CRIMSON CLOVER26
Trifolium incarnatum L., family LeguminosaeCrimson clover is an important and colorful winter annual legume in the South and is grown to some extent on the Pacific coast, where winters are mild. It is also grown in some Northern States as a summer annual. Alabama, Georgia, and Tennessee, in that order, were the leading producers of crimson clover seed, but most of it is now produced in Oregon. More than 2.5 million pounds were produced in 1970.
Compared to other clovers, crimson clover is a heavy producer of seed. Yields of 300 to 600 pounds per acre are common, and yields of 1,000 to 1,200 pounds have been obtained (Wheeler and Hill 1957*).
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26 See "Clovers, General."Plant:
Crimson clover grows erect to about 2 feet tall, and is easily recognized by its crimson flowers that are about 2 inches long by 1 inch wide. It resembles red clover, but its leaves have a more rounded tip, and both the stems and leaves have more hair on them than does red clover. It is usually sown and develops a crown of growth in the fall. In the spring, fresh stems form, then terminate in the long, pointed flower head. Flowering in the South occurs in April. The seeds develop, then with the coming of summer weather, the plant dies.
The plant is widely used as forage, pasture, green manure, and an erosion control plant. It has the advantage of producing large quantities of seed that can be, easily harvested and planted without the use of expensive equipment (Hollowell 1938).
Inflorescence:
The 65 to 125 crimson florets that make up the colorful crimson clover head are typically Trifolium and roughly 5/8 inch long by 1/8 inch wide. Weaver and Ford (1953) recorded 96 florets per flower head and estimated roughly 2 million flower heads per acre. Amos (1950) estimated 200 million florets per acre.
Knight and Green (1957) stated that although honey bees are attracted to crimson clover they have difficulty in forcing their mouth parts into the floret. The bee trips the floret whether nectar or pollen is collected. Knight (1969) found that an apetalous male-sterile selection was unattractive to bees.
Girardeau (1958), Lovell (1926), and Pellett (1947*) rated crimson clover high as a honey plant. The quality of honey produced is excellent. Girardeau (1954) stated that when bees forage on crimson clover they do not crowd their broodnest with honey. Girardeau (l 958) observed that bees collected nectar from crimson clover primarily in the mornings and pollen in the afternoons. This is exceptional because most plants that attract bees for pollen do so in the forenoons. The pollen is collected in large amounts and this, also, is unusual for leguminous plants. Girardeau (1958) also noticed that cells filled with crimson clover pollen were scattered throughout the honey storage area instead of being concentrated around the broodnest, and that colonies foraging on this crop swarmed excessively. No reasons were determined for these behaviorial differences.
Pollination Requirements:
The crimson clover floret is self-fertile but is not self-tripping (USDA 1967), therefore pollinating insects are required for profitable seed production (Pieters and Hollowell 1934). The flower is easily tripped. After tripping and release of pressure on the keel petal by the bee, the stamina! column returns to its original position. No data have been obtained on the value of repeated bee visits to a floret. If the floret is pollinated, it withers within a day's time; but if not pollinated, it will remain fresh-looking for about 2 weeks. This characteristic contributes to the flower-garden appearance of a poorly pollinated field and the dull appearance of a well-pollinated field (Knight and Green 1957).
Pollinators:
There seems little doubt that honey bees are the primary pollinators of crimson clover. Knight and Green (1957) stated that wild bees, such as bumble bees, do not pollinate much crimson clover. They accredited wind and rain with 13 to 20 percent of the pollination in the open. Scullen (1956*) observed that the flowers were attractive to bumble bees and some species of wild bees in Oregon, but in general he indicated that they alone were insufficient. Girardeau (1958) found that because of the early flowering of crimson clover in the spring in Georgia, few bees other than honey bees were active in the field. Beckham and Girardeau (1954) reported that about 2 percent of the bees in the field were bumble bees, the rest honey bees.
