Walnut Extract & Its Effect on Plant Growth

Prevents Respiration

• Juglone has been shown to inhibit respiration in plants. Sensitive plants cannot exchange carbon dioxide and oxygen properly. In effect, they cannot breathe.

Symptoms

• Susceptible plants grown near black walnut trees can show symptoms of walnut extract or juglone toxicity. They will probably be stunted in their growth. They may also look like they're wilting; once they start wilting there is nothing that can be done. They will eventually die.

Susceptible Plants

• Certain vegetables and ornamental flowers are susceptible to juglone toxicity of black walnut. Some of them are: apples, tomatoes, potatoes, alfalfa, blueberries, asparagus, cabbage, azaleas and chrysanthemums.

Tolerant Plants

• Some vegetables that are tolerant of juglone and can be grown near black walnut trees include beans, beets and carrots. Other tolerant plants include bugleweed, anemone and clematis.

Young Walnut Trees

• Apparently, all plants can grow beside young walnut trees with no adverse effects on plant growth. The walnut trees only start producing juglone when they are about 7 or 8 years of age.

Soil Drainage

• Excellent soil drainage is one way to counteract the effects of juglone toxicity. Also, as long as the roots of the walnut tree do not come into contact with susceptible plants, these plants stand a chance of growing fairly normally.