Rhus is a genus of approximately 250 species of flowering plants in the family Anacardiaceae. They are commonly called sumac or sumach. Some species (including Poison ivy, poison-oak, and poison sumac), often placed in this genus, are here treated in the genus Toxicodendron, which differs in highly allergenic foliage and grayish-white fruit but is not genetically distinct. The name derives from the Greek name for sumac, rhous.
They are shrubs and small trees growing to 1-10 m tall. The leaves are spirally arranged; they are usually pinnately compound, though some species have trifoliate or simple leaves. The flowers are in dense panicles or spikes 5-30 cm long, each flower very small, creamy white, greenish or red, with five petals. The fruit form dense clusters of reddish drupes called sumac bobs.
Sumac propagates both by seeds, which are spread by birds and other animals through their droppings, and by new sprouts from rhizomes, forming large clonal colonies.