Trifolium microdon, commonly known as thimble clover, is an annual herb native to a variety of habitats in western North America, including grasslands, meadows, and open woodlands, from British Columbia to southern California. It often occupies disturbed areas, which can include roadsides and fields. Thimble clover typically forms decumbent or erect stems that can reach up to 20 inches (50 cm) in height. The trifoliate leaves are composed of oval leaflets, and the plant is distinguished by its inflorescence, which is a dense head of small, white to pink flowers. These flowers are subtended by a bowl-like involucre of bracts, giving the appearance of a thimble, hence the common name.

Thimble clover is valued for its ability to fix nitrogen in the soil, making it beneficial for soil health and useful in restoration projects. It is also appreciated for its delicate flowers, which can add a subtle charm to wildflower gardens and meadows. In cultivation, it prefers full sun to part shade and tolerates a range of soil types, provided they are well-drained. While it is not commonly used in formal garden settings, it can be a component in native plant gardens and as a cover crop in agricultural settings. Thimble clover is relatively low-maintenance, but it can be susceptible to root rot in poorly drained soils. It is also a host plant for various butterfly species, contributing to local biodiversity.CC BY-SA 4.0