Matted St. John's Wort
Hypericum japonicum

Family: Hypericaceae

What it is like

Hypericum japonicum is a ANNUAL/PERENNIAL growing to 0.5 m (1ft 8in). It is in flower from July to August, and the seeds ripen from August to September. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil.

Height (m): 0.5

Where it is found

Wet places in lowland, C. and S. Japan. Rice fields, ditches, marshes, grasslands and waste places from sea level to around 3000 metres.

E. Asia - China, Japan to Australia and New Zealand.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 0

Medicine

Rating: 2

The plant is alterative, antiphlogistic, astringent, depurative, febrifuge and vulnerary. It is decocted with water for use. It is used in the treatment of asthma and dysentery, acute hepatitis, pain in the liver region, appendicitis, boils and abscesses and has also been used as a styptic. The plant has also shown antitumour activity.

Antiphlogistic: Reduces inflammation.

Depurative: Eliminates toxins and purifies the system, especially the blood.

Dysentery: Used in treating dysentery - an infection of the intestines that causes diarrhoea containing blood or mucus.

Febrifuge: Reduces fevers.

Vulnerary: Promotes the healing of wounds.

Other

Rating:

How it is grown

Easily grown in any reasonably good well-drained but moisture retentive soil. Succeeds in sun or semi-shade but flowers better in a sunny position. This species is found in the wild in wet soils. A very variable species.

Propagating it: Seed - sow spring in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in late spring. It might also be worthwhile trying an outdoor sowing in April.

Best place to grow: Bog Garden;

Habit: Annual/Perennial

Hardiness:

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist, wet

Things to keep in mind

The plant is suspected of causing photo-sensitization. Feeding trials to livestock in New Zealand have shown that it is non-toxic.

Its other names

Local names

Synonyms

H. calycatum. H. pusillum.