Weaver and Ford (1953) stated that virtually all of the pollination seemed to have been performed by honey bees. Blake (1955) reported that pods containing seeds and seed yields were always higher near apiaries. Hollowell (1947) stated that bees were effective as tripping agents and in the transfer of pollen from flower to flower, with a consequent increase in the number of seeds per head. Wheeler and Hill (1957*) stated that placing colonies of bees near fields has increased yields in some cases up to 1,000 to 1,200 lb/acre.
The effect of honey bees as pollinators has also been established with cage tests. Amos (1950,1951) obtained only 2.64 g of seed from 50 crimson clover heads caged under 2-, 4-, or 16-mesh per inch screen to exclude various types of bees, but harvested 6.36 g per 50 heads exposed to one colony of honey bees per acre. Scullen (1956*) obtained five seeds per head excluded from bees, but 69 seeds per head available to bees. Beckham and Girardeau (1954) harvested 130 lb/acre from caged plots but 491 lb/acre from open fields supplied with one colony per acre. Blake (1958) obtained 1,019 lb/acre with three colonies per acre and best agronomic practices, a gain of more than 800 pounds over production where bees were excluded. Killinger and Haynie (1952) harvested only 3 lb/acre in cages where bees were excluded, 64 lb/acre from cages with bees, and 105 lb/acre from open plots. Weaver and Ford (1953) harvested 59 lb/acre from cages where bees were excluded, 233 lb/acre from bee cages, and 297 lb/acre in open plots. (Eight colonies of bees were one-half mile from the 4-acre experimental plot.)
Johnson and Nettles (1953) obtained 37 pounds of seed per acre in caged plots but 375 lb/acre in the open field where there were 2.5 colonies of honey bees per acre. Vansell27 reported that he obtained 5.08 seeds per head on caged crimson clover plots in Oregon and 69.2 seeds per head in the open field. He stated that a 144-acre field in Hanford, Calif., supplied with three colonies of honey bees per acre produced 1,100 pounds of seed per acre.
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27 VANSELL, G. H. POLLINATION STUDIES. U.S. Dept. Agr., Pacific States Bee Cult. Field Lab., Davis, Calif., First Quart. Rpt. of Prog., p. 17. 1952. [Processed.]Pollination Recommendations and Practices:
The need for honey bees as pollinators in the production of crimson clover seed is firmly established. The number of bees required is less firm. In Texas, Weaver and Ford (1953) calculated that one colony of honey bees per acre should be sufficient to saturate any field of crimson clover, providing there was not too much competition from other sources of pollen and nectar. Pedersen et al. (1961) and Girardeau (1958) also recommended one colony per acre. Killinger and Haynie (1952) recommended one colony per acre, but they stated that some increase in seed production was obtained with up to five colonies per acre. Blake (1958) recommended two colonies per acre in Alabama, and, when three colonies per acre were used, the exceptionally good yield of 1,019 lb/acre was obtained. Hollowell and Knight (1962) recommended the placement of the colonies of honey bees in or adjacent to the field, and they stated that, with good clover stands and good pollination, yields of 1,000 to 1,200 pounds of seed per acre could be obtained.
Weaver and Ford (1953) stated, "The clover itself gives a reliable indication of whether there are adequate numbers of pollinating insects in the field. When the blossoms are not pollinated they remain open for about 2 weeks before they wither. Blossoms which are pollinated, however, wither within a day. In the cages from which all insects are excluded, the blossoms open in successive whorls from the bottom, and remain open until the entire flower head is a solid mass of beautiful open florets. When adequate pollinating insects are present, however, there is a narrow whorl of open blossoms with buds above and withered flowers below. A field with some pollinating insects, but in inadequate numbers, has an "intermediate, or rather spotted appearance."
Knight and Green (1957) stated that close proximity of a field to honey bee colonies does not guarantee good pollination because of possible competition by other plants. They offered a much better method of estimating pollinator populations - bee visitors on the clover flowers. They believed that from two to three bees per 100 flower heads was an adequate population for good pollination. The counts should be made between 10 a.m. and 3 p.m., on a warm day with the clover in full bloom. They warned that "Since the peak of blooming and pollination is so short, it is often too late to get more bees when their need is discovered and the counts may be of value only for the next year." The grower might be wise to assure himself of a higher bee population in the field before peak bloom to insure adequate pollination at that time. By doing this, his field would never become a flower garden but would yield the maximum crop of seed.
