Gardening Around Black Walnut Trees

Our plot of land is about 0.10 acres, and right in the middle of the plot is a fully grown Black Walnut Tree. A lot of gardeners would see this tree and say, “NOOOOoooooooo!!!!! CHOP IT DOWN!!!”

I think that is just silly.

Black Walnut Trees have a bad reputation for being Killer Trees because they excrete a chemical called juglone, which is toxic to SOME plants.

Some. Not all.

Our early garden in the background with the walnut on the right

 In fact, there are a lot of plants that don’t give a hoot about juglone at all. And black walnut trees produce a lot of – take a guess – yes, walnuts. Which are delicious! That is why I am actually quite happy to have our fully mature and producing walnut tree. This year, thanks to some proper pruning and a good season of fertilizing and watering, our tree produced roughly 15 gallons of walnuts (hulled, but still shelled). We have been eating walnuts every day all winter and we still have nuts to be eaten.

All that said, it is very helpful to know how to garden AROUND this tree, because it IS a giant tree that can kill some of my plants – namely, anything in the nightshade family. That would include tomatoes, peppers, eggplants, and a few others. The tree is also fully grown, so it produces a lot of shade and takes up a lot of water.

Here is how I work around this beautiful tree to maintain a flourishing garden and have my walnuts, too.

First, 

I found out what is very tolerant and very intolerant of juglone. Several Cooperative Extension Agencies have put out lists of tolerant and intolerant plants – some of these lists contradict each other, so cross comparison is helpful. I specifically looked for the plant families I already knew I wanted to grow – all of the common garden veggies as well as berry bushes. I also kept an eye out for crops that I would be open to growing.

After that, 

I listed out my desired tolerant and intolerant crops/plants and wrote out their habit needs. Here is an abbreviated version of those lists:

Tolerant

Corn – full sun

Squash – full sun

Filberts – partial sun

Currants – partial shade, not heat tolerant

Intolerant

Tomatoes – full sun

Peppers – full sun

Blackberries – partial shade

Next, 

I checked my garden planning maps to determine the best locations for each crop based on these needs. My annual veggie garden is located in the only patch of full sun during the summertime – which, consequently keeps it out from under the walnut tree’s “deadly” dripline. In that space, I can rotate my crops however I like. For my currants, I planted them under the northern canopy of my tree so they get dappled shade all summer and are protected from the worst of our heat. So far, they LOVE it. The filberts and blackberries are going in this spring. The filberts will be on our northern fence line, partially under the walnut canopy and the blackberries will be on our southwestern corner – as far away as possible from the walnut.

Finally, 

I looked into ways to mitigate black walnut toxicity – and from all of my readings, it appears that it only becomes overly toxic when there conditions of competition; not enough water and/or not enough organic matter/nutrients. And, while juglone is not water soluble, it is “compostable” meaning it will breakdown readily. In the right conditions, it can be gone in 6-9 months. However, the highest concentrations of juglone are excreted by the tree’s roots – and as our soil is solid clay over bedrock, it is not likely to leave our soil on its own quickly.

Taking all of that information into account, we created raised beds for our garden (something we were planning to do anyway) and I brought in as much free organic matter as I could – close to 50 gallons of coffee grounds from a local coffee shop, 2 loads of chips from a local arborist, our own steady stream of kitchen scrap compost, all of our neighbor’s maple leaves, etc. During the growing season, I helped the garden retain even moisture by mulching with grass clippings (our neighbor has a lawn service, so clippings were easy to come by).

At the end of our first season gardening around a black walnut tree, we were able to enjoy a full garden with all our favorite annual veggies. Not a single plant showed any sign of “black walnut toxicity.” As we continue to homestead with this beautiful tree, I hope to test the tolerance levels of different plants myself and experiment with composting walnut leaves and unusable nuts. I’ll be sure to write up what we learn!

Half of this year's nut harvest, waiting to be shelled

Thanks for reading,

Susan

P.S. It’s worth noting that black walnut trees need a cross pollinator – our neighbors to the south have a fully mature walnut tree in the center of their yard.

Taylor loves laying under the tree and staring at the leaves. Just watch out for falling nuts!