Soil Requirements for Brassica Vegetables
Broccoli, cabbage, cauliflower and brussels sprouts are just a few members of the brassica vegetable family. These plants grow during the cool season, thriving from fall through spring in mild U.S. Department of Agriculture hardiness zones 9 and 10 or growing as spring or fall plants in colder areas. Good soil that supplies the nutrients and moisture necessary further ensures the brassicas grow and produce well during the growing season.
Brassica plants require soil rich in organic matter. These rich soil types typically have a dark color and moist, crumbly texture. The soil pH, which determines the acidity of the soil, also affects plant growth. Brassica plants need a pH between 5.5 and 6.5. Most established garden beds fall within this range. A soil test verifies the pH and provides a guide for amending the soil to alter the pH into the necessary range when necessary. Tests are available for purchase from garden centers or county extension offices.
Water and Drainage
Moist soils that drain well so they don't become soggy supply optimum conditions for brassica crops. A soil high in organic matter typically drains well unless the garden bed is in a low spot where water collects. Test drainage by digging a 12-inch hole in the proposed bed and filling it with water. If the water drains within two or three hours, the bed supplies proper drainage. If standing water remains after four or five hours, the bed has poor drainage and requires amending or relocating.
Even nutrient-rich beds require fertilization to replenish the nutrients for a brassica plants. A soil test can provide a guide for the amount of fertilizer needed in your garden bed. Generally, 1 pound of an 8-16-16 analysis fertilizer applied to 50 square feet of bed prior to planting supplies sufficient nutrients if a soil test isn't performed. Although not necessary, a 20-20-20 blend starter fertilizer can give the crops an initial boost to encourage quick rooting at transplant time.
Soil Improvement Tips
Improving the soil allows you to grow brassica plants in less-than-optimum locations. Working a 1- to 2-inch layer of compost into the top 6 inches of soil improves soil quality and drainage in denser soils. Agricultural limestone amendments increase soil pH, while sulfur lowers pH. A raised bed can allow you to grow brassicas if you don't have a garden bed with suitable soil. Fill a 12-inch raised bed with a quality soil that has the proper pH, then add fertilizer as necessary. The raised bed improves drainage and aeration by raising the plant's root zone above the poor drainage area.
Jenny Harrington has been a freelance writer since 2006. Her published articles have appeared in various print and online publications. Previously, she owned her own business, selling handmade items online, wholesale and at crafts fairs. Harrington's specialties include small business information, crafting, decorating and gardening.