Bird's-Foot Trefoil

In June, a mowed roadside or the thin edge of a ballfield can turn yellow at ankle height. Look closer and the color breaks into small rings of pea-shaped flowers, three to twelve to a ring, each ring held at the tip of a bare stalk. Some petals are streaked with red, and some flowers deepen to orange. This is bird’s-foot trefoil, Lotus corniculatus.¹

The name promises three leaves, and three leaflets do sit at the tip of each leaf stalk. Count again, though. A second pair sits lower down, right where the leaf meets the stem, and those two are nearly as large as the others.¹ Some sources count them as leaflets, which makes five.² Others call them leaf-like flaps of the kind many plants carry at the base of a leaf.¹ Either way, the plant named for three leaves shows five green blades on every leaf. In Britain, a conservation charity explains the name by noting that the lower two bend back against the stem, so only three seem to stand out.³

The bird’s foot arrives after the flowers. Each flower gives way to a slender pod about an inch long, and the pods spread outward from the end of the stalk like toes.² They ripen from green to brown. Then they split and twist into spirals, throwing out their seeds. Growers who raise this plant for seed can lose 65 to 85 percent of a crop to those twisting pods.² British country names catch both stages: “eggs and bacon” for the yellow and orange flowers, and “granny’s toenails” for the claw-like pods.³

A world plant checklist records bird’s-foot trefoil as native across Europe, around the Mediterranean and North Africa, east through Iran and Central Asia to the Himalaya, and in the highlands of Ethiopia, Kenya and Tanzania.⁴ The same checklist marks it as introduced in parts of North and South America, southern Africa, Australia, New Zealand and East Asia.⁴ The first community record on this page came from Wisconsin on June 30, 2026, inside that introduced range. Later records came from Michigan and from England, where the plant is at home.

It traveled as a crop. Like crimson clover, it belongs to the pea family and has been sown on purpose in fields. Farmers grow it for pasture and hay because it holds tannins that keep grazing animals from bloating, a swelling of the gut that some other pasture legumes can cause.² It was also planted on banks and slopes to hold soil in place. From those plantings it spread. Minnesota Wildflowers now lists it as invasive there, common along roadsides and moving into better habitat.¹ In Illinois it often forms dense colonies that crowd out other plants.⁵

Part of that toughness sits below ground. A deep, branching root lets the plant ride out dry spells, and it grows on shallow, salty, wet or moderately acid soils where alfalfa struggles.² Growers coat the seed with a particular bacterium before sowing, so that small bumps form on the roots and house it.² Those root partners probably add nitrogen to the soil around the plant.⁵

Above ground, long-tongued bees do most of the pollinating.⁵ In Britain and Ireland this is the main food plant for caterpillars of the common blue butterfly.⁶ In Illinois, caterpillars of the orange sulphur feed on the leaves.⁵

One small yellow neighbor causes the most confusion. Black medick has only three leaflets, and its flowers are tiny, an eighth of an inch or less, packed ten to twenty into a round head.⁷ Crown vetch holds its flowers in a similar ring, but they are pink or whitish.⁵

Next time yellow shows up at ankle height, count the blades on one leaf. If you reach five, come back in late summer and look for brown pods spread like toes. A pod that has already curled into an empty spiral has finished its work.