Trifolium.
Family Fabaceae > Subfamily Faboideae.
Plants of the World Online (Kew) lists 299 accepted species.
Australia has around 40 species that are naturalised.
Commonly grown as a pasture crop they are now common in lawns.
They are annual or perennial herbs with prostrate stems.
Off the prostrate stems are erect to semi-erect ones.
There may be hairs.
Leaves are on a petiole with a pair of large stipules at the base.
Stipules are often green and herbaceous.
Their bases are joined forming a ring around the stem and partly sheathing it.
The sides are partly fused to the petiole and the upper edge is smooth or toothed.
The blades usually have 3 (5 – 9) leaflets.
They may be off a short blade midrib (pinnate) or all attached to the top of the petiole (palmate or digitate).
Leaflets may have a smooth edge but usually have teeth.
The many close roughly parallel veins each run up to a tooth.
Axillary, or occasionally terminal inflorescences are mostly a head, spike or umbel.
They may be on a peduncle or directly attached to the stem.
Inflorescences are raceme-like with the lower flowers opening first.
The flowers are directly attached or on a pedicel up to 6 mm long.
There may be no bracts or small ones at the base of the inflorescence.
Bracts are sometimes fused to form an involucre.
The tubular or bell-shaped calyx has 5 (10) teeth or lobes on the rim.
The lobes may be similar or unequal and sometimes they form 2 lips.
There may be callus or hairs at the top of the tube (mouth).
The calyx may remain on the fruit and become larger and inflated.
There are the usual 5 pea-flower petals in white, pink, purple or yellow.
The standard petal may be erect or folded down around the wings and keel.
The claws of the paired wing and keel petals are about half the petals length.
The claw bases on the wings and keel may be free or joined to form a tube.
The 4 claws may be fused to the stamen tube or the base of the standard.
Petals usually remain on the fruit.
Nine of the 10 stamens are mostly fused into a tube with the upper stamen being free or fused.
The short free ends of the filaments curve up slightly.
The small ovary may be on a short stipe or stalk.
The single locule has 1 to 12 ovules.
The sightly curved style has a small stigma that is spherical or just a dot at the tip.
The fruit are pods with the calyx and sometimes the other flower parts attached.
The linear to ovoid pods have 1 or 2 (or more) variously shaped 1 to 2 mm long seeds.
J.F.
