burro-fat, (species Cleome isomeris), shrub or small tree of the Cleome genus (of the family Cleomaceae, which is closely related to the mustard family, Brassicaceae), native to southwestern North America, with showy spikes of yellow flowers and gray-green foliage. Burro-fat, up to 3 metres (10 feet) tall, has three-parted, ill-smelling leaves and flowers with four long petals and short green sepals. The flowers begin blooming from the bottom of the spike and produce inflated gray-green capsules that enclose the seeds. Similar woody species are found in Latin America.