Fatoua villosa aka Hairy Crabweed

Fatoua villosa has two names: mulberryweed and hairy crabweed. It is part of Moraceae, the mulberry family. Its native range starts in Thailand. It reaches central and southern Japan and northern Australia. It also grows outside that range in the United States. Louisiana first recorded it in 1964. It now grows across much of the southeast and elsewhere.

This herb grows fast, with upright stems that branch. Its growth is dense. One source gives a height of about 2.3 feet [0.7 metres]. That source also reports plants reaching 3.3 feet [1 metre]. Most accounts call it an annual, which lives one year. Useful Tropical Plants also records plants that live for years. These perennial plants have stems with some woody parts. Green stems bear hooked hairs. Both stems and leaves feel hairy and sticky. Simple leaves grow one by one on alternate stem sides. They feel thin and papery, with teeth along their edges. Their shapes range from triangles to hearts. Young plants can look like mulberry seedlings. Their hairy stems help tell them apart.

Flowers bloom from late spring into early fall. Small male and female flowers share dense groups called cymes. These grow where leaves join stems. Flowers are pale green, but young groups can look purple. Old groups turn dark brown. Lower and middle groups tend to have more female flowers. Upper groups hold more male flowers. The small, white, oval fruit is an achene with three angles. Plants shoot seeds at least 4 feet [1.2 metres] away. Seedlings can flower and fruit within 12 days of reaching two leaves. Seeds sprout from early spring into late fall. This lets several generations grow in one growing season.

NC State lists shade, filtered light, and part shade as suitable. It lists moist or sometimes wet soil, including clay and loam. Acid to neutral soil suits this plant. Its listed USDA range is 5a–11a, but frost kills annual plants. In the wild, it grows in dry scrub and grassland. It also grows on walls, rocky ground, and cliffs. It forms low, dense growth where trees grow sparsely. Its main garden problem is fast spread, not pests or disease. It infests greenhouses and disturbed ground. Some US states list it as invasive. NC State stresses keeping sites clean as part of control.

People gather wild plants for use in traditional medicine. Reported root uses include fever and problems with passing urine. They also include problems with menstrual periods. Leaves have served as a folk remedy for stomach pain. These are past uses, not proven treatments. Useful Tropical Plants lists no known food uses. Its hazard summary lists no hazards. Yet its full account reports phototoxic compounds in root extracts. These can harm skin when sunlight follows contact. This evidence does not show safety for people or pets.