the things it needs for growth and health be causing a problem?

Quite simply, too much water or fertilizer keeps trees vegetative – growing – well into the fall and they don’t harden up in time for winter. I often recommend that people avoid fertilizing after July 4, and apply some drought stress to their trees in August, to slow down their growth.

It seems illogical, but stressing the trees a little bit in late summer helps them go dormant on time.

Let’s go back to those branches on my apple tree that are still holding their leaves. What should I do?

Really, there’s nothing I can do. Those branches didn’t harden up properly and all I can do is wait. Removing the leaves, one by one, won’t change anything. I’ll just wait for nature to take its course and the leaves will likely fall off in early spring.

There is one thing I can do for the apple trees to help them survive the winter. Protect them from rabbits! But that’s a whole different story.

NDSU Agriculture Communication – Dec. 13, 2023

Source: Joe Zeleznik, 701-730-3389, joseph.zeleznik@ndsu.edu

Editor: Kelli Anderson, 701-231-7006, kelli.c.anderson@ndsu.edu