ISSUED: 3-84
Timothy H. Taylor

Department of Agronomy
Bird's-foot trefoil (Lotus corniculatus L.) is a perennial forage legume used for pasture, hay and silage in many regions of the world. In the United States and Canada, two distinct plant types are grown: the New York or 'Empire' type, and the European type. Empire is a low growing variety used primarily for pasture while the European type is taller growing and may be used for pasture or hay. Most of the named varieties in the U.S. were developed from the tall growing forms.

Origin and Development of Bird's-foot Trefoil
A mixture of equal parts of certified Empire and imported French bird's-foot trefoil seed was sown in April 1954 as one of the treatments in a grazing experiment on the experimental farm in Woodford County, Kentucky. The following September, Kentucky bluegrass was sown into the trefoil stand. Four experimental bluegrass-trefoil pastures and a reserve area were grazed from 1955 through 1958. The reserve pasture was grazed from 1959 through 1969. During 1969, sufficient seed was harvested from 15-year-old stands for experimental testing and to make a seed increase planting. Two acres were sown with Kentucky bluegrass as a seed-increase field in September 1969 with first generation seed harvested in 1970. From 1970 through 1976, Kentucky Ecotype, the designated name for testing, was advanced four generations. The fourth generation seed has been designated as breeders' seed.
Kentucky Ecotype trefoil was released by the University of Kentucky Agricultural Experiment Station in 1980 after testing over a 15-state area from Alabama to Minnesota and from the east coast to Kansas. This variety was named Fergus to honor Dr. E.N. Fergus for his outstanding contributions in forage crops over a fifty-year period at the University of Kentucky.

Plant Type and Adaptation of Bird's-foot Trefoil
Fergus bird's-foot trefoil is medium in growth habit--taller than 'Dawn' from Missouri, shorter than 'Viking' from New York, and near the same height as 'Carroll' from Iowa. Fergus contains a wide range of plant types. In Kentucky, it flowers 3 to 5 days earlier and blooms longer than Carroll. It is a high seed-producing variety in Kentucky and in other places in the U.S.
Fergus trefoil is adapted to Kentucky's climate as well as throughout much of the humid transition zone of the eastern U.S. It is well adapted to the northern tier of states from Pennsylvania to Iowa and has been equal or superior to other named varieties in Mississippi, Alabama, Georgia and Tennessee. In Kentucky, the forage yield and persistence of Fergus has been superior to Dawn, Carroll and Viking. In strip-mine spoil reclamation studies in Kentucky, Fergus has done well compared with other trefoil varieties and other forage legumes.

Characteristics of Bird's-foot Trefoil As a Pasture and Hay Plant

Favorable characteristics of bird's-foot trefoil are that it:
1)is a perennial that will naturally reseed if permitted to set seed,
2)causes no bloat in cattle or sheep,
3)is a high quality forage--acceptable even after seed sets,
4)is more drought, heat and cold tolerant than white or red clover,
5)will grow on less fertile, more acid soils than alfalfa but still responds to high fertility,
6)grows well with most cool-season grasses,
7)is high in protein, especially in its immature stage, and
8)fixes nitrogen for associated grass.

Unfavorable characteristics are that bird's-foot trefoil:
1)is slow to establish and sensitive to weed and crop competition, and
2)is susceptible to the fungus disease Rhizoctonia solani that may kill or thin stands in warm, humid conditions.

This fungus disease may be quite troublesome during summer months in Kentucky and throughout the humid transition zone of the eastern U.S. However, both of these above unfavorable characteristics may be greatly reduced or eliminated by careful management during and after establishment.

Comparisons With Other Legumes in Renovation Study
Alfalfa, red clover, white clover and trefoil were sod-seeded in the spring into Kentucky bluegrass and tall rescue sod land at Lexington. An unseeded check plot was provided to compare production with the seeded plots (Table 1). These data show red clover, alfalfa and white clover are more productive in the establishment year than trefoil. Legume establishment rates as determined by relative yields were: check-no legume seed 100, trefoil 132, white clover 180, alfalfa 206, and red clover 280. However, trefoil improved yield and legume content over the check. Trefoil is slower in establishing than the other legumes primarily because of slow seedling growth and the perennial characteristic of the species. Note also that alfalfa is slower in establishment than red clover.

