Isopyrum biternatum (Syn. Enemion biternatum)

False Rue-Anemone Ranunculaceae

A lovely little North American woodland perennial that deserves to be grown far more widely. Isopyrum biternatum, now generally treated by Kew as Enemion biternatum, is the eastern false rue-anemone: a delicate spring ephemeral forming neat clumps of finely divided, fresh green foliage, above which appear small, pure white flowers in spring. 

Its natural range extends from south-eastern Canada through much of the eastern and central United States, including Ontario and states from New York and Michigan south to Florida and westwards to Kansas, Oklahoma and Texas.  In the wild it is particularly characteristic of rich, moist deciduous woodland, floodplain terraces, wooded stream margins and lower valley slopes. It is often associated with calcareous or lime-rich soils and is frequently found surprisingly close to streams, provided the ground is not subject to prolonged flooding. 

In cultivation, give it light or dappled shade and a fertile, humus-rich, moisture-retentive soil, ideally with a neutral to slightly alkaline reaction. It flowers in spring before retreating underground for summer, making it an excellent companion for later-emerging woodland plants.

Height: 10–30cm
Spread: 20–30cm
Flowering: April–June
Position: Dappled shade to shade
Soil: Moist, fertile, humus-rich, preferably lime-rich
Hardiness: H7, approximately −20 to −15°C