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Plant of the Week: Brassica oleracea Cauliflower

Brassica oleracea Cauliflower -- Cauliflower now can be had in colors such as green or orange. (Image courtesy Gerald Klingaman.)


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We’ve all been admonished to eat our vegetables, and sometimes we even follow that sage advice.  I’m a big fan of most vegetables and especially like cabbage, broccoli, kale and Brussels sprouts, but their pale cousin, cauliflower, has been harder to warm to.  But the world, she is a-changing, and the white curds of cauliflowers are now available in designer shades.

Cauliflower is closely related to broccoli, both being members of the crucifer family and classified as Brassica oleracea Botrytis Group.  All of the crucifers – everything from cabbage to kohlrabi – are native to the Mediterranean region and derived from ancestral wild cabbage that still grows in the region.  Over the past 4,000 years, variants of the wild species have been selected and modified by farmers in what is one of the first examples of extreme genetic modification. 

Like other crucifers, cauliflower is a biennial.  To get it to flower plants must go through a winter with the typical 4-petaled yellow or white flowers produced on elongating shoots in the spring.  However, cauliflower is a more temperamental crucifer than most.  It is the most freeze sensitive of the crucifers and also intolerant of heat and drought.

The edible head (curd) of cauliflower is formed from fused flowers.  White curds are the typical form and have been described in early writings since at least 600 B.C.   The now war-ravage country of Syria was the source of some of the first forms of cauliflower grown in Spain that eventually spread to the rest of Europe. 

Early Italian cauliflower cultivars have included color variants but it was not until 1970 with the chance discovery of an orange-headed mutation in a Canadian cauliflower field that the story of the modern colored forms began.  A sample was collected of the plant, it was propagated and eventually made its way to the National Vegetable Research Center in England.  Researchers there knew of the interest Michael Dickson, a Cornell University crucifer breeder working with cauliflowers, so they sent him samples.  In 1989 Dickson released the orange headed breeding lines to commercial vegetable seed companies.  The orange clone Cheddar was released in 2004. 

Orange cauliflower has a high vitamin A content.  Green cauliflower lines began appearing about 1990 and contain low concentrations of chlorophyll in the curd to produce the green shading.  The purple cauliflowers rely on the anthocyanin pigment found in red cabbage to provide its color.  Cauliflower is low in calories and carbohydrates, making it a substitute for starchy foods such as potatoes, rice and pasta. 

Cauliflower can be grown as a spring or fall crop in Arkansas.  Seeds are started indoors in the winter with the planting date delayed until about two weeks before the anticipated last frost date.  White curded cultivars such as Snowball mature in about 10 weeks, so they should finish before the worst of the summer heat.  Fall crops can be planted in August but careful attention must be paid to watering to assure success.  For best results a uniform moisture and fertility regime must be maintained to assure successful production. 

Some cauliflower clones are said to be “self-blanching,” a reference to the fact that the uppermost leaves curve inward and shield the developing curd from the direct rays of the sun.  For older cultivars blanching is done by tying together the uppermost leaves in a loose bunch when the curd is 2-3 inches across.  This reduces the chance of sunburn and prevents the development of chlorophyll, which can lead to an off taste.  Blanching is more important for the spring crop than the fall crop.

Being a crucifer, cauliflowers are plagued by a number of diseases and insect pests.  The cabbage looper is the most serious insect pest and early infestations can result in serious defoliation, which reduces curd development.  BT, an organic insecticide, has proven effective in controlling this pest.

For more information about horticulture or to see other Plant of the Week columns, visit Extension's Web site, www.uaex.edu, or contact your county extension agent. The Cooperative Extension Service is part of the U of A Division of Agriculture.

 

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