Trefoils
by Bruce Homer-Smith

Trefoils are pea plants with finger-like compound leaves. They’re generally found in the genus Acmispon. Here are several:

Chilean Trefoil (Acmispon wrangelianus) grows low to the ground and has yellow flowers that fade to red. Although the word trefoil implies you’ll find 3-part leaves, this species has compound leaves divided into 4 short-haired, flat, oval leaflets.

Chilean Trefoil – photo Wilde Legard

Chilean Trefoil – drawing Judy Mason

Bird’s Foot Trefoil (Lotus corniculatus) has pea flowers clustered at the end of the stem (different from Chilean Trefoil above). These clusters turn into narrow pea pods which group together to look like a bird’s foot. Leaves tend to have 5, bunched, hairless, flat leaflets.

Bird’s Foot Trefoil – photo Steve Matson

Bird’s Foot Trefoil – drawing Judy Mason

American Trefoil (Acmispon americanus) has a white, pink-veined pea flower. Leaflets are on short stalks, next to the stem. They’re in 3s, fuzzy, and a little longer (>1/2”) than the other trefoils.

American Trefoil – photo Wilde Legard

American Trefoil – © Neal Kramer

Small-Flowered Trefoil (Acmispon parviflorus) is widespread in lower elevations with single, small (<1/4”), cream-colored pea flowers nestling at the base of leaves. Leaf fingers are 3 – 5, pointed at both ends and flat.

Small-Flowered Trefoil

Photo Steve Matson

Small-Flowered Trefoil

Drawing Judy Mason

Short-Podded Trefoil (Acmispon brachycarpus) is widespread and forms a mat on the ground with single, orange pea flowers nestling among the leaves. Vegetative parts are quite hairy. Finger-like leaflets are thick, in groups of 4. Notice the very short pea pods in both pictures below.

Short-Podded Trefoil - Photo Wilde Legard

Short-Podded Trefoil

Drawing Judy Mason

There are about a dozen trefoils in California. You can tell them by their distinctive leaf arrangement and pea flowers

Corrections/Comments: bruce@PlantID.net