Paeonia japonica ("Yamashakuyaku")

Japanese name: ヤマシャクヤク （山芍薬）
Scientific name: Paeonia japonica

[Overview]
A perennial 30–50 cm tall, found in deciduous forests.
It has a thick rhizome up to 1 cm across.
The leaves are alternate and biternate, 15–35 cm long including the petiole.
The terminal leaflet is narrowly obovate to elliptic, 6–14 cm long and 2–9 cm wide, with an entire margin.
The petiole of the leaves on the middle of the stem is 5–16 cm long.
The middle of the stem bears 2–3 leaves, and the leaves on the upper part of the stem are simple or divided into 3 lobes to the base, with petioles 1.5–3 cm long.
The underside of the leaf is usually hairless, or sometimes sparsely covered with appressed hairs.
A single large flower is borne at the tip of the branch.
The flower is white with 6 petals, 6–10 cm across, and opens halfway facing upward.
There are 2–3 pistils, and the stigmas are tinged with reddish purple and usually gently curved.
The sepals bend back at the fruiting stage.
The fruit is an obovate follicle 2.5–4 cm long, which splits open when ripe and exposes the seeds.
Fertile seeds are spherical and black, while infertile ones are red.

[Uses]
The root is used medicinally.

[Cultivation]
Propagate from seed or by division.
Divide the plant with buds attached to the rhizome.
From seed, germination takes 2–3 years, and flowering takes several years after germination.
It prefers partial shade and soil that is well drained, moisture-retentive and well aerated.
Grow it in a well-ventilated place where it is protected from strong sun and dryness throughout the year.
When planted in the ground, under deciduous trees is suitable.
It dislikes both dryness and excessive moisture.
Water thoroughly when the soil surface dries.
A lack of fertilizer reduces flowering, so in addition to base fertilizer, apply slow-release fertilizer in early spring, after flowering, and in autumn.
If you do not intend to collect seed, cut the flower stalk off at the neck after flowering so the plant does not become exhausted.
Pests and diseases include virus diseases, powdery mildew, teppomushi (longhorn beetle larvae), shoot borers and cutworms.

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