Birdsfoot trefoil as a forage legume
Birdsfoot trefoil is a long-lived perennial legume well suited to many grass-legume pastures in Missouri. One of its greatest advantages is that it continues to grow and produce forage during mid-summer (July and August), when most cool-season grasses slow or become semi-dormant. Unlike many other legumes, birdsfoot trefoil does not cause bloat, making it a valuable and safe option for grazing livestock.
When combined with cool-season grasses, birdsfoot trefoil can dramatically increase pasture productivity. Trefoil-grass mixtures can produce up to three times more forage than unimproved grass pastures. Even heavily fertilized grass pastures typically produce one-third less beef per acre than grass-trefoil combinations.
Summer forage production and animal performance
Forage produced during the critical summer period (May 17–August 18):
- Grass plus nitrogen: 340 lb dry matter/acre
- Grass plus birdsfoot trefoil: 3,545 lb dry matter/acre
Daily gain of steers on pasture (Iowa State University, Albia Research Station):
- Unimproved pasture: 1.18 lb/day
- Grass plus nitrogen: 1.20 lb/day
- Grass plus birdsfoot trefoil: 1.70 lb/day
These results highlight trefoil’s ability to increase both forage availability and animal gains during summer.
Benefits of birdsfoot trefoil include:
- Improved summer forage distribution
- Greater animal performance
- Greater pasture resilience during dry periods
Approximately 60 percent of trefoil’s annual forage production occurs between June and August, a critical period for Missouri grazing systems.
Region of adaptation
Birdsfoot trefoil will grow throughout Missouri but tends to be most persistent in northern and central regions. It performs especially well on Shelby-Grundy and similar soils. It has been less successful on flat soils with poor internal drainage, such as Putnam and Mexico soil types, where root rot and other diseases are more common.
Trefoil tolerates acidic and low-fertility soils better than alfalfa and most clovers, but not as well as annual lespedeza. However, performance improves significantly as soil conditions improve.
Primary use
In Missouri, birdsfoot trefoil should be used primarily as a pasture legume. It is generally not recommended as a hay crop because:
- It yields less than alfalfa or clover when harvested for hay
- Cutting can weaken or damage stands
- Repeated defoliation increases disease risk Trefoil performs best under managed grazing systems.
Establishment guidelines
Birdsfoot trefoil is no more difficult to establish than other forage legumes, but it requires careful management during the seedling stage. During the first 60-90 days, seedlings are slow-growing and easily outcompeted by weeds or aggressive grasses.
Seeding time
- Late winter or early spring (February-early March) is preferred
- Late spring seedings may require herbicides for weed control
- Fall seedings (before September 1) reduce weed pressure but carry higher risks from drought, insects, winter kill, and heaving
Seeding rate
- Recommended rate: 4-5 lb/acre
- One pound equals approximately 10 seeds per square foot
- A full stand is approximately 5 plants per square foot
Managing competition during establishment
Successful establishment depends on reducing competition for light and moisture. Recommended strategies include:
- Use a pre-emergent herbicide where heavy weed pressure is expected
- Use a small-grain nurse crop, closely grazed or clipped
- Band-seed trefoil into a rough seedbed with 50-100 lb P₂O₅ beneath the seed
- Avoid planting with aggressive legumes such as alfalfa or red clover
- Do not apply nitrogen fertilizer during establishment, as it favors weeds and grasses
Trefoil performs best at a soil pH of 5.5 or higher, though it will tolerate lower pH better than most legumes.
Fertility and inoculation
Birdsfoot trefoil responds strongly to phosphorus and potassium, but nitrogen is unnecessary and often harmful.
- Lime soils to a pH of 5.5-6.0
- Apply phosphorus at seeding (banding is especially effective)
- Broadcast and incorporate potassium prior to seeding
- Top dress established stands annually with 0-30-60 or 0-30-90
- Never apply nitrogen to trefoil or trefoil-grass mixtures
Inoculation
Proper inoculation is essential. Birdsfoot trefoil requires a specific rhizobium bacteria. Store inoculant in a cool place and apply just before planting.
