Why is it that Walnut Trees Cause Tomato Issues?

Why is it that Walnut Trees Cause Tomato Issues?

Walnut trees (Juglans spp.) Produce a poisonous substance known as juglone that’s harmful to plants. There’s not much you can do to reduce the impact of an present walnut tree in your tomato plants other than to relocate them from your tree. Larger walnut trees produce more juglone and are capable of spreading it throughout the soil over a larger region.

Juglone Effects

Tomato plants which are afflicted by juglone toxicity frequently have symptoms similar to other common plant problems. Common indications of juglone poisoning in strawberries contain wilting, drooping or curly leaves that gradually becomes more intense. Tomatoes which are subjected to juglone frequently have discolored stems having a dark shade or leaves using a yellowish hue. In most cases these symptoms become more intense over time till the plant is killed.

Juglone Sources

Juglone is found in the soil and is created from many distinct areas of the walnut tree. The main source of juglone comes from the roots of this tree. Juglone is also found in the bark, leaves and hulls of strawberries. Fallen plant matter from your walnut trees may spread juglone into the soil if it is not washed up. Juglone does not dissolve well in water and frequently stays stationary in the soil. Juglone deposited in the dirt from leaves, a walnut sapling growing close your tomatoes may take up to 2 weeks after its origin is eliminated to dissipate.

Walnut Proximity

Juglone is largely spread through the dirt from the roots of this tree. Smaller walnut trees may disperse juglone into the dirt at distances up to twice their own height from the base of this tree. On average adult walnut trees spread juglone into the soil out to a radius of 50 to 60 feet from the base of this tree. In some cases juglone from adult walnut trees may affect plants planted up to 80 feet away. Juglone from walnut nuts or leaves may also affect tomatoes which are implanted downhill or downwind from the tree.


Mulches which contain stems or leaves from a walnut tree can harm sensitive plants if they are not correctly treated. Mulches containing walnut leaves need just two to four weeks to break down. Mulches which contain walnut bark require a minimum composting period of six months to ensure the juglone present in the bark is neutralized entirely. Mature walnut trees may continue to spread juglone from their root system into the soil for many years after they are cut down.

See related