Walnuts are a common tree here in Ontario and include include both black and white walnuts. Hardy to zone 3a, these trees are native to Eastern Canada and grow tall and wide. Their wood is used in a variety of woodworking applications. While they are highly prized as a shade tree, they are often a very poor choice for urban gardens because of their size and interference with other plants.
Walnut trees produce the chemical juglone, which is primarily concentrated in the roots of the tree. Some of it is in the twigs and the leaves, but the majority of it is found in the soil, even up to 80 feet beyond the drip line of the tree. Juglone interferes with the respiratory mechanism of many plants and causes stunted growth and wilting in many plants including tomatoes and peppers.
Despite their challenges, many gardeners still want garden and sometimes being near a walnut tree is the only option. Here’s how you can make the most gardening near one:
1. Enjoy the Nuts
Most trees should be fairly mature and producing a good quantity of walnuts. It is quite a bit of work to harvest and process the nuts, but it can be rewarding. You must first remove the outer husk while it is still green. Then the inner nuts need to be cured until the hard outer shell dries. Then you can shell them with a nutcracker to get at the tasty walnut nuggets inside.
2. Build Raised Beds
If the tree has a tall or thin enough canopy to let a good amount of light through, you can construct raised beds to grow your vegetables in. Ensure there is a landscape fabric and/or plywood barrier between the bottom of the bed and the new soil of the raised bed.
3. Grow Juglone-Tolerant Vegetables
These include beans, beets, carrots, melons, and squash. Be sure you have enough sun for a good crop or look for allotment gardens or neighbours where you won’t have to contend with the walnut tree(s)
For more information on walnuts, please refer to the OMAFRA fact sheet http://www.omafra.gov.on.ca/english/crops/facts/info_walnut_toxicity.htm.
Cover Image by Armin Vogel, used under its Creative Commons license.
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