Varieties
- Dawn – Developed at MU; more disease-resistant and persistent, especially in central and southern Missouri
- Empire – Performs well in northern Missouri
- Carroll – Large-seeded variety with strong seedling vigor; well suited to northern Missouri
Companion grasses and seeding mixtures
Tall fescue, orchardgrass, timothy, and Kentucky bluegrass are all suitable companion grasses for birdsfoot trefoil. Sod-forming grasses such as bromegrass are more competitive and may require more careful management.
Seeding mixtures (per acre)
- 5 lb birdsfoot trefoil plus:
- Timothy (2 lb) + Kentucky bluegrass (1 lb), or
- Orchardgrass (3 lb) + Kentucky bluegrass (1 lb)
- Tall fescue: 5-8 lb (avoid heavier rates)
- Bromegrass: 5-6 lb, with careful grazing management Avoid adding other legumes to trefoil mixtures.
Grazing management
Birdsfoot trefoil must be managed differently than alfalfa. Unlike alfalfa, trefoil does not replenish root reserves during summer. It relies on remaining leaf area to fuel regrowth until fall.
Key grazing principles:
- Use controlled continuous grazing, not complete defoliation
- Never remove all leaf material
- Avoid summer stockpiling or hay harvest
- Allow fall rest from September to mid-October
Maintaining productive stands
To maintain long-term trefoil stands:
- Allow periodic reseeding
- Keep plants in a vigorous, leafy condition
- Avoid stockpiling and deferred grazing
- Manage weeds through grazing, mowing, or labeled herbicides Trefoil stands benefit from occasional seed set to maintain a soil seed bank of hard seed.
Disease management
Root and crown diseases are the most damaging threats to trefoil persistence, especially in southern Missouri.
Best management practices include:
- Plant disease-resistant varieties (e.g., Dawn)
- Avoid rapid or complete defoliation
- Prevent excessive shading by companion grasses
- Allow fall rest for root energy storage
Healthy, actively growing plants are far less susceptible to disease.
Seed production
Birdsfoot trefoil seed production can be profitable in Missouri, particularly in northern regions. Typical yields range from 40 to 120 lb/acre, with good years averaging about 100 lb/acre.
Seed production is favored by:
- Sunny days, cool nights, and dry weather from mid-May to July
- Timely harvest before excessive shattering
Birdsfoot trefoil requires bee pollination, and seed yields improve when honeybee colonies are placed near fields.
To estimate yield before harvest: One unshattered pod per square foot equals approximately 1 lb of seed per acre.
Summary
Birdsfoot trefoil is best suited for grazing systems that need reliable summer forage without bloat risk. It performs especially well in northern and central Missouri on moderately drained soils and fits operations that emphasize pasture-based gains rather than hay production. When properly established and managed, trefoil-grass pastures can greatly increase summer forage availability and improve animal performance compared with grass-only or nitrogen-fertilized pastures.
Successful trefoil stands depend more on management than inputs. Establishment requires careful control of competition, proper inoculation, and patience during the slow seedling phase. Once established, trefoil thrives under controlled continuous grazing that maintains leafy growth and avoids complete defoliation. Systems that rely heavily on haying, summer stockpiling, or aggressive companion grasses are more likely to experience stand decline.
Producers should think of birdsfoot trefoil as a long-term pasture investment rather than a short-term yield crop. Allowing occasional reseeding, maintaining soil fertility (especially phosphorus and potassium), and providing fall rest are key to persistence. When these principles are followed, birdsfoot trefoil can be a durable, high-value legume that fills the midsummer forage gap and supports consistent livestock gains.
The authors wish to thank Joe D. Baldridge for his guidance and contribution in preparing the manuscript for this publication.