Viola sororia (woolly blue violet, "Amerikasumiresaishin")

Japanese name: アメリカスミレサイシン （亜米利加菫細辛）
Scientific name: Viola sororia

[Overview]
A perennial.
It has no aerial stem.
It has a rhizome that thickens like wasabi.
The leaves are basal, on long petioles, round and heart-shaped, with a glossy upper surface.
The leaf margins have low teeth.
The leaves at flowering time are about 5 cm long, and those that appear after flowering reach as much as 12 cm.
The flowers are borne at the tips of upright flower stalks that rise from the leaf axils; they are 2–3 cm across and deep bluish purple.
The bases of the lateral petals are hairy, and a short, thick spur extends behind the flower.
There are cultivars with different flower colors.
The summer flowers are cleistogamous.
The fruit is a capsule that splits into 3 when ripe and scatters the seeds.

[Cultivation]
Propagate from seed, by root cuttings, or by division.
It prefers a sunny, well-drained soil rich in humus.
For potted plants, water thoroughly when the soil surface dries; for plants in the ground, rainfall is sufficient.
Fertilizer is not particularly necessary.
It is easy to grow, but powdery mildew may occur.
Pests include aphids, spider mites, cutworms and the Indian fritillary (Tsumaguro-hyomon).

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