Test your knowledge about black walnuts by answering true or false to the following questions.
1. Nothing grows under black walnut trees.
2. You musn't plant anything edible near black walnut trees.
3. The juglone poison from walnut roots spreads with watering.
4. The nuts from black walnut trees are edible.
5. The walnut is a good tree for a slope.
6. The name walnut refers to the hardness of the outer shell.
7. Both black walnut and white walnut are native to southern Ontario.
8. You can’t grow black walnut any further north than Toronto.
9. If you have a black walnut tree removed you should use it for mulch.
10. The English walnut is not native to England.
1. False. Black walnut has received a bad rap because the leaves and wood of the tree contain juglone, a substance that is poisonous to some plants. Juglone is most concentrated in the roots and it seeps into the soil. Tomatoes and potatoes will not survive planted near a black walnut, nor will birch, hydrangea, Asiatic lilies or peonies. However, many plants are unaffected by juglne.
2. False. There are several garden edibles unaffected by juglone, including squash, corn, beans and carrots, but cabbage, eggplants, peppers, tomatoes and potatoes will die within about 80 feet of the trunk of a mature black walnut, though.
3. False. Juglone isn’t very watersoluble so it doesn’t spread all that far from the roots of the walnut tree. The roots, however, spread fairly far, and debris from the tree (leaves, nut husks and twigs) can affect the soil around where it falls. Juglone can continue to leech into the soil even after a tree has been removed as the dead roots decompose.
4. True. Black walnut is not the same as the Persian walnuts we buy in the store, but it is edible and, from what I’ve read, has good flavour. It is very difficult to extract from the tough shell, though, which is why it isn’t available commercially.
5. True. Walnuts’ deep and widereaching roots make them a good slope stabilizer.
6. False. Armed only with a dimestore nutcracker, it may seem like the wall of a walnut is impenetrable; the name, however, comes from the old English for foreign nut because the nuts came from Italy or further abroad. The Latin name for the genus, Juglans, means Jove’s nut— the sweet meat was considered a nut fit for the king of gods.
7. True. The white walnut is better known as butternut. These superb trees are under threat of extinction from a fungus that causes canker. It’s estimated that 90 percent of North American butternuts have the fungus. Butternuts in groves have a greater tendency to the disease than those standing alone in a back yard.
8. False. There is a strain of black walnut hardy to Zone 3—that includes all the more populous parts of Ontario and also Alberta.
9. False. Good heavens, no! For one thing, with several plants susceptible to poisoning from the juglone in the wood and bark, black walnut makes a lousy mulch. For another, the timber from a mature black walnut can make the felled tree worth thousands of dollars. The wood is highly prized for its dark colour, hardness and tight grain.
10. True. The Persian walnut ( Juglans regal) is sometimes called English though its native habitat extends from the Balkans through southwest China. A couple of centuries ago, Persian walnut commerce was widely controlled by English merchant marines.
8-10 correct: Sometimes you feel like a nut.
5-7 correct: Sometimes you don’t.
Fewer than 5 correct: Your head is a nut-free zone.