Master Gardeners agree that soil should not be left uncovered. Bare soil will dry out and blow away, so plant something green to protect soil from dehydration and erosion. Uncovered soil will soon display a blanket of weeds. No gardener wants to spend time in early spring removing weeds before planting. Unplanted soil has no way to obtain nutrients for next year’s crop. Think about planting a cover crop that will provide “green manure” in the spring to replenish your soil.
In rural Gloucester County, we often see winter fields planted in cover crops like red clover. In the spring the cover crop is mowed and either tilled into the soil or left on the surface to decompose. Either method will convert the cover crop into organic matter that will add nutrients to the soil.
Healthy soil produces vigorous fruit, vegetables, and flowers. VCE Publication CSES-132P “The Soil and Me: A Perspective on Soil Health” describes the four necessary components of healthy soil: water (25%), air (25%), mineral particles (45%), and organic material (5%), which consists of humus, organisms, and plant roots.
Planting a cover crop or “green manure” is one way to increase your soil’s ability to hold nutrients. A cover crop is tilled into the soil before it reaches maturity and slowly releases nutrients like nitrogen (N), phosphorus (P), and potassium (K) as the plants decay.
“All very well for farmers,” you say, “but I just have a small vegetable garden with a few rows. Will a cover crop work for me?”
Yes, it will. I heard about planting a cover crop in a family garden from fellow Gloucester Master Gardener Melanie Storrs. Last fall, Melanie planted red clover and rapeseed, which bears yellow flowers, in her cleared vegetable beds. In the spring, she had a beautiful display of red and yellow blossoms that attracted early bees and butterflies. In fact, Melanie said she hated to cut down the plants and deprive her visitors of pollen and nectar.
The two primary groups of cover crops are legumes and non-legumes. Leguminous plants, like various clover species and vetch, work symbiotically with specific bacteria to “fix” nitrogen gas in the atmosphere into soil nitrogen that is available for the plants to use. If the primary goal is to increase nitrogen in the soil, select a legume like red or crimson clover as a cover crop, and inoculate legume seeds with rhizobacterium at planting time to maximize nitrogen fixation. Plant red clover about 4 weeks prior to the first frost, which is Oct. 25 to Nov. 5 in Gloucester. See VCE Publication 2906 1374 “The Organic Way—Selecting Green Manure Crops for Soil Fertility” for other options.
Red clover (Trifolium pratense), a short-lived perennial, will perform well in raised beds in average soil with good drainage and a pH of 6-7. Follow supplier’s directions for seed amounts and planting. In the spring, you will be rewarded with multiple 4 to 8-inch-high plants with pretty pink-purple blooms.
Crimson or crimson red clover (Trifolium incarnatum) is a winter or summer annual, taller than T. pratense at 8 to 20 inches with longer, brighter-red flowerheads and planting requirements similar to red clover. Crimson clover is not reliably heat and drought-tolerant, which should not be a problem in winter.
Non-legume cover crops include grains like oats and rye and brassica crops, such rapeseed and mustard. Rape (Brassica napus) is a cool season annual with large, dark-green leaves and bright yellow flowers in spring. Rape grows well in full sun in soil with a pH of 5.5-8.5 and reaches a height of 3 to 5 feet. A cultivar (Brassica rapa) is the source of canola oil.
Remove all cover crops while plants are flowering at 50% to 80% to prevent seed drop into the soil.
Clemson Cooperative Extension Factsheet HGIC 1252 “Cover Crops” provides general information and VCE Publication “Cover Crop Performance Evaluation and Controlled Studies” discusses the 18 species that were studied.
Plant Extravaganza
A sure sign of fall on the Middle Peninsula is the Gloucester Extension Master Gardeners’ Plant Extravaganza. Our annual plant sale will be held on Friday from 4 p.m. to 6 p.m. and Saturday from 8 a.m. to 2 p.m. at the Moose Lodge 886 Family Center on Route 17. Fall is the time to plant perennials, native plants, trees, and shrubs. We will have herbs, houseplants, and gently used tools and garden books, too. Don’t miss out on some great bargains! All proceeds will benefit the Gloucester Extension Master Gardeners Scholarship Fund and the 4-H Camp Fund.