Arabidopsis, rockcress is a genus of small usually annual flowering plants in the Brassicaceae (mustard family, which also includes cabbage and broccoli). This genus contains thale or mouse-ear cress (Arabidopsis thaliana), which is an important model organism in plant biology and it was the first plant to have its entire genome sequenced, in the year 2000. Members of this genus, especially thale cress, are typically fast-growing and complete their life cycles quickly--from germination and growth to flowering and seed set in 4 to 6 weeks; the short generation times allow genetic changes or manipulations to be easily observed, making it a useful model.

Currently, the genus Arabidopsis has nine species and eight subspecies, based on recent morphological and molecular phylogenies by O'Kane & Al-Shehbaz (1997, 2003) and others. Their findings confirm that the species formerly included in Arabidopsis made it polyphyletic. The most recent reclassification moves two species previously placed in Cardaminopsis and Hylandra and three species of Arabis into Arabidopsis, but excludes 50 that have been moved into the new genera Beringia, Crucihimalaya, Ianhedgea, Olimarabidopsis, and Pseudoarabidopsis.

All Arabidopsis species are indigenous to Europe, while two of the species have broad ranges also extending into North America and Asia. Although many species in the Brassicaceae are edible, Arabidopsis species are not noted as edible plants, and are generally considered weeds due to their widespread distribution in agricultural fields, roadside, and disturbed lands.

(NSF 2012, O’Kane & Al-Shehbaz 1997, O’Kane & Al-Shehbaz 2003.)