Gardens & Conservatory

Gardening Articles

Green Manure Promotes Green Thumb Success


By Tom Brinda and Lynn Kirk, Lewis Ginter Botanical Garden. Reprinted with permission from the Richmond Times-Dispatch.

If you’re new to gardening, the term “green manure” may conjure up unpleasant images. Though it sounds like a strange animal by-product or perhaps the newest eco-friendly soil additive, green manure actually relates to a centuries-old agricultural technique that enhances the soil. Farmers and vegetable gardeners strategically rotate crops following harvest or when soil demonstrates a need for nutrient replenishment. Rather than leaving the land fallow, they plant a “cover crop” of red clover, winter rye, alfalfa or similar plants. This secondary crop provides numerous benefits while it grows, then near maturity it is tilled into the soil as green manure, usually a month before the next planting cycle. The process works just as well in small gardens as large farms.

The time and cost of planting green manure are not only minimal; they are far outweighed by the returns. Acting as nature’s fertilizer, green manure improves soil health by adding or recycling essential nutrients such as nitrogen, phosphorous and calcium. Buckwheat, a summer-grown cover crop with an extensive root system, tends to reach more deeply into the earth to absorb other important nutrients, such as potassium, which normally are not within reach of shorter-rooted crops. Green manure also provides organic matter that later is broken down by microorganisms. Over time this decomposition releases additional nutrients and makes the soil less compact.

Growing a diversity of crops provides another natural benefit: pest control management. Different plantings at various times of year help maintain pest balance and prevent serious outbreaks. Likewise, cover crops attract pollinating insects and provide food for wildlife without seasonal interruption.

During winter, green manure acts as “living mulch” or protective blankets that help prevent soil erosion and retain moisture loss. Since a cover crop competes with weeds for space and light, it helps crowd out unwanted plants by reducing germination and suppressing growth.

As an added bonus, this time of year a field of red clover or a stand of alfalfa enhances the landscape as the grower waits for spring.

Green manure seeds may be purchased in bulk at seed stores or in smaller quantities at full-service garden centers.