Issue: August 27
Leaves from healthy plants may be left under plants as a mulch
Q. Should I leave the dead leaves from the daffodils and other dead leaves in my flower beds for mulch? If so, would it be beneficial to put a layer of quality potting soil on top; it seems as if the soil just disappears from my beds.
A. Dead leaves left in the flower bed as a mulch may be helpful. This is the way that plants mulch themselves in nature. Leaves from trees, shrubs, grasses, and other plants fall to the ground and provide mulch. This enriches the soil as nutrients from decomposing dead leaves are released to the plants. They also help moderate soil temperature and conserve moisture. As long as you did not see any signs of disease (powdery mildew, leaf-spot diseases, or other diseases in the leaves left in the garden) you can leave the leaves as mulch. If you had an obvious problem with diseases, it would be best to remove the leaves. You may have seen signs of stress on the leaves from heat, wind, or drought, but these are not a concern. If you have concerns about diseased leaves, common advice is to discard the leaves and do not compost them. Since our soils need the additional organic matter for many garden plants, I often take diseased plants, weeds, and other traditionally non-compostable material, put it into a garbage bag in a sunny location and let the heat from the sun pasteurize them, killing most of the weed seeds and disease organisms. Heat at or above 160 degrees is needed for this, but in our climate, a week in the sealed bag in the sun is enough to pasteurize these materials which can then be put in the compost, or back on the soil as a mulch. If you want to put some potting soil or compost on the soil with the leaves, that is OK. The soil seems to disappear from your flower beds because organic matter continues to decompose and diminish in volume over time. Adding new organic matter in the form of compost, potting soil, or mulch helps restore the volume of the soil.
For more gardening information, visit the NMSU Extension publications World Wide Web site at http://aces.nmsu.edu/pubs/_h.
Send your gardening questions to:
Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd. SW
Los Lunas, NM 87031
Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating.