Trifolium resupinatum

Cultivation Details

Trifolium resupinatum is a plant of the temperate to subtropical zones, growing at elevations up to 1,500 metres. It grows best in areas where annual daytime temperatures are within the range 13 - 22°c, but can tolerate 3 - 26°c^[1]. When dormant, the plant can survive temperatures down to about -12°c, but young growth can be severely damaged at -1°c^[1]. It prefers a mean annual rainfall in the range 600 - 900mm, but tolerates 300 - 1,360mm^[1]. Grows best in a sunny position but toleratis light shade^[1]. Prefers a heavy soil but succeeds in a wide range of soils^{[1, 2]}. Thrives on wet, heavy soils in low areas^[3]. Tolerant of moderately saline soils^[1]. Prefers a pH in the range 6 - 7, tolerating 4.8 - 8.2^[1]. The plant has been widely grown as a forage and green manure crop, especially in Asia, though cultivation has also spread to America, Europe, northern Africa and Australia. Cultivars had been released in European countries, the USA and Australia. When sown in the autumn in mild winter areas the plant can produce a good bulk of green manure by early spring, flowering in mid spring and fruiting in late spring^[3]. Recorded green manure yields are about 40 tonnes per hectare, whilst seed yields are from 150 - 300 kilos per hectare^[3]. The species is very variable: var. minus Boiss., is the wild form, whilst the cultivated ones are var. resupinatum and especially var. majus Boiss.^[3]. The plant has pink-mauve, sweet-smelling flowers, ovoid pods and pale brown seeds^[1]. This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby^[4].