Why doesn’t anything grow properly around the walnut tree? The answer is juglone! This substance protects the tree from pests, but at the same time creates an invisible circle of death around it for sensitive plants. But there are species that can resist juglone.
Ominous Nutcracker
When we think of a walnut tree, most of us imagine a tall and powerful tree with a wide crown. Hard wood and tasty fruit that you can only get to by dyeing your fingers brown. It is a tree that has belonged to the Czech countryside since time immemorial and it used to be a tradition that it has dark abilities and brings bad luck. Everyone who has a walnut tree in their garden knows that greenery does not thrive near the tree. Perhaps behind the “bad reputation” and gossip is what we know today as juglon.
It can certainly be said that the massive crown shades the surrounding greenery, but that is not the case. The nutcracker plays a much more refined and harsh game with its surroundings. He uses a weapon that is technically called allelopathy.
An invisible poison called juglone
The biggest treasure and curse of the walnut tree is the aforementioned juglone. It is an organic compound that the tree produces in absolutely all its parts. We find it in the roots, in the bark, in the juicy green skins of nuts and most of all in the leaves. It is the perfect protective shield for the nut tree. It protects it from hungry insects and diseases, but at the same time creates a competitive environment that other plants cannot face. Even more nutrients and moisture can fall to the walnut tree.
As leaves fall and begin to decompose in the soil in the fall, or as summer rain washes the drops from the canopy down into the beds, juglone soaks into the soil. For neighboring plants, it is a complete disaster:
- Stop growth: Plants in the vicinity suddenly lose strength, stop breathing and cannot take in nutrients.
- Yellowing and wilting: The leaves of the neighboring bushes begin to turn hopelessly yellow, curl and dry, even if they have enough water.
- A certain end: The more sensitive species literally go away in a few weeks, as if someone had sprayed them with chemicals.
This effect becomes particularly severe in the dry summer months. When there is little water in the soil, juglone does not wash away, but instead concentrates. This creates an invisible circle of death around the walnut tree, which can reliably destroy neighboring beds. Devil’s allelopathy, however, is not only a prerogative of the walnut tree, but also, for example, of the invasive thorn acacia and glandular pajasan.
Who doesn’t survive the nutcracker and who doesn’t mind?
If you have a walnut tree near a fence or vegetable beds, you need to be very careful about what you plant near it. Among the most sensitive victims of juglone are tomatoes, peppers and potatoes. Those next to him suffer almost immediately. You will also fail to grow more exotic species such as rhododendrons, azaleas or lilacs. Even apple and cherry trees do not grow well near the walnut tree.
Fortunately, there are plants that have a “hippo skin” against juglone. If you want to liven up the space under the tree, reach for these durable companions:
- Shade permanents: Ferns, hollyhocks or the grateful periwinkle do nothing for juglone.
- Bulbs: Spring messengers such as daffodils, snowdrops and crocuses bloom before the walnut tree has time to sprout and launch its chemical defenses in the spring.
- Shrubs: Among the woody plants next to it, for example, blackberry or meruzalka thrives without problems.
Where with the leaves so we don’t hurt ourselves?
The biggest dilemma of any walnut tree owner comes with autumn. What to do with that huge pile of fallen leaves? Old gardening wisdom said that compost should not be allowed because it would poison it. The truth is, as always, somewhere in the middle.
Fortunately, juglone can break down due to air, bacteria and time. If you compost walnut leaves separately or mix them with other waste, you have to give it time. It breaks down extremely slowly. But in two years there will be compost from it too. But if you are in a hurry, it is better to take it to the bio-waste or burn it.
But you can also use juglone in a more subtle way. If you keep chickens, use the dry leaves as bedding in the chicken coop. Juglon repels insects and mites. In addition, it also reduces odor. This too is folk wisdom, proven by generations of breeders.
