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Notes on Black Walnut Culture

© Wesley Ford

As a forester and garden center manager, it seems I'm always fielding questions about black walnut (Juglans Nigra) trees. There seems to be a mystique about black walnuts that attracts interest in growing them. Perhaps its that reputation for for handsome warm chocolate brown wood thats a favorite in furniture. Or maybe its those delicious nuts that that are at their best when baked into christmas cookies and cakes. At any rate black walnut establishment and culture i often is a popular topic with people I come into contact with.

Here are a few thoughts and hints on how you can grow one or a thousand walnut trees yourself.

First of all be aware that walnuts exhibit a phenomenon called allelopathy. This is a defense mechanism whereby the a plant produces substances that stunt the growth of other plants. Black Walnut roots exude a substance called juglone that is a natural herbicide so to speak. It kills or stunts the growth of many other plant species and thus gives the walnut a competitive advantage. This is how young walnut trees compete and survive in the wild. In domestic landscapes though this can be a problem. Before you bring a black walnut into your landscape you need to know that your plant selection within its root range will be severly restricted. Plant it in your yard with at least a little trepidation.

Walnuts require scarification or exposure to cold in order to germinate. It is not necessary to remove the hull, although doing so may make the nuts easier to handle. There are several methods you can use to effect germination.

The simplest is to simply plant the nuts where you wish to have new trees in the fall. Winter will do the work for you. Punch a hole in the ground 2 to 3 inches deep, plunk in a nut and stomp it closed. If you are going to do a significant sized planting, you may want to plow a furrow, place the nuts in the furrow and cover them. I would suggest planting the nuts rather thickly to allow for bad nuts that won't germinate and to provide adequate number to survive the ravages of the squirrels. Yes - they will dig them up, and I know of no preventative that will discourage them.

In the mid 70s I participated in a direct seeding research project that tried to deal with squirrels. We even cut the bottoms out of tin cans and slid them over the planted nuts. The squirrels dug up the nuts and cans. The only nuts they didn't dig up were the ones that didn't geminate anyway. Go figure! The only way we could establish a stand was to plant them every foot or so and simply allow enough for the squirrels to gorge on and hope a few escaped their purview.

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