LITERATURE CITED:
AMOS, J. M
1950. PRODUCE MORE CRIMSON CLOVER SEED WITH HONEYBEES. Tenn. Mkt. Bu1.22(11): 6 - 7.____ 1951. THE EFFECT OF HONEYBEES ON THE POLLINATION OF CRIMSON CLOVER. Amer. Bee Jour.91: 331 - 333. 200
BECKHAM, C. M., and GIRARDEAU, J. H., JR.
1954. A STUDY OF HONEYBEES AS POLLINATORS OF CRIMSON CLOVER. Assoc. South. Agr. Workers Proc. 51st Ann. Conv., p. 95.BLAKE, G. H.
1955. CRIMSON CLOVER POLLINATION BY HONEY BEES. Assoc. South. Agr. Workers Proc. 52d Ann. Conv., p. 102.____ 1958. THE INFLUENCE OF HONEY BEES ON THE PRODUCTION OF CRIMSON CLOVER SEED. Jour. Econ. Ent. 51: 523 - 527.
GIRARDEAU, J. H., JR.
1954. RESEEDING CRIMSON CLOVER - AS A MAJOR HONEY PLANT IN SOUTH GEORGIA. (Prelim. Rpt.) Ga. Agr. Expt. Sta. Mimeo Ser. n.s. 1: 1-7.____ 1958. THE MUTUAL VALUE OF CRIMSON CLOVER PLANTINGS AND HONEY BEES FOR SEED AND HONEY PRODUCTION IN SOUTH GEORGIA. Ga. Agr. Expt. Sta. Mimeo Ser. n.s. 63: 1-23.
HOLLOWELL, E. A.
1938. CRIMSON CLOVER. U.S. Dept. Agr. Leaflet 160, 8 pp.____ 1947. CRIMSON CLOVER. U.S. Dept. Agr. Leaflet 160, 8 pp.
____ and KNIGHT, W. E. 1962. CRIMSON CLOVER. In Hughes, H. D., Heath, M. E., and Metcalfe, D. S., Forages - The Science of Grassland Agriculture, ed. 2., pp. 180 - 186. The lowa State College Press, Ames.
JOHNSON, W. C., and NETTLES, W. C.
1953. POLLINATION OF CRIMSON CLOVER: 1952 DEMONSTRATION RESULTS. S.C. Ext. Serv., Misc. Publ. (Unnumbered), 6 pp.KILLINGER, G. B. and HAYNIE, J. D.
1952. HONEYBEES AND OTHER FACTORS IN FLORIDAÕS LEGUME PROGRAM. Fla. Agr. Expt. Sta. Bul. 497, 14 pp.KNIGHT, W. E.
1969. INHERITANCE OF AN APETALOUS, MALE-STERILE CHARACTER IN CRIMSON CLOVER. Crop Sci. 9: 94.____ and GREEN, H. B. 1957. BEES NEEDED FOR POLLINATION OF CRIMSON CLOVER. Miss. Farm Res. 20: 7.
LOVELL, J. H.
1926. HONEY PLANTS OF NORTH AMERICA 408 pp. A. I. Root Co., Medina, Ohio.PEDERSEN, M. W., JONES, L. G., and ROGERS, T. H.
1961. PRODUCING SEEDS OF THE LEGUMES. U.S. Dept. Agr. Yearbook 1961: 171-181.PIETERS, A. J., and HOLLOWELL, E. A.
1937. CLOVER IMPROVEMENT. U.S. Dept. Agr. Yearbook 1937: 1190-1214.UNITED STATES DEPARTMENT OF AGRICULTURE.
1967. GROWING CRIMSON CLOVER. U.S. Dept. Agr. Leaflet 482, 8 pp.WEAVER, N., and FORD, R. N.
1953. POLLINATION OF CRIMSON CLOVER BY HONEYBEES Tex. Agr. Expt. Sta. Prog. Rpt. 1557, 4 pp.
