Birdsfoot Trefoil (Lotus corniculatus)
Bean Family (Fabaceae)
bloom-fell, cat's-clover, crow-toes, deer vetch, devil's-claw, ground honeysuckle, hop o'my thumb, sheep-foot, yellow trefoil.
Origin and Distribution:
This weed was introduced from Europe into North America, possibly as early as mid-1700, where it is still valued as an agronomic crop although it is capable of escaping cultivation and becoming a bothersome weed. Several cultivars are commercially available for planting as ground cover, pasture, hay, and silage. Plants that have escaped cultivation can be found inhabiting large areas in lawns, meadows, and waste places throughout the northeastern U.S. and southern Canada. It is widespread throughout Ohio. Compared with other legumes, the species tolerates a wide variety of moisture conditions and soil types and is frequently found on drought-prone soils that have low fertility. It does not grow well in shade.
Birdsfoot trefoil has a perennial root crown and stems that die back each winter. The species is characterized by compound leaves consisting of 3 clover-like leaflets at the tip separated by a short stem from 2 smaller leaflets at the base. Its flowers are yellow, clover like, and in groups of 2 to 6. They are arranged such that, when pods form, they resemble a bird's foot. Reproduction is by seeds and plants spread by modified stems (stolons) and rhizomes (horizontal underground stems). Because roots arise from buds at the nodes of older stems, it is possible to propagate plants by stem cuttings. Also, new shoots arise from root crowns.
Birdsfoot trefoil produces a long taproot that may extent over 3 feet. Also, a fibrous mat appears near the soil surface as the result of formation of secondary roots, rhizomes (horizontal underground stems), and stolons.
Seedlings and Shoots:
Seedlings are small and slow-growing and do not compete very successfully with other plants.
Many branched stems can emerge from a single root crown and may be either erect or prostrate and up to 3 feet long. The lower portion of each stem is round in cross section, while the upper portion is square. Stems may be smooth or hairy, and can become woody with age.
Leaves are alternate (1 leaf per node) and compound with 5 leaflets. Leaflets are generally oval and less than 1 inch long. At the top of each leaf are 3, clover-like leaflets separated by a short stem from 2 smaller leaflets attached directly to the stem at its base.
Clover-like flowers are about 1/2 inch wide and bright yellow, although they may be streaked with red. Flowers form in groups of 2 to 6 at the end of a long stalk (peduncle) arising from an upper leaf axil. Flower clusters are shaped like flat-topped umbrellas (umbels).
Fruits and Seeds:
Pods are approximately 1 inch long, cylindrical, and brown to almost black. Seeds are 1/20 inch long, rounded or oval, flat, shiny, and olive green to nearly black.
Birdsfoot trefoil is similar in appearance to some clovers (Trifolium species) and medics (Medicago species) except the serrated edges of clover and medic leaflets differ from those of birdsfoot trefoil, which are smooth. All of the yellow-flowering clovers and medics have numerous flowers arranged in a rounded head whereas birdsfoot trefoil has only 2 to 6 flowers grouped in an umbel. Clusters of birdsfoot trefoil flowers give rise to umbel-shaped groups of pods that resemble those of crownvetch (Coronilla varia). However, birdsfoot trefoil can be distinguished by its compound leaves with 5 leaflets, 2 of which are smaller and nearer the base than the 3 clover-like leaflets located at the tip.
Seeds germinate primarily in spring but also in fall. Flowers are produced from late June until frost. On average, 10 to 20 seeds form in each pod. Pods rupture when mature in such a manner that seeds are ejected. Birdsfoot trefoil is a valuable forage crop that will grow under many soil conditions including drought, flood, saline, acidic, and low fertility. It is planted along highway right-of-ways as a ground cover and in pastures to increase productivity. Once established, it tolerates heavy grazing but does not cause bloat in livestock feeding on it. However, it tends to escape cultivation becoming an undesirable weed. Frequent mowing (more than once every 3 weeks) at a height less than 2 inches is required to control birdsfoot trefoil. It can also be controlled by pre-emergence applications of herbicide or by applying selective herbicides to seedlings.
Plants contain toxic amounts of cyanogenic substances. Although reports of poisoning of livestock and humans are lacking, grazing by insect pests may be deterred by the toxin.
Facts and Folklore:
'Birdsfoot' refers to the manner pods attach at right angles to the peduncle giving the appearance of a 'bird's foot'.
Birdsfoot trefoil seeds are one of the most common impurities of white clover seeds as well as some commercially-available grasses.
As most plants in the bean family, birdsfoot trefoil adds nitrogen to soil and for this reason, it is useful for improving poor pasture land.