Rapistrum

Rapistrum is a small genus of flowering plants in the mustard family (Brassicaceae). It comprises a handful of species of annual or short-lived herbaceous plants that are native to the Old World and have become naturalized in tropical and subtropical regions elsewhere. The genus is typically found in disturbed habitats such as fields, roadsides, and rangelands.

Plants in this genus are generally erect and herbaceous, with leaves that may be simple or pinnately lobed. They produce loose inflorescences of small flowers, each with four petals as is characteristic of Brassicaceae. Flower color is usually yellowish to pale, and the fruits are slender, elongated siliques that dehisce to release seeds as they mature. The overall morphology is adapted to rapid growth in favorable conditions, contributing to their ability to form stands in disturbed grounds.

Rapistrum rugosum is the best-known species and is widely regarded as a weed in agricultural and pastoral systems. It thrives in warm climates and can spread aggressively when conditions permit, sometimes forming dense patches that compete with crops or native vegetation. Its seed bank can persist in soil, allowing reemergence after tillage or disturbance.

Taxonomically, Rapistrum is placed within the Brassicaceae family and the order Brassicales. Beyond weed management considerations, the genus has limited horticultural or culinary use and is mainly of interest to botanists and ecologists studying diversification within Brassicaceae.