Oxypetalum coeruleum

Japanese name: ブルースター
Scientific name: Oxypetalum coeruleum

[Overview]
An evergreen climbing perennial about 60–100 cm tall.
It is not very cold-hardy, so in cold regions it is treated as an annual.
The whole plant is covered with white hairs.
White latex comes out when the stem or leaves are damaged.
The stem extends like a vine.
The leaves are simple and opposite, oblong-heart-shaped, 5–10 cm long, and entire.
Cymes arising from the leaf axils and stem tips bear one to several flowers.
The flowers are pale blue, 2.5 cm across; the corolla is deeply 5-lobed with a short tube.
They are tinged with pink as buds and become tinged with purple as the flowers near the end.
The fruit is a spindle-shaped follicle 15 cm long, which splits open when ripe and releases seeds with long tufts of hair.

[Cultivation]
Propagate from seed or by cuttings.
The optimum germination temperature is rather high, 20–25°C, so raise seedlings indoors; it has a taproot and dislikes transplanting, so sow in pots and then plant out.
It also spreads well by self-sown seed.
For cuttings, immediately rinse the cut end with water or soak it in water to wash off the milky white latex, then let the cut end dry before inserting it.
It can overwinter outdoors in the Kanto region and areas to the west, where heavy frost does not fall.
It prefers sunny, fertile soil with good drainage, water retention and aeration.
Poor drainage causes root rot.
For potted plants, water thoroughly when the soil surface dries; for plants in the ground, rainfall is sufficient.
Take care not to let it become too wet, and since the flowers and leaves are easily damaged by rain, move potted plants out of the rain during long rainy spells.
Apply slow-release chemical fertilizer as base fertilizer, and also give liquid fertilizer about once a month during the flowering period.
There are no particular pests or diseases.

[Notes]
The name Blue Star seems to be a popular name given in Japan because of its star-shaped blue flowers, and does not seem to be an English name.

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