Drs. Roger Morse and Nicholas Calderone recently updated the value of the pollination contribution made by managed honey bees in the U.S. They estimated the current value at $14.6 billion. The study was supported by the National Honey Board and was published in Bee Culture. The results of their study are also available on the Internet at: . This report is an invaluable resource for beekeepers who (1) contact legislators about beekeeping issues, (2) speak to school and civic groups, and (3) respond to media request for information. It includes images, tables and charts that can be used to support presentations on the value of honey bee pollination.

Studies like the Cornell pollination study are critical to maintaining a positive environment for beekeeping. All beekeepers should carefully read the report and make a list of useful facts to incorporate into their discussions about honey bees. Many beekeepers stress the value of honey bee pollination in interviews and presentations but provide little research-based data. By supporting statements about the importance of honey bee pollination with data from the Cornell study, beekeepers can do a much more effective job of communicating the importance of honey bee pollination. All beekeepers should thank the researchers, the National Honey Board, and the A.I. Root Company for providing this outstanding resource.

Beekeeping is taught as a 2-credit hour class each spring semester at the University of Nebraska, and students are required to write a term paper. This year Bill McCormick wrote an excellent paper on clover biology. With his permission, I am reproducing a portion of his paper for Bee Tidings subscribers. Successful beekeeping requires a knowledge of both bee and plant biology. Many beekeepers know a great deal about bees but little about the plants they depend on. I hope you enjoy Bill's paper.

True clovers belong to the genus Trifolium, which includes a total of about 250 diverse species. The Dutch word for clubs is "klafer", which the three leaflets of clover plants resemble, may be the origin of the word "clover" (Evans, 1957). The term "clover" is also used as the common name of a few legumes with clover-like leaves, e.g. white sweet clover, Melilotus alba Desr., which is not a true clover.

In general, clovers inhabit temperate regions of the world. Cool moist climate is required, or growth is confined to the season of the year when cool climatic conditions prevail. Clovers will grow on many different soils if climatic conditions are favorable.

Although some species are native to North America, most clovers of agricultural interest were introduced from Europe. About 15 species of true clovers and four species of sweet clovers are used in American agriculture to an important extent, and of these, only two species of sweet clover and four or five true clover species occupy significant area (Hermann, 1953; Hollowell, 1960).

The beneficial effects of clovers have not always been known or appreciated by farmers. Bare fallow was a common practice (particularly among British farmers), and its replacement with clover met with some resistance. However, Piper (1924) stated that red clover has had a greater influence on civilization than the potato and much greater than any other forage plant. The underlying reason for the importance of clover (and other legumes) is their potential for fixing atmospheric nitrogen.

The clovers are among the most important honey plants for the quantity and quality of honey produced. In this paper three types of clovers are discussed that are of interest to beekeepers, white Dutch clover, red clover, and the sweetclovers. However, many other clovers not included in this review are important to bees.

White clover is scattered throughout the United States. Plants may be found wherever there is sufficient moisture to enable them to survive. Early European settlers brought white clover, Trifolium repens L., to America (Carrier and Bort, 1916). In the U.S. and Canada the spread of this clover was rapid. The American Indian's word for white clover means "white man's foot" and is probably a reference to the survival and flourishing of the small white clover under the impact of treading along rural paths.

White clover is widely distributed in the world, from the Arctic Circle to cool, temperate sites on tropical mountains. It grows best in humid sections of the temperate zones during cool, moist seasons. It grows in parks, in pastures, along roads, and in other locations where the soil is fertile, moisture is provided, and tall plants are controlled by grazing or clipping. It is not tolerant of drought, excess water, or soils that are saline, highly alkaline, or acid (Cope and Gibson, 1985).

White clover volunteers in pastures when conditions are favorable. The presence of the clover may barely be noticed and its contribution may be attributed to another forage. A much greater contribution from clover can be obtained by planting improved cultivars and by using good management practices. A cardinal requirement of successful management is controlling the height and density of associated plants to expose the clover to light. Violation of this requirement is a common mistake in the management of clover-grass pastures (Cope and Gibson, 1985).

