Common Name: Sweet Coltsfoot

General Information

Petasites japonicus is a vigorous, spreading, herbaceous perennial plant with a rhizomatous rootstock. A clump of large leaves 40cm or more across on petioles up to 60cm high are produced from the rhizomes. The plant sends up flowering stems in late winter before any leaves are produced, the leaves appearing in early spring[].
The plant is harvested from the wild for local use as a food and medicine. It is sometimes cultivated as a food crop in eastern Asia and the leaf petioles are often sold in local food markets[, ]. The plant is sometimes cultivated as an ornamental, valued especially for its flowering in late winter, and it can be used as a groundcover.
A very invasive plant, its roots are very difficult to eradicate[]. The plant has often escaped from cultivation and has become naturalized in many areas.

Known Hazards

None known

Botanical References

, ,

Range

E. Asia - Russian Far East, China, Japan, Korea. Naturalized in parts of Europe.

Habitat

Moist woods and thickets[]. Sreamsides, grassland and thickets in China[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	0.60 m
Growth Rate	Fast
Pollinators	Insects
Self-fertile	No
Cultivation Status	Cultivated, Wild

Cultivation Details

Succeeds in ordinary garden soil[], but prefers a deep fertile humus-rich soil that is permanently moist but not stagnant, succeeding in shade, semi-shade or full sun[]. Requires a moist shady position[]. Plants can be grown in quite coarse grass, which can be cut annually in the autumn[].
A very invasive plant, too rampant for anything other than the wild garden[, ]. Its roots are very difficult to eradicate[].
Sometimes cultivated in E. Asia as a food plant[, ]. The sub-species P. japonicus giganteus has huge leaves up to 1.5 metres across on stems 2 metres tall[]. It has a poorer flavour than the species type[].
Dioecious, male and female plants must be grown if seed is required.

Edible Uses

Leaf stalks - cooked and used like rhubarb[, , , , ]. The stems can be up to 1.2 metres long[]. They can be boiled and seasoned, pickled and used in winter soups or preserved in miso[]. They can be boiled, dipped in cold water then peeled and baked - they have a pleasant fragrant taste[].

Young flower buds cooked or used as a flavouring[, , , , ]. Delicious[]. A slightly bitter yet agreeable flavour[, ], they are much prized in Japan[]. They can be eaten whilst still green with miso or boiled down in soy sauce[].

The young flowering stems can be eaten cooked[].

Medicinal

The plant (though the exact part of the plant used is not specified) is antiasthmatic, antispasmodic, expectorant and poultice[]. A decoction is used in the treatment of chronic coughing and pulmonary 'deficiency', laboured or difficult breathing and asthma, constant sputum formation and pulmonary tuberculosis[].

The rhizomes are used medicinally for treating injuries, trauma, swelling, and fractures, and detoxification of snakebites[].

Agroforestry Uses:

Plants can be grown as ground cover in damp shady places[]. They are too invasive for most gardens and should only be used where they have plenty of room[].

Other Uses

The leaves of the sub-species P. japonicus giganteus are used as umbrellas by Japanese children[]. The leaf stalks can be used as walking sticks[].

Propagation

Seed - we have no information on this species but suggest sowing the seed in a cold frame as soon as it is ripe or in early spring. Only just cover the seed and do not allow the compost to dry out. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer.
Division succeeds at almost any time of the year. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.