Extension News

Get on the “Cole” Train

Note to media editors: This is the Garden Column for the week of March 17, 2006.


By Katie Duttweiler

Plant Pathologist

Iowa State University Extension


My favorite St. Paddy’s Day tradition is cooking up a pot of corned beef and cabbage. When I was a kid, this was the only way my mother could trick me into eating cabbage. Through the years, I have grown to love cabbage along with many of the other cole crops. Cole crop is a term used for vegetables in the Brassicaceae family (mustard family) including kale, turnips, collards, cabbage and cauliflower among others. 


Botanically speaking, cole crops are very closely related. For example, broccoli, Brussels sprouts, cabbage, cauliflower, kale and kohlrabi all belong to the same species, Brassica oleracea. Interestingly, the portion of the plant harvested for each cole crop varies. We harvest the thick stem and flower of broccoli, the axillary buds of Brussels sprouts, the terminal bud of cabbage, the flower of cauliflower (called a curd), the leaves of kale, and the swollen stem of kohlrabi. While the nutritional content varies for each vegetable, all are high in vitamin C and dietary fiber. Four of my favorite cole crops, broccoli, Brussels sprouts, cabbage and cauliflower, are a fun addition to any Iowan home garden.


Broccoli, cabbage and cauliflower are cool-weather vegetables which grow well in both spring and fall seasons. Brussels sprouts are also cool-weather vegetables but perform best in the longer fall season. The fall season also provides colder temperatures (and even light frosts) during the end of the growing season that enhances Brussels sprout flavor. While ideal growing temperature ranges from 60 to 70 degrees F, the vegetables are tolerant to light frost. 


Spring crops are established by planting transplants in early to mid April. You can grow your own transplants by starting seeds indoors in early to mid March. Before planting, transplants grown from seed must be hardened by gradual exposure to the outdoors  Fall crops can be started either by direct seeding in early July or by transplanting in late July/early August. Space plants so that there is 18 to 24 inches between plants and 24 to 30 inches between rows. 


The planting location should be in full sun and have slightly acidic to neutral (pH 6-7), well-drained soil  If the soil fertility is questionable, fertilizer (10-10-10) can be applied before planting by incorporating one to two pounds per 100 square feet into the soil. Another option is to apply a side-dressing of fertilizer mid-season. 


Soil moisture must be maintained throughout the growing season to ensure good crop yield. These crops require one inch of water per week.  Irrigation is required if Mother Nature does not sufficiently maintain soil moisture. If weeds appear, they should be carefully removed as to not disturb the shallow root system of the crops. Diseases are best controlled by crop rotation in which a specific garden space is occupied with a cole crop only once every four years. Insect pests, such as cabbageworms (which eat large holes in the leaves), can be controlled by biological or chemical pesticides. 


The harvesting process will vary depending on which crop you are growing. Broccoli is ready to harvest after 50 to 65 days.  Brussels sprouts mature in 80 to 110 days. Early-season cabbage cultivars take 50 to 60 days to mature while late-season cultivars can take 100 days or more. Early-season cauliflower cultivars require 50 to 55 days to mature while late-season cultivars can require 75 to 80 days. 


Broccoli and cauliflower are ready to harvest when the heads are six to eight inches across. Broccoli must be harvested before buds open and yellow flowers appear. Cabbages are ready to harvest when the heads are firm and solid. Cabbages must be harvested promptly as overmaturity causes the heads to split. Brussels sprouts are ready to harvest when the sprouts are firm and 1 to 1.5 inches in diameter.


For more information about growing these vegetables, consult Cole Crops (PM 1896) Iowa State University Extension, available at ISU Extension County Offices or through ISU Extension Distribution online store at www.extension.iastate.edu/store/ or by calling (515) 294-5247.



Contacts :
Katie Duttweiler, Plant Pathology, kduttweil@iastate.edu, (515) 294-0589

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

There are no photos for this week's column.