ALSIKE CLOVER11
Trifolium hybridum L., family LeguminosaeAlsike clover has been an important summer legume in north central and Northeastern United States; however, it is being replaced by alfalfa. A small amount of seed is produced in the Pacific Northwest. Most of the seed that we use comes from Canada. In 1969, we imported 3,715,000 pounds, most of which was probably used in mixed pasture planting.
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11 See "Clovers General, " p. 158.Plant:
Alsike clover is a perennial but usually grows as a biennial, and in some situations it behaves as an annual. It is intermediate in size between white and red clover. Many smooth stems, bearing smooth trifoliate leaves, arise from its crown. The noncreeping stems may grow to a height of 5 feet but usually reach about 2 feet. They bear flower heads along their entire length, the youngest always toward the top. It is a good hay, pasture, and green manure crop, and like other legumes, it improves the soil and contributes to reduced soil erosion.
Inflorescence:
The flower head of alsike clover is made up of many florets and is similar to the more common white clover, although there may be four times as many heads per square yard as are normally found on white clover. The florets on some heads are pink, on others they are white, and on some they are both pink and white. This variation in flower color led to an earlier belief that alsike was a cross between red and white clover, hence the scientific name hybridum.
A floret will produce two to three seeds. Flower heads with 100 seeds indicate a good seed crop. The flowers are quite attractive to bees, especially honey bees, for the nectar and pollen. Pellett (1923) stated that some beekeepers estimated that alsike clover might produce 500 pounds of honey per acre in good seasons. This seems abnormally high but indicates the importance beekeepers attach to this crop as a source of honey. Holmes (1960) noted that boron favorably influenced nectar secretion in alsike clover, but apparently this information has not been used to increase seed production.
Pollination Requirements:
The florets are largely self-incompatible so they must receive pollen from another plant to produce seed (Pieters and Hollowell 1937). In Ohio, Dunham (1939) showed that three cultivars set only 0.4 to 5.5 seeds per head when selfed, 3.4 seeds per head when wind pollinated, and 120 to 125 seeds per head in a cage with bees. Open plots had 2.6 to 90.4 seeds per head. He calculated that the seed yielding capacity of a field with 1,000 heads per square yard, averaging 50 seeds per head, would be 350 pounds per acre, 90 seeds per head would produce 625 lb/acre and with 120 seeds per head the yield would be 825 lb/acre.
In Oregon, Scullen (1956*) reported 5.1 seeds per head where bees were excluded but 69.2 seeds per head where bees had access to them. (About 500 lb/acre, according to Dunham's (1939) method of calculation.) Oregon averages 300 to 415 lb/acre, but occasional phenomenal yields of 1,000 lb/acre are obtained. The overall United States average is about 140 lb/acre (Wheeler and Hill 1957*). Evidently, seed production in most areas could be significantly increased with adequate pollination.
Pollinators:
Few detailed studies have been made on the insect pollinators of alsike clover. Megee and Kelty (1932) concluded that the honey bee was an effective pollinator on alsike clover in Michigan. Dunham (1957) studied alsike clover seed setting for a number of years in an area of Ohio where intensive farming was practiced. He found that native bees set only 1.5 to 3 percent of the seeds. Valle (1960) reported that in Finland the honey bee was a much more important pollinator of alsike clover than bumble bees. According to Pankiw and Elliott (1959), the honey bee is the primary pollinator of alsike clover in western Canada. They found that fields with higher populations of pollinators matured earlier as well as produced more seed. Harrison et al. (1945) concluded that honey bees were essential to alsike clover in Michigan. Tucker et al. (1958) reported that honey bees comprised 93 to 99 percent of the pollinating insects on alsike clover in Minnesota. Smith (1960) stated that honey bees represent 83 percent of the total pollinator population on alsike fields in southern Ontario.
Pankiw and Elliott (1959) stated that honey bees are excellent pollinators of alsike clover and that they visited the florets at the rate of 18.7 per minute, as compared to 20.0 per minute for leafcutter bees, and 28.6 per minute for bumble bees. Fischer (1954) reported that honey bees will leave alsike for sweetclover. Wahlin (1962) observed that when widespread cultivation of oil plants occurred in the red and alsike clover seed growing area of Sweden, the bees visited these crops, which resulted in a reduced clover seed harvest.
Holdawav et al. (1957) in three observations over 2 years obtained yields of 15, 20, and 20 pounds of seed per acre without insect pollination; 102, 207, and 368 lb/acre with insect pollination, no harmful insect control and no fertilizer added; and 685, 691, and 808 pounds of seed per acre with pollination, harmful insect control, and the addition of phosphorus and potash fertilizers. They recommended at least two colonies per acre, the colonies placed at the edge of the field.
