| + | Leaves bi- to tripinnate with minute or wanting stipules: fis. dioecious, small; calyx 5-lobed petals 5; stamens many; pistils commonly 3: the follicles dehiscent, glabrous, usually 2-seeded; seeds minute, dull.— Two species in N. Amer., N. and W. Eu., N. Asia to Japan. Formerly usually referred to Spiraea, which differs chiefly in its shrubby habit, simple, rather small Lvs., and 5 pistils. |
| + | They are tall perennial herbs with large compound leaves and small white flowers in slender spikes forming large terminal panicles. The species in cultivation is hardy North; it prefers rich rather moist soil and grows well in half-shady situations. Propagation is by seeds, which germinate readily, and also by division of older plants. |