lesser yellow trefoil, little hop clover, yellow suckling clover
Trifolium dubium Sibth. (Chrysaspis dubia)
Lesser trefoil is procumbent winter or rarely summer annual found in grassy places and open ground. It is common throughout Britain and is recorded up to 1,600 ft. Two distinct forms occur, one found in open habitats on cinders and spoil, the other on grassland sites, waysides, wasteland and on lawns.
Lesser trefoil flowers from May to June in dry sites and from May into October in moist sites. The flowers are self-pollinated. Seeds ripen 1 month after flowering. The seeds exhibit hard-coated dormancy.
The main period of emergence is June to October with odd seedlings appearing at any time of year.
Lesser trefoil forms a persistent seedbank. Seeds have been recorded in large numbers in the soil beneath pasture even though the plant was poorly represented in the vegetation. Seed buried in mineral or peat soil and left undisturbed retained viability for 20 years but only at a very low level. Seed stored under granary conditions had 44% viability after 1 year and 1% after 20 years.
Lesser trefoil seed has been a frequent contaminant in crop seed.
In lawns it survives mowing by developing a low growth habit. On grazed sites this is less successful and it is not a common weed in pasture.
Updated October 2007.