[Overview]
An evergreen perennial or subshrub.
The leaves are opposite or whorled.
The flowers are borne 1–2 at a time in the leaf axils, and are yellow, pale bluish purple, white and so on.
The corolla is deeply 4-lobed and opens flat, and fine hairs of the same color as the flower grow densely in the center.
There are 4 stamens.
The sepals are 4-lobed.
The fruit is a capsule.
[Cultivation]
Propagate by division.
Because it is vulnerable to cold, in Japan it is mainly treated as an annual, but it can overwinter in warm regions without frost.
It prefers a sunny, well-drained soil.
For potted plants, water thoroughly when the soil surface dries; for plants in the ground, rainfall is sufficient unless sunny weather continues and the soil dries out.
When overwintering, keep it somewhat on the dry side.
During the growing season, apply slow-release fertilizer or liquid fertilizer.
There are no particular pests or diseases.
