Crimson clover - trifolium incarnatum -

In Focus

Other names: Italian clover
Family: Fabaceae (legumes)
Subfamily: Faboideae
Genus: Trifolium (clover)
Species: Trifolium incarnatum (crimson clover)
Thousand grain weight: approx. 3–4 g
Growth height: up to approx. 50 cm
Sowing rate: 30 kg/ha
Number of chromosomes: 2n = 14

Crimson clover is an annual or biennial herbaceous plant that reaches a height of up to 50 cm. It is sensitive to black frost and trampling. The stalk is mostly protruding, or in rare cases flattened and villous. The stalk is up-right and sparsely branched at most. The alternate leaves arranged spirally on the stalk are divided into petioles and lamina. The petiole is 5 to 18 cm long. The lamina is tripartite and especially large for a clover. The hairy pinnae are oval in shape, 1 to 2 cm long and 1 to 1.5 cm wide with a cu-neate base. The edges of the pinnae are slightly ridged, the tip is rounded or slightly crenate. The lower leaves have long stems. The membrane-like stipules continue downwards like a leaf sheath and grow together with the petiole up to threefifths of their length; the free part is green or pur-ple and, depending on the character-istics, either oval, serrate or costate and with protruding hairs. As a legu-minous plant, crimson clover is also able to have a symbiotic relationship with rhizobia that converts atmos-pheric nitrogen into a plant-availa-ble form. The reddish nodules on the roots indicate the active symbiosis.

Origin and history
Crimson clover originally comes from the western Mediterranean region. Its natural distribution extends from the Iberian Peninsula to France, Italy and the Balkans right up to the Bosporus. Initially, it was cultivated on both sides of the Pyrenees range and possibly in northern Italy as well. Today, crimson clover is grown in Europe, northwards to Great Britain and eastwards to the Caucasus. Other areas of cultivation include North and South America as well as Australia and New Zealand. Because of its global use as fodder plant, there are many new appearances whose establishment greatly depends on climatic conditions. Czech Repub-lic, France, Hungary, Chile and the USA have played the most important role in propagating crimson clover. In 2018, Germany had about 76 ha of propaga-tion fields for crimson clover.

Use and yield
Crimson clover is used as forage, either fresh or as hay and silage. It can also be used for grazing; however, heavy trampling and intensive grazing have a negative impact on green manure production as crimson clover has a very low capacity for regeneration.When it comes to harvest, only the first cut is of importance as the subsequent growth is minimal. It can be cultivat-ed as a winter or summer catch crop, and is also suitable for green manure and erosion control in addition to being valuable fodder. It is possible to harvest between 30 and 45 quintals of crimson clover dry matter per hectare, especially when used as a winter catch crop. The root residue mass before winter is 10–12 quintals DM/ha and after winter is 20–25 quintals DM/ha. The protein content of the entire plant is around 26% of dry matter (may vary between 20–30%) and the fibre con-tent is about 19% of dry matter (may vary between 16–22%). In Central Europe, it is occasionally cultivated as silage fodder in areas with a warm and dry spring. Cultivation as pure stand is generally quite rare, although it is an extremely important component in mixtures. This variety is particularly significant as a component in the Landsberger mixture, which consists of Italian ryegrass, winter vetch and crimson clover. This mixture can be used for grazing or fed as silage. Crimson clover is also commonly used as a greening plant in viticulture. In addition to the above advantages for the soil and en-vironment, crimson clover also has a positive effect on the quality of wine.Crimson clover can also be consumed by humans. Roasted seeds and young seedlings (sprouts) are ideal for use in salads. Honeybees use crimson clover for its nectar, which has a sugar content of 31–38%. Every single flower produces 0.03–0.07 mg sugar daily, making it highly sought after by many insect species. The honey yield is 60–140 kg/ha.

Cultivation and advantages
Crimson clover does undemanding in terms of soil, soil preparation and fertilisation. It is primarily cultivated in mixtures with grass, for instance in the Landsberger mixture, and rarely as a pure stand. As a pure stand, crimson clover is sown at around 30 kg/ha 1–2 cm apart on a fine-grained seed-bed. The row spacing is the same as for cereal grains, normally 12.5 or 15 cm. Row spacing of under 10 cm could have a negative impact on individual plant growth.
Crimson clover is particularly non-competitive in mixtures, meaning that the other plants in the mixture often suppress it over time. In addition, it controls the population of cabbage flies and cabbage white butterflies in cabbage and radish. Sowing crimson clover on harvested beds is therefore recommended in certain cases (watch for increases in the nematode population!).
In Germany, the use of crimson clover seeds has drastically increased over the last 5 years. The main reason for this are the greening guidelines, which have set the requirements for subsidy disbursement since 2015 and are a part of the European Union’s Common Agricultural Policy. Crimson clover is an important element of various greening options, which leads to its use as a component in many catch crop mixtures.