Table 1. Comparison of Fergus trefoil with other legumes in a spring-sown
renovation study during the establishment year, 1976.
Relative Rate
of Establishment, 
and grasses
lb. seed/A
Ky Bluegrass
'Ky 31'
Tall Fescue
Yield2, lb/A Legume, % Yield, lb/A Legume, %
Trefoil, 6 2,900 52 3,600 46 132
White Clover, 2 3,700 31 5,300 27 180
Red Clover, 8 6,100 66 7,900 61 280
Alfalfa, 15 4,400 45 5,900 32 206
Check - No legume 2,200 trace 2,800 trace 100
1Varieties sown were: 'Fergus' trefoil, 'Tillman' white clover, 'Kenstar' red clover, and 'Vernal' alfalfa.
2 Grass was cut above legume seedlings two times. Grass-legume vegetation was harvested in early July, late August and early November.

Table 2. Comparison of the productivity of Fergus trefoil with other legumes and grasses receiving different rates of nitrogen fertilizer in a spring renovation study after the establishment year, 1977, 1981.
Species2 and
N, lb/A
5-Year Average After Establishment Year1
Kentucky Bluegrass
Tall Fescue
Yield, lb/A Legume, % Protein, lb/A Yield, lb/A Legume, % Protein, lb/A
Trefoil 6,800 55 1,330 7,500 51 1,370
White Clover 4,800 32 820 5,200 26 860
Red Clover 6,300 62 1,140 6,700 51 1,220
Alfalfa 9,600 79 2,050 9,100 69 1,800
N on Grass Sod3  
None 2,700 15 430 2,900 trace 390
89 4,000 trace 560 5,500 0 680
178 5,900 0 990 7,500 0 1,200
268 7,100 0 1,320 9,300 0 1,570
1All treatments were harvested 5 or 6 times each growing season to simulate pasture conditions: 5 harvests by Sept 10 - 20, final harvest after Nov 1.
2Fergus trefoil and Vernal alfalfa were sown in 1976 while Tillman white clover and Kenstar red clover were planted in 1976 and 1979.
3Each rate of nitrogen fertilizer was divided into three parts and each part applied at different times during the growing season

Table 2 shows the productivity of the same group of legumes over a five-year period after the establishment year. In this long-term experiment, unseeded grass sod plots were fertilized with different rates of nitrogen fertilizer. Red clover and white clover plots were seeded a second time after three growing seasons, while alfalfa and trefoil were seeded only one time. Harvesting management was the same on all treatments. Five or six cuttings each growing season were made to simulate pasture conditions.
Results show that alfalfa and trefoil are true perennials. Red clover and white clover were resown after three growing seasons to maintain acceptable production levels. At the end of the sixth growing season, good stands of alfalfa and trefoil remained while the clover stands were again extremely thin.
Of the legumes tested, alfalfa-grass mixtures were outstanding in yield, percent legume and crude protein production. Trefoil-grass mixtures were higher in dry matter yield than red clover-grass associations, while white clover was lower in productivity than the grass-red clover mixtures.
The grass-legume mixtures were generally higher yielding than the undisturbed grass sods receiving nitrogen fertilizer. However, very high rates of nitrogen applied on grass stands did increase dry matter production greater than that of trefoil-, red clover- and white clover-grass mixtures. Tall rescue was more productive than Kentucky bluegrass under all circumstances.

Establishing Stands
Sowing trefoil on a prepared seedbed or sod-seeding into a grass sod is somewhat different than planting red clover or alfalfa. Trefoil seedlings are small and slow growing, and the plants are sensitive to competition from other legumes, grasses, weeds and nurse crops.
Trefoil also is slow in establishing; one full year is required for a productive stand to develop. Because of the slow seedling growth, grass and weed competition must be controlled.