Studies have established that the honey bee is the primary insect pollinator of alsike clover and its activity accounts for the bulk of the seed produced. Evidently, seed production of this crop can be significantly increased over current commercial averages if honey bees are present in adequate numbers.
Pollination Recommendations and Practices:
Pankiw and Elliott (1959) recommended one colony of honey bees per acre of alsike clover for fields of 50 acres or more but up to three colonies per acre for smaller fields. They obtained about 375 pounds of seed per acre with a bee population of about three-quarters of a bee per square yard. Smith (1960) recommended two to three colonies per acre with the colonies placed in or close to the field. Holdaway et al. (1957) recommended at least two colonies per acre. Tucker et al. (1958) concluded that seed yields were increased about 260 lb/acre for each colony per acre. They calculated that one bee per 3 yd2 set 175 pounds of seed per acre, but one bee per square yard set 800 pounds of seed per acre. The number of colonies per acre necessary to provide the one bee per square yard was not indicated.
Dunham (1938) thought that the number of colonies necessary to provide maximum pollination of alsike might be so great it would make the renting of bees prohibitive. No study has been made to determine this factor. The data indicate, however, that the alsike seed grower can afford to and should obtain several colonies per acre at current colony rental prices (see "Pollination Agreements and Services").
LITERATURE CITED:
DUNHAM, W. E.
1938. INSECT P0LLINATION OF ALSIKE CL0VER. Gleanings Bee Cult. 66: 425.______ 1939. THE IMPORTANCE OF HONEYBEES IN ALSIKE SEED PRODUCTION. Gleanings Bee Cult. 67: 356-358, 394.
DUNHAM, W. E.
1957. GREATER BEE CONCENTRATION IS NEEDED FOR ADEQUATE POLLINATION OF CLOVER FIELDS. Gleanings Bee Cult. 85: 218-219.FISCHER, R. L.
1954. HONEYBEES AID PRODUCTION OF ALSIKE CLOVER SEED. Minn. Farm and Home Sci. 11(3): 7-9.HARRISON, C. M., KELTY, R. H., and BLUMER, C.
1945. HONEYBEES AND LEGUME SEED PRODUCTION. Mich. Agr. Expt. Sta. Quart. Bul. 28(2): 1 - 5.HOLDAWAY, F. G., BURSON, P. M., PETERSON, A. G., and others.
1957. BETTER LEGUME SEED PRODUCTION. Minn. Farm and Home Sci. 14(3): 11-13.HOLMES, F. O.
1960. BORON DEFICIENCY AS A PROBABLE CAUSE OF THE FAILURE OF BEES TO VISIT CERTAIN FLOWERS. Amer. Bee Jour. IOO: 102 - 103.MEGEE, C. R., and KELTY R. H.
1932. THE INFLUENCE OF BEES UPON CL0VER AND ALFALFA SEED PRODUCTION. Mich. Agr. Expt. Sta. Quart. Bul. 14(4): 271-277.PANKIW, P., and ELLI0TT, C. R.
1959. ALSIKE CL0VER P0LLINATION BY HONEY BEES IN THE PEACE RIVER REGION. Canad. Jour. Plant Sci. 39(4): 505-511.PELLETT F. C.
1923. AMERICAN HONEY PLANTS. 392 pp. American Bee Journal, Hamilton, III.PIETERS, A. J., and HOLLOWELL, E. A.
1937. CL0VER IMPROVEMENT. U.S. Dept. Agr. Yearbook 1937: 1190-1214.SMITH M. V.
1960. LEGUME P0LLINATION IN ONTARI0. Ontario Dept. Agr. Pub. 139, 7 pp., Toronto.TUCKER, K. W., FURGALA, B., and KIECKHEFER, R. W.
1958. HONEY BEES INCREASE ALSIKE CL0VER SEED YIELDS. Minn. Farm and Home Sci. 15(2): 3.VALLE, O.
1960. [POSSIBILITIES OF ALSIKE CLOVER SEED PRODUCTION IN FINLAND. Maatalous ja Koetoim. 14: 118-127. [In Finnish, English summary.] AA-395/62.WAHLIN, B.
1962. THE UTILIZATION OF HONEY BEES IN SEED PRODUCTION. In 1st Internatl. Symposium on Pollination Proc., Copenhagen, Aug. 1960, Commun. 7, Swedish Seed Growers' Assoc., pp.95-97.