BREEDING, CULTIVARS, ROOTSTOCKS, & GERMPLASM RESOURCES HORTSCIENCE 31(7):1210–1214. 1996. 3) determine if any genotypes attain market- able size under winter conditions before bolt- Importance of Collard and Kale ing. Genotype for Winter Production in Materials and Methods Collard entries included the F1 hybrid cul- Southeastern United States tivars ‘Blue Max’, ‘Flash’, ‘Top Bunch’, and ‘Heavicrop’, and the OP cultivars ‘Vates’, M.W. Farnham1 ‘Champion’, ‘Georgia’, ‘Green Glaze’, and ‘Morris Heading’. In addition to the cultivars, U.S. Department of Agriculture, Agricultural Research Service, U.S. Vegetable four OP collard landraces were evaluated and Laboratory, 2875 Savannah Highway, Charleston, SC 29414-5334 designated as G. Summersett, J.Hope, Mesic Zero, and G. Simpson. Kale entries included J.T. Garrett2 the F1 hybrid cultivars ‘Blue Armor’ and ‘Blue Clemson University, PeeDee Research and Education Center, Florence, Knight’, and five OP cultivars, ‘Improved SC 29501 Dwarf Siberian’, ‘Premier’, ‘Vates’, ‘Squire’ (also designated ‘Squire 88’), and ‘Dwarf Blue Additional index words. cole crops, Brassica oleracea L., Acephala Group, leafy greens, Scotch’. Seed for all cultivars was obtained vernalization, bolting from commercial sources. OP landraces were obtained by M.W.F. from southeastern grow- Abstract. Winter production of collard and kale (Brassica oleracea L. Acephala Group) in ers or gardeners that maintained seedstocks of the southeastern United States is limited by the tendency of these leafy green vegetables to these populations. In addition to ‘Squire 88’, bolt following vernalization. Collard and kale cultivars, landraces, and breeding lines were two other ‘Squire’ populations, ‘Squire 90’ tested in four winter environments from 1992 to 1995 to determine differences among all and ‘Squire 92’, were obtained from E.A. included entries for winter production and tendency to bolt in a cold season environment. Borchers, Hampton Road Agricultural Ex- Essentially all entries survived the conditions of four winter environments. However, periment Station, Virginia Beach, Va. The whether an entry reached harvest size depended on its date of 50% bolting. Collard three ‘Squire’ populations represent C , C , typically bolted earlier than kale. Most kale entries reached a marketable size before 0 1 and C populations resulting from two cycles bolting, while only the collard cultivars ‘Blue Max’ and ‘Champion’ and landraces G. 2 of recurrent selection for delayed bolting (also Summersett and Mesic Zero consistently did the same. Several entries, for example, termed long-standing phenotype). An OP ‘Squire’ kale and G. Summersett collard, usually did not bolt. Results of this research breeding population of kale, Red Green Glaze, indicate that significant genetic control of the long-standing (delayed bolting) phenotype obtained from E.A. Borchers, was also in- is present in collard and kale. Successful winter production of these cole crops can be better cluded. ensured by using a long-standing genotype. Collard and kale entries were seeded in 150-cell seedling trays during Oct. 1992, 1993, Collard and kale are important leafy green month-old collard for 4–5 weeks at 5–7C was and 1994 and grown in a heated greenhouse vegetables grown in the southeastern United the critical exposure needed to vernalize plants for ≈4 to 6 weeks. One week before planting, States. Growers in this region wish to produce and induce bolting. These authors used the transplants were set outdoors to condition them collard and kale year round, exploiting sum- cultivar ‘Georgia’ in one study and ‘Vates’ in to cool weather before transplanting. All seed- mer and winter, as well as the more reliable fall another and made no direct comparison be- lings were at a three- to four-leaf stage when and spring environments. The greatest limita- tween the two cultivars for responses to cold transplanted. In 1992, seedlings were trans- tion to winter production of these greens is treatment. planted to the field at Florence, S.C., on 6 bolting before reaching marketable size. Low Two open-pollinated (OP) cultivars of kale, Nov., and at Charleston, S.C., on 26 Nov. In temperature–induced vernalization causes pre- ‘Squire’ and ‘Premier’, were developed by 1993, seedlings were transplanted on 6 Dec. at mature bolting (Parham and Moore, 1959) and mass selection of plants from ‘Vates’ kale and Charleston, and in 1994, on 1 Dec. Soil type at makes the collard and kale crops unmarket- ‘Improved Dwarf Siberian’, respectively Florence was a Norfolk loamy sand (structure- able. Due to the propensity of collard and kale (Borchers 1990; Borchers and Taylor, 1983). less, fine-loamy, siliceous, thermic, typic to bolt during winter, late fall plantings of The new cultivars were developed by select- Kandiudult) and at Charleston a Yonges loamy these crops are not usually recommended in ing and