White clover can continue growing in an area for a period of years either 1) as a reseeding annual (i.e., annually producing seed that, in turn, produce volunteer plants), or 2) as a perennial that propagates itself asexually (i.e., after death of the primary axis, rooted stolons form new growth centers that function similarly to seedlings). Apparently in many pastures white clover is a mixture of plants arising from the two systems (Hollowell, 1966).

Grazing or mowing the pasture to control competition from the associated grass and weeds is important to clover longevity. Reduced competition helps in the establishment of volunteer seedlings and in the formation of new growth centers by rooted stolons.

White clover-grass pastures should be established and managed to maximize the benefits derived from the nitrogen-fixing ability of the clover. The benefits are improved forage quality and high forage production without nitrogen fertilizer. The mixture will produce nearly as much forage as a pure stand of grass with optimum nitrogen fertilization and will provide a longer grazing season (Cope and Gibson, 1985).

In the first year after a pasture has been seeded with a white clover-grass mixture, the clover may produce more than 50% of the total forage. The forage is of high quality for either beef or dairy animals. In the following years the percentage of clover in the mixture tends to decline. When clover represents less than 20% of the total forage, clover should be reseeded into the sod (Cope and Gibson, 1985).

White clover is an important honey plant. White clover honey is considered the best quality honey. It is the standard to which other honeys are compared. In many areas it is the principle source of nectar for the production of surplus honey. The best yields come in seasons following a year of excessive rainfall. In wet years the conditions favor the rooting of thousands of new plants, which are ready to produce a crop of nectar the following summer (Pellet, 1976).

Honey bees are also used for pollinating white clover grown for seed. Tests indicate that from 2.5 to 4 strong colonies per hectare are sufficient for pollination of ladino clover in California (Marble et al., 1970). Bumblebees and other wild bees also pollinate white clover, but their numbers are usually inadequate to obtain effective pollination.

There are probably twenty species of melilotus native to the temperate regions of Europe and western Asia. Only biennial white, Melilotus alba, and biennial yellow, Melilotus officinalis, are grown extensively in the central and northern regions of the United States. Sweet clover thrives under conditions of drought where other clovers fail. Wild sweet clover is usually found along roadsides, in fencerows and in wasteland.

Sweet clover is grown primarily for pasture and soil improvement. It is commonly preferred to alfalfa for use is short rotations and for pasturing certain kinds of livestock, green manuring, and for growing on the less favorable soil types. Increased yields of other crops generally follow its use in the cropping system. Under conditions of abundant moisture, sweet clover is most effective for soil improvement when plowed under in the spring of the second year after 10 to 12 inches of plant growth has been made. Volunteer growth is not a problem when the crop is handled in this manner (Garver et al. 1943).

In its first year the growth of biennial sweet clover is leafy and much like alfalfa in quality. Second year growth arises from crown buds formed underground in the preceding fall. Its growth is rapid through April and May of the second year, (white sweet clover may reach a height of seven feet), its stems becoming comparatively coarse with the approach of maturity. For the production of good quality hay, second year growth requires early harvest and favorable curing conditions. To insure continuous pasture and hay through a period of successive years, it is necessary that new seedlings be established each year (Garver et al. 1943).

Sweet clover was not always a desired plant. Before about 1900 many people considered it a weed. It was a popular thing for the beekeepers to buy sweet clover seed and stealthily sow it along the roadsides. Whenever the plant showed up in a new area the nearby beekeepers were blamed. This created ill feelings in some areas. In some states it was placed on the list of noxious weeds and its eradication required by law (Pellet, 1976). Following World War I the status of sweet clover changed rapidly from a weed to an excellent plant for green manuring and temporary pasture in the Corn Belt States.

Sweet clover is an excellent source of high quality honey. Sweet clover reaches the highest development in nectar secretion in the hot, dry summer climate of the plains region between the Mississippi River and the Rocky Mountains. The yellow variety blooms about two weeks earlier than the white and where both are present a long honey flow may be expected (Pellet, 1976). In Nebraska, if both varieties are planted the honey flow season extends from the beginning of June to the end of July or longer if moisture conditions are suitable (Garver et al. 1943). Where it is grown widely as a farm crop, an average of 200 pounds surplus per colony is not uncommon (Pellet, 1976). The quality of the honey is excellent. It is light in color and mild in flavor. It granulates more readily than white Dutch clover, but is regarded as the highest quality honey in the market (Pellet, 1976).

