Desmodium, also known as tick-trefoil, is a genus of plants in the legume family, Fabaceae, with many species found across the globe. These plants are characterized by their trifoliate leaves, small, pea-like flowers, and distinctive lomentaceous fruits that often have hooked hairs (uncinate trichomes) causing them to stick to clothing or fur. They are known for their nitrogen-fixing abilities, making them valuable for soil health and as forage crops. 

Here's a more detailed description:

General Characteristics:

Growth Habit:

Desmodium species can be annual or perennial, with some being prostrate and creeping, while others are more erect and can grow up to several feet tall. 

Leaves:

They have compound leaves with three leaflets (trifoliate). The leaflets can vary in shape and size, but are often ovate or elliptic, and can have a silvery or hairy appearance. 

Flowers:

The flowers are small, pea-like, and can be white, pink, purple, or lilac. 

Fruits:

Desmodium produces lomentaceous fruits, which are segmented pods that break apart easily at the joints. These pods often have hooked hairs (uncinate trichomes) that allow them to cling to animals and clothing, hence the common names "tick-trefoil" or "beggar lice". 

Roots:

Desmodium plants typically have a well-developed root system, and some species are known to root at the nodes of their stems. 

Habitat:

They are found in various habitats, including meadows, open woodlands, roadsides, and disturbed areas. 

Specific Examples:

Desmodium gangeticum:

A stout herb with angled, hairy stems, used as a substitute for liquorice and as a febrifuge. 

Desmodium intortum:

A large, perennial forage legume with long, trailing stems and trifoliate leaves. It is known as greenleaf desmodium or beggarlice. 

Desmodium triflorum:

A creeping, hairy species with three-parted leaves and small, three-flowered inflorescences. 

Desmodium uncinatum:

Also known as silverleaf desmodium, it is characterized by its prostrate to ascending growth habit and hairy stems with hooked hairs. 

Desmodium Golden Legume:

A cultivar with golden-yellow leaves and legume-shaped flowers. 

Ecological Importance:

Nitrogen Fixation:

Desmodium species are known for their ability to fix nitrogen in the soil, enriching the soil with this essential nutrient.

Forage Crop:

Many Desmodium species are used as forage crops for livestock due to their high nutritional value.

Soil Improvement:

Their ability to fix nitrogen and their dense growth habit can help with soil stabilization and weed suppression.