Acaena

Acaena is a genus of approximately 60-100 species of perennial, often mat-forming, flowering plants in the family Rosaceae, native to the Southern Hemisphere, primarily Australia, New Zealand, and South America, with a few species found in Hawaii and California. They are commonly known as bidibid (in New Zealand), piripiri (also in New Zealand), and New Zealand burr.

Description:

Acaena species are typically low-growing plants, ranging from creeping groundcover to slightly more upright forms. They are characterized by their pinnate or imparipinnate leaves, meaning the leaves are composed of leaflets arranged on either side of a central stem, often ending in a single terminal leaflet. The leaves are usually green, but some species exhibit bronze or reddish hues.

The flowers are small and inconspicuous, often lacking petals, and are grouped into dense, spherical or oblong flowerheads. These flowerheads are typically green, brown, or reddish.

The fruit is a small, dry achene, often armed with barbed spines or bristles. These spines are responsible for the plant's common names like "burr" as they readily attach to fur, feathers, and clothing, aiding in seed dispersal.

Distribution and Habitat:

Acaena species are predominantly found in temperate and subantarctic regions of the Southern Hemisphere. They thrive in a variety of habitats, including grasslands, coastal areas, alpine meadows, and open woodlands. They are often found in disturbed areas and can tolerate a range of soil conditions.

Ecology:

Acaena plants play a role in various ecosystems. Their dense mats can provide ground cover, helping to stabilize soil and prevent erosion. They also serve as a food source for some herbivores. The barbed fruits are dispersed by animals, contributing to the plant's spread. Certain species can be invasive in regions outside their native range.

Cultivation and Uses:

Some Acaena species are cultivated as ornamental ground cover plants in gardens, valued for their attractive foliage and ability to suppress weeds. They are relatively low-maintenance and can tolerate a range of conditions. However, their burr-like fruits can be a nuisance, and some species are considered invasive in certain regions. Propagation is typically achieved through seed or division.