Red clover, Trifolium pratense L., is recognized as one of the most important legumes in the world. It originated in Europe and Asia and was introduced to the United States by European colonists. Grown alone or with grasses, red clover is adapted to a wide range of soil types, pH levels, and environmental conditions. Red clover is grown for hay, silage, pasture, and soil improvement in much of the temperate regions of the world (Bowley et al. 1985).

Two main types of red clover are grown in North America: medium or double-cut, and mammoth or single-cut. Where adapted, the mammoth type matures later, is taller, and yields more than the medium type in the first growth. The medium type, most prominent in North America, may produce several growths a year depending upon the length of growing season (Bowley et al. 1985).

Red clover is currently used extensively in pasture renovations. Extremely high seedling vigor and tolerance of shading make it one of the easiest legumes to establish in mature grass sods (Bowley et al. 1985).

Red clover is a short-lived perennial that is productive for about three seasons. A volunteer crop of clover seedlings may be obtained by allowing seed to mature and fall to the soil. Renovation, rather than natural reseeding, is the recommended practice to ensure a uniform, productive stand of red clover. Pastures will usually require renovation every 3rd to 4th year (Bowley et al. 1985).

Red clover is considered a very important honey plant in some areas. Red clover produces good quantities of nectar but because of the long length of the corolla tube, honeybees are not always able to take full advantage of it. Some breeders have tried to develop varieties with shorter corolla tubes to increase the usefulness as a honey plant and to improve the pollination effectiveness of the visiting bees, thereby increasing seed yield. Zofka and Kellner are two varieties that have shorter corolla tubes, but they do not yield well or have the other desirable characteristics of the common varieties.

Bumblebees are especially effective pollinators of red clover grown for seed production, but they often are inadequate in numbers to insure a good seed crop. Therefore it is usually necessary to provide honey bees to obtain adequate red clover pollination. However, the presence of more attractive nectar-producing plants in the vicinity or locating colonies too far from the crop can result in inadequate pollination (Peterson et al. 1960; Justin et al. 1967). If more attractive plants are not nearby, five colonies of honey bees per hectare are usually recommended. The colonies should be placed in or adjacent to red clover seed fields when the plants begin to bloom.

Clovers are the most important honey plant in North America, but their contribution to honey production has decreased over the last fifty years. In the first half of the twentieth century clovers were grown extensively in agricultural cropping and pasture systems because of the clover's ability to fix free nitrogen. With the increase in the use of nitrogen fertilizers, farmers have relied less on clovers to fix nitrogen. In addition, some farmers have switched to soybeans in their crop rotations instead of using clovers. Forage crop plantings of clovers are also greatly reduced. Alfalfa has become the preferred forage crop and is generally harvested before the blooms are of much value to the bees. Today there are relatively few areas where there are large amounts of clovers grown in agricultural crop rotations.

If the benefits of organic farming are promoted, there could be an increase again in the use of clovers in crop rotation systems. Clovers are an excellent source of "natural" nitrogen for the organic crop producer. The clovers will continue to be an important honey plant in the North America. Because of their importance to the beekeeper, students of beekeeping should become familiar with the different types of clovers that benefit the honey bee.

Bowley, S. R., R. R. Smith, and N. L. Taylor. 1985. Red clover. p. 457-470. In Clover science and technology. N.L. Taylor (ed.). American Society of Agronomy, Inc., Madison, Wisconsin.

Carrier, L., and K. S. Bort. 1916. The history of Kentucky bluegrass and white clover in the United States. J. Am. Soc. Agron. 8:256-266.

Cope, W. A., and P. B. Gibson. 1985. White clover. p. 471-490. In Clover Science and Technology. N.L. Taylor (ed.). American Society of Agronomy, Inc., Madison, Wisconsin.

Evans, G. 1957. The clover tradition in Wales. J. Agric. Soc. Coll. Wales 38:30-35.

Garver, S., J. M. Slatensek, and T. A. Kiesselbach. 1943. Sweetclover in Nebraska. The Experiment Station. University of Nebraska, College of Agriculture, Lincoln, Nebraska. December, 1943, Bull. 352, p.1-8.