The Japanese anemone (actually three species: Anemone x hybrida, A. huphensis. and A. tomentosa) is among the last perennials to bloom. Indeed, it is only at the very end of August or in September that the many round flower buds, borne on slender branching stems, unfurl to reveal large single or semi-double white, pink or rose flowers. The plant can vary in height from 3 to 5 feet (1 to 1.5 m) for conventional varieties to only 18 inches (45 cm) for some of the recently introduced dwarf cultivars. Its dark green maplelike foliage appears in spring and continues throughout the summer.
Warning! This plant will eventually become invasive through its creeping underground rhizomes. When you first plant it, you’ll have a hard time believing that: it is so slow to really take off, spending 3, 4 or even 5 years in a nice tight clump. But then, off it goes! The saying is: first it sleeps, then it leaps! Do plant your Japanese anemone where you can control its spread… or where its wandering habit won’t be a problem.
Ideally, you should plant your Japanese anemone in partial shade, perhaps in an open woodland or at the forest edge, but it tolerates full sun too… and will grow in shade, although in may not bloom well there. It will grow in any well-drained soil. Once established, it is quite drought-tolerant, but it’s better to water it well the first season until its roots are firmly established.
The typical Japanese anemone does well in zones 5 to 9 and is perfectly hardy in zone 4 if you mulch it well. I just let dead leaves cover it up in the fall and it does wonderfully for me. A. tomentosa ‘Robustissima’ is hardier than others and should be solidly hardy into zone 3.