Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/1996
Publication Date: N/A
Interpretive Summary: Collard and kale are important leafy-green vegetables grown in the southeastern U.S. These crops are mainly grown in the fall and spring; but, southeastern farmers are increasingly trying to produce these crops in summer and winter. A big problem in trying to produce collard and kale in winter, is that they tend to go to flower in a cold environment. Once they yflower, they lose marketability. The objectives of this research were to see if different varieties of collard and kale would perform differently in winter environments and exhibit different tendencies to flower in the cold. Thirteen collard and 11 kale varieties were tested in winter environments, and results showed that varieties do perform very differently. Certain varieties flowered before reaching a marketable size while others attained a desirable size, and then flowered. The latter varieties are well-suited for winter production. This research shows that farmers can increase their rchances of producing a good, marketable collard or kale crop during winter by choosing a variety best suited for the cold season. By enhancing a farmer's knowledge and ability to produce these crops in winter, these studies ultimately help extend crop production over a greater portion of the year. Thus, the supply of collard and kale available to consumers and an individual farmer's profitability are both increased as a result of nearly year-round marketing.
Technical Abstract: Winter production of collard and kale (Brassica oleracea L. Acephala Group) in the southeastern United States is limited by the tendency of these leafy-green vegetables to prematurely bolt following vernalization. Collard and kale cultivars, landraces and breeding lines were tested in four winter environments in 1992 to 1995 to determine differences for winter production and tendency to bolt in a cold season. Transplants were set in the field during November or December and plant growth was monitored through the spring. When plants reached a marketable size, fresh weights were taken. The date at which 50% of all plants in a plot bolted was also recorded. The number of days from attaining harvest size to the 50% bolt stage (designated the Harvest Window) was also assessed for each entry. Whether an entry reached harvest size depended on its date of 50% bolting. Most kale entries reached a marketable size prior to bolting in most winter renvironments while only the collard cultivars 'Blue Max' and 'Champion' an landraces 'G. Summersett' and 'Mesic Zero' consistently did the same. Several entries, for example 'Squire' kale and 'G. Summersett' collard, usually never bolted. Results of this research indicate that significant genetic control of the delayed-bolting phenotype is present in collard and kale. Successful winter production of these cole crops can be better insured by using a genotype that is slow to bolt.