All Thalictrum species are herbaceous perennials with nectarless, apetalous flowers. The sepals are small and inconspicuous in the majority of species while some hermaphroditic species have larger and/or colored sepals. Flowers have numerous stamens that are sometimes the most conspicuous part of the flower. The 1- many pistils are simple and uni-ovulate and the fruits are dry achenes. Hermaphroditic (male and female functions within each flower), dioecious (separate sexes on different individuals) and andromonoecious (male and hermaphroditic flowers on the same individual) breeding systems are found in Thalictrum. Species within the genus vary in their mode of pollination (reviewed in Pellmyr 1995). While dioecious species are often wind-pollinated, and hermaphroditic are insect-pollinated, both types of pollination mechanisms have been reported within each breeding system.
Tamura (1995), in the only complete, modern synopsis of the genus, recognizes 190 species of Thalictrum, a much more precise estimate than the 330 species reported in an earlier publication (Tamura 1993). Thalictrum and seven other genera are classified in Ranunculaceae subfamily Thalictroideae Raf. ( = Isopyroideae Tamura). The subfamily is characterized by small "T-type" chromosomes and x = 7 (Jensen et al. 1995; Ro et al. 1997) and its monophyly is supported in phylogenetic analyses of cpDNA restriction sites (Johansson 1995), nuclear genes (Kosuge et al. 1995; Ro et al. 1997) and a combination of nuclear and plastid genes (Hoot 1995). The ITS region sequence analysis of Ro & McPheron (1997) supports (81% bootstrap) the monophyly of Thalictrum (10 species sampled) and the unrooted topology ((Thalictrum, Leptopyrum,Paraquilegia)),((Dichocarpum,Enemion),Aquilegia)). Thalictrum is the only member of Thalictroideae with achenes (the other genera have follicles). Petals have apparently been lost independently in both Thalictrum and Enemion.