Walnut trees are common in many landscapes, valued for their shade and nuts. However, they also generate significant droppings. Understanding their nature and timing helps property owners manage them and mitigate potential issues. This article explores the types of walnut tree droppings, the problems they create, and practical management strategies.
Understanding Walnut Tree Droppings
Walnut trees shed various materials throughout the year, following distinct seasonal patterns. The most noticeable droppings are the nuts, encased in green outer husks. These fall from late summer through early fall (August to November) as they mature. Husks often darken, soften, and sometimes split upon hitting the ground.
As autumn progresses, leaves change color and fall. Smaller branches and twigs may also drop periodically, especially during windy conditions or after storms. Walnut trees can also produce sap, though this is less of a concern than nuts and leaves.
Potential Issues from Walnut Droppings
Walnut tree droppings present several challenges. A primary concern is juglone, a natural chemical produced by walnut trees, especially black walnuts, in various parts of the tree. This chemical has allelopathic properties, inhibiting growth or causing death in sensitive plants. Affected plants may show stunted growth, yellowing leaves, or decline. Juglone concentration is highest beneath the tree’s canopy, but its effects can extend 50 to 80 feet from a mature tree.
Beyond juglone, green husks contain a strong dye that stains concrete, driveways, patios, and clothing. These stains are difficult to remove. Fallen nuts pose a physical hazard, creating a tripping risk and slips, especially when wet. They can also be noisy and distracting for vehicles.
Walnut trees and their droppings also attract pests. Squirrels are drawn to the nuts, often tearing open husks and scattering debris. Insect pests include codling moths, walnut husk flies, and various aphids and caterpillars. Codling moth larvae damage nuts, while walnut husk flies lay eggs in ripening husks, leading to larval feeding that ruins nuts and stains shells. Aphids cause leaf distortion and produce honeydew, which can lead to sooty mold growth.
For animals, particularly dogs, ingesting moldy walnuts can be dangerous due to the mycotoxin Penitrem A, causing neurological symptoms like tremors and seizures. Black walnut wood shavings have also been linked to laminitis in horses.
Effective Management and Cleanup
Managing walnut tree droppings involves regular cleanup and strategic preventative measures. Consistent raking or sweeping effectively removes fallen nuts, husks, and leaves. Tools like nut gatherers make collecting nuts less strenuous and more efficient. Prompt removal, especially for nuts, minimizes staining and prevents mold development.
Safe disposal of juglone-laden materials prevents soil contamination. Juglone breaks down quickly when exposed to air, water, and microbes, but can persist in poorly drained soils. Dispose of walnut debris, particularly husks and leaves, away from sensitive plants.
Composting black walnut materials is possible with careful management. A hot composting process (above 140°F/60°C) or vermicomposting effectively breaks down juglone. Create a separate compost pile for walnut debris to avoid contaminating compost for juglone-sensitive areas. Fully composted walnut material can then be used where juglone-tolerant plants are grown.
Protecting vulnerable areas from juglone requires thoughtful planning. Create barrier zones, such as raised garden beds lined with weed barrier fabric or stone, to limit root contact with juglone-containing soil. Fill these beds with fresh, juglone-free soil. Selecting juglone-tolerant plants for areas near walnut trees is a straightforward way to avoid problems. Many perennials, shrubs, and some trees tolerate juglone, including:
Asters
Coneflowers
Hostas
Ferns
Hydrangeas (smooth varieties)
Arborvitae
Some maples
Conversely, sensitive plants like tomatoes, peppers, potatoes, and certain azaleas should be planted well outside the walnut tree’s root zone, ideally 50 to 60 feet away. Improving soil drainage and aeration also helps reduce juglone’s impact, as it breaks down more quickly in well-drained conditions.