University of Maryland Extension

September - Soil, Fertilizer, Mulch & Compost Tips

compost in a wheelbarrow

Compost. Photo by Oregon State Extension

(More tips from HGIC)


  • Adding organic matter in the form of composted leaves, composted manure, chopped up spent flowers and vegetable plants, grass clippings, etc. will improve soil structure, increase soil fertility and help you produce healthier plants.

  • Have your soil tested, if you have not had your lawn or garden soil tested for the past 3-4 years. Many plant problems can be solved by correcting soil deficiencies. Refer to our website for information on soil testing.

  • Winter (PDF) cover crops can be planted now on bare garden soil. Sow the following species individually or in a combination: hairy vetch, winter rye, oats, winter wheat. Mix the seeds with soil and broadcast them by hand or use a hand held broadcasting seeder. Gently rake the seeds and walk on the bed to ensure good soil to seed contact. Your cover crop will protect your soil, conserve soil nutrients and add valuable organic matter and nutrients when tilled in next spring.


  • It is still too early to fertilize shade trees, fruit trees or shrubs. Late summer fertilization promotes new growth at a time when perennial plants are beginning to enter dormancy and resulting in increased winter damage. Trees are typically fertilized after they drop their leaves in the fall. Mature shade trees do not typically need to be fertilized at all. They also get some benefit from the fertilizer applied to the lawn.

  • Bluegrass and fescue turf is fertilized in the fall. When fertilizing an established lawn, select lawn fertilizers that contain only nitrogen.

  • To reduce nutrient pollution of groundwater and the Chesapeake Bay, keep fertilizers off hard surfaces like driveways and sidewalks. Use caution when fertilizing areas of your yard that border these hard surfaces.


  • Mulches should be applied only 2-3 inches deep around ornamental plants and kept away from shrub and tree trunks. Mature trees do not benefit from being mulched, except to keep damaging lawn mowers away from the trunks.


  • With fall comes the leaves that drop; they are a valuable resource to gardeners. Add them to your existing compost pile, or start a new one. Strive to incorporate a mixture of green, high nitrogen materials like grass clippings, spent plants and kitchen waste with dry materials high in carbon, like shredded newspaper, straw or shredded leaves.

  • Compost piles should be at least one cubic yard in volume to heat up properly. Finished compost is the very best starter material for a compost pile because it contains nitrogen and a huge number of microbes that help transform organic matter into compost. It is also not necessary to add soil or lime to a compost pile.
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