Amoria nigrescens (Viv.) Fourr.
Trifolium meneghinianum Clementi
Trifolium petrisavii Clementi
Common Name: Ball Clover
Trifolium nigrescens is a prostrate to erect, annual plant producing a root-crown rosette of stems 75 - 100cm long[
The plant is sometimes cultivated in soil improvement and stabilization projects.
All around the Mediterranean, east to the southern Caucasus, Iran and Iraq
Found in a vaiety of habitats; at elevations up to 1,200 metres.
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Trifolium nigrescens is a plant of the Mediterranean region with its moist to wet winters and hot, dry summers, where it is found at elevations up to 1,000 metres. It grows best in areas where annual daytime temperatures are within the range 16 - 22°c, but can tolerate 10 - 26°c[
]. When dormant, the plant can survive temperatures down to about -4°c, but young growth can be severely damaged at 0°c[
]. It prefers a mean annual rainfall in the range 1,000 - 1,200mm, but tolerates 620 - 1,330mm[
]. The plant germinates with the onset of wet weather, growing through the winter then flowering, setting seed and dying with the onset of hot, dry weather[
Grows best in a sunny position, but can tolerate light shade[
]. Succeeds in most soils, preferably well-drained, though can take occasional inundation of the soil[
]. Responds to good soil fertility[
]. Prefers a pH in the range 5.5 - 6.5, tolerating 5 - 7[
The plant begins spring growth later than most other annual clovers with essentially all the forage production occurring in mid to late spring[
The white to yellowish white flowers are fragrant[
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[
The plant is cultivated as a soil improver and stabilizer[
Seed - the seed of Trifolium species is often of two kinds - hard-coated and soft-coated. The soft-coated seeds can germinate immediately, whilst hard-coated seeds remain dormant until the seedcoat has broken down enough to permit the ingress of water. In order to speed up and improve germination rates, hard-coated seeds benefit from scarification before sowing. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. The seed can usually be sown in spring in situ.
If the seed is in short supply, it might be better to sow it in pots in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and plant them out after the last expected frosts.
A shallow sowing depth, 8-12 mm, is optimal with a light but firm soil cover[