As the source of rhubarb and buckwheat, this family also contains many 'weedy' species. Pollen in Paleocene deposits.
Flowers are small and borne in various inflorescence types.
Petals are lacking. Fruit an achene or nut. Seeds are hard with a straight or curved embryo. Placentation is basal. Leaves entire and alternate, opposite or whorled with the base forming a sheath around the stem.