Walnut - Wilson's wonder

All the excess rain over the last few months killed my ‘Wilson’s Wonder’ walnut. I’m still grieving. But I know why – it was how I heaped up the mulch. It led to too much water banking up around the roots. Apparently - according to Google - walnuts hate this. In a drought situation such as we have been having over the last 10 years this way of mulching is fine however, not with the levels of water this year.

The tree was planted in June 2009. It was purchased grown from a seedling. The disadvantage of seeding walnuts are that they are variable - some produce very good nuts, some produce rather poor nuts. This tree produced several nuts in its first season. However, the Cockies ate all of them.

The advantage of growing seedling stock over graft stock is that often the root stock used for grafting is black walnut. The roots of black walnuts have consequences for plants grown in its vicinity.

The Black Walnut produces Juglone in its leaves and roots. Many plants are susceptible to Juglone, for example: rhubarb, tomatoes, blueberries and azaleas. Other trees closely related to black walnut also produce juglone, including butternut, English walnut, pecan, shagbark hickory, and bitternut hickory. However, all produce such limited quantities compared to the black walnut that toxicity to other plants is rarely observed.

Leaves that fall from walnut trees, as well as the husks, can also toxic to other plants, so it is recommended not to include them in general composting. The English walnut in this garden was planted near camellias and a large established pin oak. I could find no reference, however, to camellias being sensitive to juglone nor pin oak. You can remedy some of the build up of toxins by improving the soil around the tree. I have added top soil around the tree for this purpose and planted bulbs under the tree to create a mirco environment. Bulbs are not susceptible to walnut toxins.

Walnuts are suited to deep fertile soil and need a minimum of five metre of distance from other plants and houses. Our walnut tree was initially planted too close to the house, only about two meters from the edge. I dug it up one month later and transplanted it closer to the road about five meters away from the house.

Walnut trees are late to leaf in spring and among the first deciduous trees to lose their foliage in the autumn. The nuts ripen in late autumn and drop from the trees around the time of the first frost.

I didn’t know any of these companion planting issues before I purchased the walnut and on doing the research became attached to it. I won’t purchase a replacement though – they are just too big for a suburban block - particularly when I am reliant on full sun for all my other plants. Walnuts do not respond well for pruning!