Prepared Seedbed Sowing in Spring.
For prepared seedbed spring sowings, you can apply the same herbicides that are normally used for establishing pure stands of alfalfa. In September of the same year, cool-season grasses may be drilled into the trefoil stand. Trefoil may be sown with a grass without the use of a herbicide in spring or late summer.

Sod Seeding in Spring or Late Summer.
When sod-seeding, plant into a nitrogen deficient grass sod that has been grazed or cut as short as possible. Continue to graze or clip closely for 6 to 8 weeks after seeding. The grass may be suppressed by a grass herbicide banded over the seeded row (see Extension publication AGR-26, "Renovating Grass Fields").
Spring seedings made without the use of herbicides may become weedy or grass dominant within 5 to 7 weeks after seeding. The weedy or grass vegetation may be clipped or grazed above the trefoil seedlings; after which, allow 5 to 6 weeks of growth before clipping or grazing again. The crop should be grazed or mowed by early to mid-September; allow it to grow until November after which it may be grazed. This growth period will assure high levels of root reserves for winter survival and the initiation of spring growth. Fall management is similar for alfalfa and trefoil.

Managing Established Stands of Bird's-foot Trefoil
Two management factors should be kept in mind for maintaining stands beyond the establishment year:
1) Keep the crop short during the summer months to prevent the buildup of diseases which thrive in the humid, hot conditions within the canopy of a tall, thick stand. Sun and wind near the ground surface will greatly retard disease damage.
2) Allow one crop to set seed and shatter to the ground once every two years. Seed production for natural regeneration of stands should begin after the crop is 2 or 3 years old (Table 3). The best period for seed production for stand regeneration appears to be from early August to mid-October. The crop may be utilized as pastures from late-October to mid-November.

Table 3. Bird's-foot trefoil stands under different management systems 5 years after sowing (Fergus and Dawn combined).1
Plant Class Hay Management
Plants/square yard
Hay Management
Plants/square yard
Large 9 10
Medium 11 18
Small 0 43
Very Small 0 22
Total 20 93
1 Source--Taylor, et al. 1973. Agron. Jour. 65: 646-648.
2 One crop was permitted to set seed and shatter the 2nd and 4th year of the 5-year study. No seeds were permitted to ripen under hay management.

Lime and Fertilizer Requirements of Trefoil
Lime and fertilizer requirements for trefoil are similar to those of red clover and white clover. The pH should be maintained from 6 to 6.5 and phosphorus and potassium medium to high.

Trefoil Mixtures and Seeding Rates

Prepared Seedbed Sowing in Spring or Late Summer--
Trefoil--6-7 pounds/acre
Tall Fescue--6-8 pounds/acre
Timothy--2-3 pounds/acre
Kentucky Bluegrass--6-8 pounds/acre
Orchard grass--4-6 pounds/acre
Do not seed with small grain nurse crops or other legumes.

Sod-Seeding in Spring or Late Summer--
Trefoil--6-7 pounds/acre drilled into a nitrogen deficient grass sod
Before seeding, be sure to inoculate the trefoil seed with the correct nitrogen fixing bacteria using a sticker agent.

Disease and Insect Pests
The most destructive disease is Rhizoctonia blight, a fungus that spreads in thick, tall stands during hot, humid summer months. Crown and root rots are also important diseases and are caused by a complex of five or more disease organisms. Leaf and stem diseases caused by Stemphylium and other fungi may also damage the crop. The best management practice is to keep the crop short during summer months by grazing or mowing. Fergus trefoil is more persistent in Kentucky than other varieties of trefoil, and it is likely that Fergus is more tolerant of these diseases.
Meadow spittlebug and potato leafhoppers are the primary insects that damage trefoil. Timely harvesting may be adequate for control, but spraying may be necessary under severe conditions.

Other Uses of Fergus Trefoil
In addition to its usefulness in pastures and meadows, bird's-foot trefoil merits further trial and use in the following situations: vegetative cover for improving the nitrogen fertility of mine spoil areas, vegetative cover along highways, especially in limestone soils, and a honey plant when managed so that plants are flowering from early June to mid-September.

Fergus is a U.S. protected variety, specifying that it can be sold as a class of certified seed by variety name only.