TREFOIL
Lotus spp., family LeguminosaeThree species of birdsfoot trefoil are of agronomic importance in the United States. They are broadleaf trefoil (L. corniculatus L.), narrowleaf trefoil (L. tenuis Waldst. & Kit. ex Willd.), and big trefoil (L. uligznosus Schk.) (Seaney and Henson 1970). Some experts disagree in the classification of the various species and cultivars of the genus Lotus (Gist 1960, Howell 1948, Levy 1918, MacDonald 1944, McKee and Schoth 1941, Seaney and Henson 1970, Wheeler and Hill 1957*).
In the United States, birdsfoot trefoil is grown for hay and permanent pasture, primarily in the New England States and western Oregon, and to a limited extent in several other Central and Northern States. Practically all big trefoil seed is produced in Oregon. According to Seaney and Henson (1970), over 2 million acres of trefoil were grown in 1967, and potentially the crop can produce 600 to 1,000 pounds seed per acre.
Plant:
Trefoil is a perennial plant that has an extensive root system with a strong taproot. It is therefore more drought-resistant than many other legumes. If conditions are unfavorable, the plant may grow only a few inches tall, but if favorable it may produce 100 or more stems and reach a height of 3 feet. It is the only legume with five leaflets, which consist of a terminal and two opposite lateral ones at the apex and two opposite leaflets at the base of the leaf petiole (fig. 186) (Hughes 1951).
The plant shape varies greatly between cultivars (Peterson et al. 1953). Some plants tend to grow upright (hay types), and some tend to be low or prostrate growing (pasture types).
Ten or more seed are produced in a cylindrical pod an inch or more long. Several seed pods are attached to the stem at a single point, and toward maturity they spread apart on a lateral plane giving the appearance of a bird's foot. The pods dehisce or pop open on maturity and the seeds are scattered. A nondehiscent type of plant would greatly increase the volume of seed harvested.
[gfx] FIGURE 186. - Broadleaf birdsfoot trefoil showing flowers, pods, and leaves.
Inflorescence:
Trefoil flowers are borne in an umber or cluster at the end of a short flowering stem, somewhat like sweet peas. Big trefoil usually has 8 to 12 flowers in a cluster or umber, and it has vigorous underground stems or spreading rhizomes. Broadleaf and narrowleaf trefoils have only five (rarely six to seven) flowers in the umber, and they do not have spreading rhizomes. The flowers of narrowleaf trefoil are smaller than those of broadleaf. They are bright yellow to orange, about one-half inch broad, and shaped much like the garden pea but much smaller. Knuth (1908*, pp. 300- 304) stated that the nectar is secreted in the usual place, at the base of the staminal column, and is sought after by numerous insects. He stated that the 10 anthers dehisce before the flower opens, then they shrivel. Then five of the filaments become club shaped and elongate to form a pistonlike action that pushes the dehisced pollen forward into the keel tip.
When the insect exerts pressure on the petals, the thickened filaments push a quantity of pollen out the keel opening. As the pressure increases, the stigma also protrudes and becomes exposed so that either self- or cross-pollination may take place. The former, however, is largely ineffective. When the pressure is removed, the parts return to their original position. The pollen is extruded in a ribbonlike somewhat pasty mass, and when contact is made it adheres to the underside of the bee. As further pressure causes the stigma to emerge, it also contacts the same area of the body of the insect, which may be coated with pollen obtained from other blossoms, and cross-pollination can result (Watson 1963). Release of pollen may result from as many as 10 bee visits. Flowers not visited by bees remain open 8 to 10 days, but visitation by bees (and probably fertilization of the stigma) reduce this period to less than 4 days.
Trefoil is highly attractive to bees for its nectar and pollen. When foraging on trefoil is extensive, colonies frequently build up rapidly and then swarm (Anonymous 1959).
Vansell46 reported that honey bees were extremely active on trefoil blossoms, collecting both nectar and pollen, although "little nectar could be seen in the 2 large pit-like nectaries." He noted six bees per square yard mainly collecting trefoil pollen. Pellett (1944) considered broadleaf birdsfoot trefoil in Iowa more attractive to bees than sweetclover. Trefoil produces a superb honey, although on a national scale the amount produced annually is not great.
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46 VANSELL, G. H. [BIRDSFOOT TREFOIL.] U. S. Dep. Agr., Pacific States Bee Culture Field Lab., Davis, Calif. First Quart. Rpt., p. 8. 1952.Pollination Requirements:
The rather thorough study of the pollination of the trefoils by numerous workers (Bader and Anderson 1962, MacDonald 1944, Miller and Amos 1965, Miri and Bubar 1966, Morse47 1958, Silow 1931) leaves little doubt that these plants require insect pollination for commercial production of seed. The flower is so constructed that pollen is released before the flower opens (Seaney and Henson 1970), and self-pollination appears feasible. MacDonald (1944) showed that single plants of L. corniculatus enclosed with "sterile" bees produced 100-percent fertilized florets, which proved that the plant was self-fertile. However, plants from which bees were excluded produced no fertilized ovules, which proved that the florets were incapable of fertilizing themselves without the aid of an outside agency. Other workers concluded that trefoils are only partially self-fertile. In any event, they are not self- fertilizing. MacDonald (1944) also showed that about twice as many flowers were fertilized with pollen from other plants of the same species as with pollen of the same plant. Even if individual trefoil plants are self- fertile, they benefit from cross-pollination between plants within the species.
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47 MORSE, R. A. THE POLLINATION OF BIRDSFOOT TREFOIL. 119 pp. 1955. [Unpublished diss. submitted to Cornell Univ., partial fulfillment for Ph.D. degree, Cornell Univ., New York.]Pollinators:
Bees are the only insects that pollinate the trefoils to an appreciable degree (Bader and Anderson 1962, MacDonald 1944, Morse48, Peterson et al. 1953, Vansell49 ). Honey bees and bumble bees account for the big majority of the bee visitors, and of these the honey bee is predominant (Morse 50 ). Although Bohart (1960*) recorded higher populations of wild bees than honey bees on plots of trefoil in Utah, Bader and Anderson (1962) concluded that pollen-collecting honey bees were better pollinators of L. corniculatus than were nectar collectors in that the former set 7.00 seeds per pod, whereas the latter set only 4.92 per pod. (A pod can have 10 or more seeds.) Miller and Amos (1965) concluded that about two-thirds of all trefoil flowers set as many seeds from one honey bee visit as if five or six visits had been permitted. Morse (1958)51 stated that slightly less than one honey bee per square yard of flowering trefoil was a sufficient pollinator population in New York. Vansell52 observed six bees per square yard in California, but the significance of this bee population in terms of seed production is unknown.
Miller (1969) noted that clones differ in cross-compatibility to the extent that some crosses set very few seeds. If this condition exists under field conditions, and it could quite logically do so, such a cross- visit would require an additional bee visit from a more acceptable clone if seed is to be set. To that extent, heavy visitation might be desirable.
Because of the tendency of the seeds to set over a period of several weeks and to shatter when they become ripe, the harvesting of large crops of seed is difficult. McKee and Schoth (1941) stated that 100 pounds of clean seed per acre was usual. MacDonald (1944) reported the production of 22 growers averaged only 46 pounds. Howell (1948) reported an average of 127 lb/acre in Oregon. Tremblay (1962) reported 99 and 139 lb/acre in Vermont for 1958 and 1959. (Incidentally, he reported that the cost of bees for trefoil pollination ranged from $0.04 to $3.56 (average, $1.16) per acre.) Anderson (1956) found that least shattering and maximum seed was obtained if harvest occurred when the maximum number of pods were light green to light brown. Peacock and Wilsie (1957) showed that shattering was reduced by 17 percent in one cycle of plant selection, and they believed that nonshattering plants might be developed.
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48 See footnote 47.
49 See footnote 46.
50 See footnote 47.
51 See footnote 47, p. 362.
52 See footnote 46, p. 362.Pollination Recommendations and Practices:
Morse (1958) was of the opinion that in central New York - where apiaries of 25 to 50 colonies were about 2 miles apart (one colony per 50 to 100 acres) - sufficient bees were in the area and moving colonies into the area for pollination of trefoil would be of little or no value. He was probably giving more consideration to honey production than pollination of trefoil, or he gave considerable credit to local wild bees. Wheeler and Hill (1957*) stated that insect pollination appeared to be essential for seed production of big trefoil, but if the supply of local bees was not adequate additional honey bees should be added. Eckert (1959*) recommended one strong colony per acre of trefoil. He stated that colonies of bees interchanged between trefoil and alfalfa reportedly gave excellent service. Smith (1960) recommended two to three colonies of honey bees per acre of trefoil, the colonies placed in or close to the field.
The number of bee visitors per unit area of the crop should be considered when determining the adequacy of the population. Morse 53 considered one bee per square yard adequate, although Vansell54 observed as many as six bees per square yard. The grower wants to set the maximum seed crop in as short a period as possible. It would appear then that he should strive for the bee population that would accomplish this. If that population is not present, additional colonies should be brought in until it is reached. This may require more than the one colony indicated by Morse or the two to three colonies recommended by Smith (1960).
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53 See footnote 47, p. 362.
54 See footnote 46, p. 362.LITERATURE CITED:
ANONYMOUS.
1959. POLLINATION OF BIRD'S FOOT TREFOIL. Amer. Bee Jour. 99: 90-91.ANDERSON, S. R.
1955. DEVELOPMENT OF PODS AND SEEDS OF BIRDSFOOT TREFOIL, LOTUS CORNICULATUS L., AS RELATED TO MATURITY AND TO SEED YIELDS. Agron. Jour. 47: 483.BADER K. L., and ANDERSON, S. R.
1962. EFFECT OF POLLEN AND NECTAR COLLECTING HONEYBEES ON THE SEED YIELD OF BIRDSFOOT TREFOIL, LOTUS CORNICULATUS L. Crop Sci. 2: 148-149.GIST, G. R.
1960. BIRDSFOOT TREFOIL. Ohio Agr. Ext. Serv. Bul. 401,16 PP.HOWELL, H. B.
1948. A LEGUME FOR ACID SOILS (LOTUS ULIGINOSUS (L. MAJOR). Oreg. Agr. Expt. Sta. Bul. 456, 25 PP.HUGHES. H. D.
1951. BIRDSFOOT TREFOIL MOVES WEST. Crops and Soils 4(3): 18-22.LEVY, E. B.
1918. THE BIRDSFOOT TREFOILS. New ZeaL Jour. Agr. 17: 347-351.MACDONALD, H. A.
1944. BIRDSFOOT TREFOIL (LOTUS CORNICULATUS L.) ITS CHARACTERISTICS AND POTENTIALITIES AS A FORAGE LEGUME. N.Y. (Cornell) Agr. Expt. Sta. Mem. 261,182 PP.MCKEE, R., and SCHOTH, H. A.
1941. BIRDSFOOT TREFOIL AND BIG TREFOIL. U.S. Dept. Agr. Cir. 625,13 PP.MILLER, J. D.
1969. CROSS-COMPATIBILITY OF BIRDSFOOT TREFOIL, LOTUS CORNICULATUS L. Crop Sci. 9: 552-555.______and AMOS, J. M.
1965. USE OF HONEY BEES TO POLLINATE TREFOIL IN THE GREENHOUSE. Amer. Bee Jour. 105: 50-51.
MIRI, R. K. and BUBAR, J. S.
1966. SELF-INCOMPATIBILITY OR AN OUTCROSSING MECHANISM IN BIRDSFOOT TREFOIL (LOTUS CORNICULATUS). Canad. Jour. Plant Sci. 46: 411-418.MORSE, R. A.
1958. THE POLLINATION OF BIRDSFOOT TREFOIL (LOTUS CORNICULATUS L.) IN NEW YORK STATE. In 10th Internatl. Cong. Ent. Proc. 4: 951-953, Montreal.PEACOCK, H. A., and WILSIE, C. P.
1957. SELECTION FOR RESISTANCE TO SEED POD SHATTERING IN BIRDSFOOT TREFOIL (LOTUS CORNICULATUS L.). Agron. Jour. 49: 429.PELLETT, F. C.
1944. BIRD'S-FOOT TREFOIL. Amer. Bee Jour. 84: 83-84.PETERSON, M. L., JONES, L. G., and OSTERLI, V. P.
1953. BIRDSFOOT TREFOIL IN CALIFORNIA. Calif. Agr. Expt. Sta. Cir. 421,15 PP.SEANEY, R. R., and HENSON, P. R.
1970. BIRDSFOOT TREFOIL. Adv. in Agron. 22: 119-157.SILOW, R. A.
1931. SELF-STERILITY OF LOTUS SPP. In Welsh Plant Breeding Sta., Aberystwyth, Self- and Cross- fertility and Flowering Habits of Certain Herbage Grasses and Legumes, Seasons 1921-1930, Bul. (Ser. H) 12: 234-240.SMITH, M. V.
1960. LEGUME POLLINATION IN ONTARIO. Ontario Dept. Agr. Pub. 139,7 PP.TREMBLAY, R. H.
1962. TREFOIL SEED PRODUCTION COSTS IN THE CHAMPLAIN VALLEY. Vt. Agr. Expt. Sta. Bul. 627,15 pp.WATSON, C.
1963. TREFOIL FOR THE FARMER. Amer. Bee Jour. 103: 219.