intermating plants from the original sand (fine loamy mixed, thermic Albaqualfs). southeastern states (Dufault et al., 1992). populations that were slow to bolt following The design of all field studies was a random- Cultivated forms of B. oleracea undergo a cold treatment. Similarly, the collard cultivar ized complete block with four replications. juvenile stage when low temperatures do not ‘Champion’ was derived as a slow-bolting Entries were randomized within replications induce flowering (Warne, 1961). Following population from ‘Vates’ collard (Borchers and and each experimental plot was a single row of the juvenile stage, plants can then be stimu- Taylor, 1979). ≈40 plants of a given entry. Due to unavailabil- lated to flower by a chilling treatment. Parham Although Borchers and Taylor (1979, 1983) ity of seed of particular entries in certain years, and Moore (1959) found that treatment of 2- and Borchers (1990) demonstrated that the G. Simpson collard and ‘Dwarf Blue Scotch’ time to bolting of collard and kale can be kale were grown at both locations only in altered in populations via selection, they have 1992–93, and ‘Heavicrop’ collard and Red Received for publication 12 Apr. 1996. Accepted presented few data comparing their selections Green Glaze kale were grown only in the for publicaiton 13 July 1996. Mention of a trade- and parental sources or other cultivars. More- 1993–94 and the 1994–95 studies. All cultural mark, proprietary product or vendor does not consti- over, we are unaware of any other information practices (e.g., cultivation, fertilization, and tute a guarantee or warranty of the product by the regarding variation in vernalization require- irrigation) used in the field studies were based U.S. Department of Agriculture and does not imply ment or speed of bolting among collard and on commercial standards for the area (Johnson its approval to the exclusion of other products or kale genotypes, including cultivars or breed- et al., 1987). Daily maximum and minimum vendors that might also be suitable.The cost of ing stocks, that are available in the United air temperatures were recorded throughout the publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, States. Therefore, the objectives of this study course of all field studies. this paper therefore must be hereby marked adver- were to: 1) evaluate various collard and kale The number of leaves per plant was counted tisement solely to indicate this fact. genotypes transplanted in late fall and grown biweekly on a subsample of three flagged 1Research Geneticist. through winter months; 2) determine if collard plants in each plot through January, and then 2Visiting Associate Professor. and kale genotypes differ in bolting speed; and weekly after that until plants were harvested. 1210 HORTSCIENCE, VOL. 31(7), DECEMBER 1996 The 20- to 22-leaf stage was designated as a Table 1. Mean maximum and minimum daily temperatures (°C) during collard and kale trials at Charleston marketable size. If flagged plants reached this (Chas) and Florence (Flor), S.C. size, they were harvested, and the fresh weight Location and the date of harvest were recorded. Flagged Daily Chas Flor Chas Chas plants bolting before reaching marketable size were harvested and weighed at the date of temperature Season bolting. Plants were designated as bolted when Month parameter 1992–93 1992–93 1993–94 1994–95 z flower buds exserted from the apical leaf whorl November Max. (18) (18) --- --- and became visible without moving leaves to Min. (8) (6) --- --- December Max. 16 13 (14) 17 expose the growing point. As bolting began, Min. 6 2 (2) 8 the number of bolted plants per plot was counted January Max. 17 14 14 15 every 2 to 3 days. Date of 50% bolting was Min. 7 3 3 4 recorded. The study at Florence in 1993 was February Max. 15 14 18 16 terminated on 15 May, and all studies at Min. 6 1 6 4 Charleston were terminated 30 May because March Max. 19 17 23 22 the plants began to deteriorate with the onset Min. 8 4 10 9 of high temperatures. April Max. 22 22 26 26 A “harvest window” was determined and Min. 10 8 13 14 May Max. 28 (29) 27 30 defined as the number of days from the date Min. 17 (16) 16 18 when plants in a plot attained marketable size z to the date 50% of the plants had bolted. If 50% Temperatures in parentheses are monthly averages computed only from days of the respective month the trial was conducted. of the plants in a plot bolted before reaching marketable size, the harvest window equalled zero. For genotypes that did not reach the 50% bolt stage, the harvest window equalled the number of days from the date of attaining marketable size to the date the study was Table 2. Plant weights at marketable size and the number of days from transplanting to harvest for collard terminated. If a genotype did not reach the genotypes grown in winter environments at Charleston (Chas) and Florence (Flor), S.C.