By Melanie Mathieson
The Gardening Guru
Walnut is unquestionably one of the finest woods in the world as it finishes beautifully, is easy to work, shrinks and swells less than any other wood, and is durable, which is why our forefathers used it lavishly in homes, barns, and fences.
The trees from the hickory and pecans families are botanical first cousins to walnut, and historically have been used in similar manners.
Many people probably do not know that there are quite a few black walnut and butternuts (also known as white walnut) growing in yards in Fort Frances and properties along the Rainy River. It is not intentionally being kept a secret but many gardeners just didn’t know what tree species it was.
When I still lived in Fort Frances, I would receive many calls every year asking for me to come and identify the tree or the nuts, or a problem with plants dying in the garden.
It always was exciting to see the butternut or black walnut surviving and growing into a fairly large shade tree—and even sometimes producing nuts—in our area.
I came across some black walnut trees on a recent trip to Sudbury, which reminded me of the trees in this district so I wanted everyone to know about them.
The black walnut is native to what is known as the Carolinian Forest in southern Ontario, along the shore of Lake Erie and extending into the southern U.S. The butternut has a similar range in the States, but its Canadian range does cover most of southern Ontario and it also can be found in Quebec and the Maritimes.
For us in Zone 4, these species will grow—not to the height of 70 feet with three-foot diameter trunks, but into a nice shade tree eventually reaching around 50 feet and eventually may produce nuts which the squirrels love.
Practically everyone recognizes a walnut tree when the nuts are on it. Its distinct shape, pattern, and the smell of the bark and twigs are hard to miss, including the tree’s deeply-furrowed black bark.
The leaves are large compound leaves (made up of 15-23 leaflets for black walnut and 11-17 for butternut) and when they fall off, large, horse-faced leaf scars on the twigs are left.
In the spring when buds are present, they do not have bud scales. In addition, the pith is chambered, like a honeycomb. This characteristic is obvious on the end grain cuts of its wood and a tell-tale clue when identifying wood furniture.
The walnut pith is brown and is buff-coloured in the butternut.
Both species like fertile soils in mixed hardwood forests, but also will grow well in pastures, meadows, and on slopes. For the yard, they like full sun and fertile soils, so make sure to add lots of compost to the hole.
Ensure to plant a distance from the house as the roots will become large like those of the maple species.
These trees may suffer some winter damage but they are out of their zone, so it is expected.
The walnut has a double value as there is a multi-million dollar market for its nuts. The richly-flavoured nut of the black walnut are those used by bakers, as well as candy and ice cream makers, and available in the grocery stores.
In addition, the hard shells are used as ornaments, and pulverized and then used to drill oil wells, clean jet engines, and to make activated carbon (a type of industrial charcoal used in a variety of ways).
During World War II, for instance, gas mask filters were made from this activated carbon.
Wildlife loves the walnut, too. The nut is enclosed in a solid, non-splitting husk, and is borne on the tree singly or in pairs.
A note of warning to humans: be careful handling the nuts of the black walnut as this husk will emit a brown stain that will stain your hands and, for some people, create a rash. As such, use gloves when handling.
This is where authentic walnut stain (pigment and artist products) comes from.
Be patient if you plant one in your garden as they do not produce nuts until they are more than 10 years old (and maybe older in our zone). But when the first nuts appear, it will be really exciting.
Most members of the walnut family, including black walnut, pecan, and butternut, produce a chemical called “juglone,” which occurs naturally in all parts of these plants.
This juglone can cause toxic reactions with a number of other plant species that grow in their vicinity. Symptoms of walnut toxicity range from stunting of growth to partial or total wilting to death of the affected plant.
The toxic reaction often occurs quickly, where sensitive plants can go from healthy to dead within one or two days. Many alarmed gardeners often believe the cause of wilting is due to fungal or bacterial disease and once wilting begins, the effect cannot be reversed.
This is why I often would receive calls from distressed gardeners.
You still can enjoy a black walnut or butternut, but gardens should be located away from black walnut and butternut trees to prevent damage to susceptible plants.
Where close proximity is unavoidable (i.e., a neighbour’s yard), then raised garden beds can provide some protection from juglone toxicity.
Care must be taken to minimize or prevent walnut tree roots from growing upwards into the raised beds. Underlying a garden with plastic or fabric weed barrier during construction can prevent this.
I really encourage you to try and find a black walnut or butternut seedling at your favourite nursery. If you like to experiment and push the zone, then this is a perfect choice.