Trifolium incarnatum L.

Soil Improvement (Green manure)
Soil Protection (Cover Crop)

Herbaceous winter annual legume with an erect growth habit. Often sown in mixtures with other legumes, cereal grains, or annual ryegrass.  Crimson clover is used for pasture or hay, as a green manure or cover crop in rotation with vegetables or field crops, as a reseeding cover crop between rows in vineyards, berries, and fruit and nut orchards. It is a source of pollen and nectar for pollinators.


Life cycle: 
Winter annual
Growth Season: 
Identification Characteristics: 

Inflorescence is a cylindrical or conic flower head 1-2 1/2 inches (2.5-6.5 cm) long containing many small (1/2 inch, 1.3 cm) bright scarlet (or occasionally white) florets that open in succession from the bottom to the top of the head. Plants are densely hairy. Unbranched stems reach 1-3 feet (30-90 cm) tall. Trifoliate leaves are palmately trifoliolate, with egg- to heart-shaped leaflets 1/2 to 1 inch (1.3-2.5 cm) long, finely toothed near the tip. Stipules are elliptic, blunt, violet-veined, reddish-tipped, and mostly fused with the stem. Taproot and numerous fibrous roots extend 12-20 inches (30-50 cm) deep. Seeds are yellow and borne singly in small pods. Seeds are larger and more rounded than red clover seed, with approximately 120,000 to 150,000 seeds per pound (264,000-330,000/kg).

Growth Habit and Production

Growth Habit and Persistence: 

Erect growth habit. Winter annual or summer annual in northern portions of the USA.

Production Profile: 

Seasonal growth is affected by temperature and precipitation. Early maturing species used in pasture systems based on warm-season perennial grasses.

Vegetative growth and forage availability by month have been stylistically drawn in various publications, with zones based on average annual temperature.  Crimson clover is shown here in comparison to other appropriate species for Zone A in the southeastern region of the USA, corresponding to northern Florida to southern South Carolina (mean annual temperature > 65°F, 18°C) (Ball, Hoveland, Lacefield, 2007. Southern Forages. 4th Ed. International Plant Nutrition Institute. 322 pp. ISBN 0-962-9598-6-3).

Zone A - Forage Availability

Climate and Soil Suitability Zones

Climate Tolerances: 

Crimson clover is a winter annual widely grown from Kentucky southward and from eastern Texas to the Atlantic Coast (USDA Hardiness Zones 6-9) and in the Pacific Northwest and California, or as a summer annual in the extreme northern US and parts of Canada (Hardiness Zones 3-4). It does not tolerate drought conditions, and requires 30 inches (760 mm) of rainfall during the growing season. Does not tolerate extreme heat or cold, with optimal growth in cool, humid conditions.

Soil Tolerances: 

Grows on poorer soils than most other clovers. Tolerates strongly acid to moderately alkaline soils (pH 5.1-8.4). Grows best on well-drained, fertile, loamy soils, but tolerates excessively drained to moderately well-drained soils. Tolerates only brief periods of flooding. Once established, it produces more biomass at lower temperatures than most other clovers.

Quantitative Tolerances: 

Crimson Clover Suitability Tolerance Values

Suitability Class

Ave Ann Extreme Min (°C)*

July Max


Annual Precip (mm)**

Soil pH***

Soil Drainage 

Soil Salinity (dS/m)#








Moderately suited







Marginally suited







*USDA Plant Hardiness Zones 6-9 as a winter annual in the southeast; Zones 3-4 as a summer annual in northern US and Canada.

Latitude and longitude delimitations: winter annual – 38 degrees N, 96 degrees W; summer annual from 40-50 degrees N.

** Precipitation requirements: 30 inches (760 mm during the growing season).

Rooting depth: 20 inches (50 cm).

*** Soil pH tolerance: NRCS Range and Pasture Handbook, Chapter 3 classification for crimson clover is strongly acid to moderately alkaline (5.1-8.4). pH. Y=101.3*EXP{-0.5*[(x -6.71)/1.059]2};R2=0.99 Optimum is 6.7. Minimum is 2.16, maximum is 11.26.

† Soil drainage: NRCS Range and Pasture Handbook, Chapter 3 classification for alsike clover is WD-PD. Soil drainage class abbreviations: 1=VPD, very poorly drained; 2=PD, poorly drained; 3=SPD, somewhat poorly drained; 4=MWD, moderately well drained, 5=WD, well drained; 6=SED, somewhat excessively drained; 7=ED, excessively drained. Percent relative yield for crimson clover for the 7 classes: 7, 25, 50, 80, 100, 80, 50. Y = 96.66*EXP{-0.5*[(x - 4.986)/1.75)] 2}; R2 = 0.99.

# Soil salinity tolerance: NRCS Range and Pasture Handbook, Chapter 3 classification for clovers (alsike, Berseem, white, red, strawberry) is moderately sensitive (1.5-3 DS/m). Y=100.23 - 7.61 x - 2.84 x2 (R2 = 0.99).  Y=0, X=4.75.




Quality and Antiquality Factors

Quality Factors: 

Highly nutritious forage, over 25% crude protein that can be 80% digestible in early spring growth, and even at full bloom may contain 12-14% crude protein and 60-65% digestible nutrients on a dry matter basis.

Anti-quality Factors: 

Use in mixtures with grasses to reduce risk of bloat. Bloat much less likely in animals grazing crimson clover than white clover or alfalfa. Flower heads on overly-mature crimson clover are problematic for horses, harvest hay promptly as it begins to bloom.



Cultivars 'Dixie,' 'Autauga,' 'Auburn,' 'Chief,' and 'Kentucky' were developed to self-reseed and have a high proportion of hard seed which is preferred for non-irrigated fall plantings. Early-maturing cultivars are best for over-seeding on summer grass sod to avoid competition, and also for green manure crops to allow early spring termination. Late cultivars have higher yields and can be grazed longer in the spring.

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