Black walnuts are taking over my garden

| 31 Dec 2013 | 03:24

Sometimes it is difficult to know whether something is an asset or a liability. This is the case with the black walnut trees that dot our property. As a highly valued hardwood coveted by woodworkers, a mature specimen can fetch thousands of dollars. In fact, recent demand for this beautiful, dark wood is so great in China that it is now profitable to ship locally harvested logs overseas. The nuts are also sought after by epicures and command a considerable price, although I am not convinced that this has as much to do with their flavor as with the fact that they are so difficult to pick. Herbalists have long appreciated black walnut’s curative potency. High in iodine, a tincture made by soaking green walnuts, hull and all, in vodka is said to cure periodontal problems by soothing canker sores, inhibiting cavities as well as enhancing enamel growth in teeth. Taken internally, the diluted tincture has been used to purge intestinal parasites. In cosmetics, the pulverized nutshell is used in facial scrubs.

You would think that I would be happy to have so many black walnuts on our property. Not so. Each fall, while bombarded by falling nuts, we twist our ankles on slippery, stain-saturated hulls. Dented car hoods and two cracked windshields have taught us to park far away from their canopies. I have attempted to make the best of a messy situation by consuming the nuts, sculpting the wood and tinting floors with the penetrating stain that the mature hulls excrete. I dye fibers in brews made with black walnuts soaked in water, which is one of the most permanent natural dyes. As a new apiarist, I am delighted to learn that smoke from burning walnut leaves may curb varroa mite populations in beehives. Even so, it seems that the black walnuts may have the upper hand and are taking over my garden.

To my great dismay, most of my tomatoes collapsed suddenly this past summer, over a period of several days. With healthy leaves, the four-foot tall plants showed no signs of disease as they were coming into bloom. I had planted them in raised beds which five years before had produced prodigious amounts of tomatoes. Since I rotate my crops regularly, I thought nothing of planting tomatoes in these beds again, not realizing that the black walnut tree outside my garden had, in the meantime, doubled in size. Unbeknownst to me, its spreading roots had crept into my garden and under my raised beds. Black walnut trees exude juglone, a toxic substance, through their roots. Certain plants are highly sensitive to juglone and should not be planted within the tree’s root zone, which can span more than 60 feet. These include the nightshade family of tomatoes, eggplants, peppers and potatoes. Asparagus, rhubarb, blueberries, apples and pears are also intolerant of juglone. Symptoms include yellow or brown leaves that are often twisted or deformed. Plants become stunted or wilt suddenly. I suppose that my tomatoes were able to thrive in the raised beds until their roots grew deep and came in contact with the juglone. In the future, I will have to plant other kinds of vegetables that are more tolerant of black walnuts in these beds. Beans, carrots, squash, melons, and alliums, such as onions, scallions, shallots, leeks and garlic, should fare well.