The Anemone, commonly known as the windflower, is a diverse genus celebrated for its delicate, cup-shaped blooms that offer color across three seasons. This popular plant includes over 200 species belonging to the buttercup family, Ranunculaceae. Whether all anemones are perennial depends entirely on the specific species and the climate in which it is grown.
Understanding the Anemone Genus
The perennial nature of any given Anemone species is determined primarily by the structure of its underground storage organ. The genus is broadly divided into two main categories: those that grow from tuberous roots and those that possess fibrous or rhizomatous roots. Tuberous-rooted species, like the Poppy Anemone, are often treated as tender perennials or annuals because their tubers are sensitive to cold, wet winter conditions. Conversely, the fibrous-rooted types, such as the Japanese Anemone, are reliable herbaceous perennials that spread easily to form colonies.
Perennial Habits of Common Anemone Types
The spring-blooming Anemones are usually the ones that challenge the perennial label in colder regions. The popular Anemone coronaria, or Poppy Anemone, grows from a tuberous rhizome and is reliably perennial only in USDA Hardiness Zones 7 through 10. Outside of these warmer zones, gardeners often treat A. coronaria as an annual, or they must lift and store the tubers indoors over winter. Another spring bloomer, Anemone blanda (Grecian Windflower), grows from a corm and is hardier, naturalizing well in zones 4 through 8, though it still requires well-drained conditions to survive winter dampness.
In contrast, the fall-blooming types are the hardy perennials most gardeners expect. The Japanese Anemone is a fibrous-rooted perennial that thrives in zones 4 through 8. These varieties form dense clumps, often spreading by suckering roots to create large colonies. Similarly, the Snowdrop Anemone (Anemone sylvestris) is a fibrous-rooted species that is cold-hardy, thriving in zones as low as 3. These robust types require minimal intervention and are prized for their late-season display.
Ensuring Successful Overwintering
Successful overwintering requires attention to soil conditions, especially during the dormant season. All types of windflowers demand well-drained soil, as excessive winter moisture is the primary cause of root and tuber rot. Amending heavy soils with organic matter or sharp sand before planting improves drainage significantly.
For spring-blooming, tuberous species planted in borderline hardiness zones, a layer of protective winter mulch is helpful. This insulating layer of straw or compost stabilizes soil temperature and shields the tubers from extreme cold. Tuberous corms should be planted three to four inches deep in the fall for natural insulation. When plants enter dormancy, the foliage should be left in place until it dies back completely. This allows the leaves to gather maximum energy for storage, strengthening the roots for the following season’s growth.