November 30, 2013
1 - Most fallen tree leaves can be safely rototilled into your garden in the fall or composted.
Yard and Garden November 30, 2013
I have a lot of leaves that have fallen in my backyard. Most came from a neighbor's tree, but some are from fruit trees in my yard. Can I rototill them into my garden now?
In most cases the answer is yes. Most tree leaves rototilled into the garden in the fall will decompose and improve the soil as they compost in place. They will release some nutrients into the soil and increase the soil's ability to hold both water and nutrients for the garden plants next year. If you want to add manure to your garden, fall is a good time to add it as another soil amendment. Rototilling manure into the garden with the leaves will enhance the decomposition of the leaves and result in better plant growth next year.
The leaves may also be composted in a compost pile or compost bin to be applied to the soil next year as you plant your garden. Once again, manure can be composted with the leaves and will enhance the rate of compost formation. You can also add kitchen wastes throughout the winter and further increase the production of compost for the spring garden. As you add vegetable kitchen wastes to the compost, you can also add water. Water is often a limiting factor in composting in New Mexico. To further enhance the benefits of kitchen wastes, grind or puree them in a blender (preferably on used specifically for this purpose for sanitation reasons). By grinding the kitchen wastes, you will speed decomposition and allow the wastes to coat larger particles of leaves, twigs, or other material in the compost. This will encourage more rapid microbial decomposition of the material in the compost. Remember to turn the compost periodically during the winter to keep it from becoming soggy in the center and dry on the outside.
Your leaves can also be used as mulch in areas where the New Mexico winds will not blow them away. Mulch will help conserve moisture around fruit trees and shrubs, moderate changes in soil temperatures, and reduce weed growth.
Something to consider when using fallen leaves in your garden is the fact that some species of trees produce harmful compounds to interfere with the growth of competing vegetation. Black walnut and tree of heaven are examples of trees that produce these "allelopathic" compounds. However, when these leaves are properly composted, the harmful compounds are eliminated or greatly reduced. If the leaves are used as mulch, the chemical may persist to cause problems. Composting by rototilling into the garden may not reduce harmful compounds as well, but if the leaves you are using have no harmful allelopathic compounds, then there is no concern.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!