Trifolium incarnatum L.
Crimson clover, Italian clover, French clover.
Dr. John Frame
Pubescent annual, semi-erect to erect growing with a crown rosette of very hairy stems, 0.3-0.6 cm, which have few side branches. Leaves broad and round- tipped; stipules rounded with purple edging developing with age. Tap-rooted with many finely-branched lateral roots. Inflorescences are terminal conical racemes up to 5 cm long and some distance above last stem leaf. Florets, 75-125 in number, are rich crimson, self-fertile. Pollination by bees; fruit contains a single seed. Calyx covered with stiff hairs. Seeds oval to spherical, 2.5 mm long, and cream to light brown in colour. After seed maturation of three to four weeks, the plant dies.
Native to southern Europe where grown as a winter annual for forage. Grown in moist winter areas of south-eastern and Pacific-coastal USA for cool-season growth (Knight, 1985a). Has non-agricultural use to stabilise and beautify steep banks and roadside verges. Can also be used as a summer annual for green manure in cooler northern latitudes (Hoveland and Evers, 1995). Used as a high-quality forage for hay or silage in high-rainfall regions of southern Australia.
Adapted to a wide range of soil and climatic conditions more so than other annual forage legumes though not to poorly-drained or saline soils. Vigorous seedling growth. Not tolerant of shade.
Season of growth
Strong late autumn and winter growth. Matures in early spring.
Not a winterhardy species (though more so than arrowleaf and rose clovers).
Tolerance of flooding
Target soil pH 6.0-7.0 (PLANTS database, 2000). Will grow on soils of low fertility but benefits from good soil P status. Subject to Fe chlorosis on strongly alkaline soils.
The correct strain of Rhizobium leguminosarum bv. trifolii should be used for seed inoculation prior to sowing onto land which has no history of growing crimson clover.
Ability to spread naturally
Because of the high production of soft seed and rapid softening of hard seed, germination of seed can occur in summer rather than in the autumn, thus limiting optimal, timely self-reseeding (Hoveland and Evers, 1995).
Land preparation for establishment
Well-cultivated, uniform and firm seed bed required for best results. Direct drilling (sod seeding) most successful on swards with low-density vegetation and when there is adequate soil moisture.
Can be conventionally broadcast or drilled in well-prepared seed beds. Can also be direct drilled (sod seeded), following close defoliation of the sward, into perennial warm-season grass swards e.g. bahia grass, Bermuda grass (Dunavin, l982; Overman et al., l992).
Sowing depth and soil cover
The optimum sowing depth is 8-12 mm with a light but firm soil cover.
Sowing time and seed rate
Sown in late summer-early autumn when pure-sown, and up to early winter for oversowing warm-season grass swards. The seed should be sown early enough for sufficient seedling development to withstand winter conditions. May be frost-seeded in late winter for summer growth. Seed rate 10-20 kg/ha with the lower rate used when sown in mixture with grass. For seed production, 8-10 kg/ha.
Number of seeds per kg
310 000 to 330 000.
Percentage hard seed
Variable according to cultivar, since some cultivars have been developed for hard seed characteristic.
Compatibility with grasses and legumes
Compatible with grasses such as bahia grass and Bermuda grass.
Strong vigour and rapid early growth. Based on seedling development, namely, leaves, nodulation, shoot weight, root weight, root length and LAI, crimson clover had the highest values in comparison with arrowleaf and rose clovers (lowest values) and subterranean clover (intermediate) (Evers l999).
Vigour of growth and growth rhythm
Vigorous autumn and winter growth which continues into spring (Pedersen and Ball, l99l).
A pure-sown stand fixed 155 kg N/ha (Brink, l990). If used as green manure, maximum herbage N (70 kg/ha) achieved at late-bloom stage (Ranells and Wagger, l992).
Response to defoliation
Poor regrowth after grazing. Close grazing should be avoided in winter so as not to affect spring growth or seed production adversely. Calyces are covered with stiff hairs which may cause digestive upsets if sward grazed during flowering.
Pollinated by bumble bees and honey bees. Chromosome number 2n = 2x = 14.
Dry matter yields
Yields of 3-6 t/ha of hay achieved in the USA when plant development at the pre-50% bloom stage (Hoveland and Evers, l995). Under a Mediterranean environment and using an ecotype (Campano), three-year averages were 1.99 and 3.65 t/ha for pure-sown swards, unirrigated and irrigated, respectively, and 4.71 and 6.33 t/ha for an Italian ryegrass/crimson clover mixture, unirrigated and irrigated, respectively (Martiniello, 1996).
Suitability for hay and silage
Suitable for hay and silage. Hay cut at mature stage of growth can be harmful to livestock since hairs of stems and flowerheads have become hard and tough.
Highly acceptable forage for grazing, silage or hay (though not at mature hay stage).
Protein-rich forage especially at leafy growth stage.
In specialist seed-growing areas in Oregon, USA 600-900 kg/ha achieved, but yields are much lower in south-east.
Seed quality standards
In general, a seed purity of 98% and viable seed of 85% desirable.
Some examples from the USA are Au-Robin, Aulaga, Chief, Dixie (the most commonly sown), Flame, Talladega and Tibbee. Caprera is a cultivar used in southern Australia.
Clover rot (Sclerotinia trifoliorum) is the most serious disease. Spread and subsequent plant loss can be rapid in dense swards during wet winters. Other potential diseases are Phytophthora foot rot (Phytophthora megasperma), Fusarium wilt (Fusarium oxysporum), Fusarium root rot (Fusarium spp.).
Susceptible to a number of viruses.
In the USA, insects which affect young stands include army worms (Spodoptera frugiperda) and S. ornithogalli. The clover head weevil (Hymenia meles) and lesser clover weevil (H. nigrirostris) attack the seed heads, reducing seed yields (Hoveland and Evers, l995).
Vigorous establishment phase and high forage production. Adaptability to a wide range of soils. Early maturity makes it highly suitable for no-tillage rotations e.g. with maize (Holderbaum et al., l990).
Poor self-reseeding ability because of lack of production of hard seed. Seedlings susceptible to various species of insect pests. Susceptible to several diseases. Risk of bloat.