Inula japonica Seeds | Japanese Inula

Categories：Herb

Japanese Inula (Inula japonica) seed — Japanese Inula (*Inula japonica*): Asteraceae — Inula, native to Damp ground, stream banks and wet meadow edges from eastern China and Korea through Japan; the same or a closely allied plant is recorded across temperate Asia.

LATIN NAME: Inula japonica

COMMON NAME: Japanese Inula

Plant Profile

Look closely at one of the golden heads and you are looking at two different flowers doing two different jobs. The outer ring is made of ligulate florets, each a single strap-shaped petal with its own tiny tube at the base. The centre is packed with tubular florets, narrow and five-lobed, and it is these that set most of the seed. Several rows of overlapping bracts hold the whole structure together, and the heads sit in a loose, flat-topped corymb that opens from the outside inward. The achenes that follow carry a pappus of bristles, which is how the seed leaves the riverbank in the wind.

The plant was described by Thunberg from Japanese material, and the boundary between it and Inula britannica has shifted ever since. Some treatments keep them as two species separated by leaf shape, flower size and the persistence of the hairs on the stem and the bracts; others sink the Japanese plant into Inula britannica as a variety. The confusion is practical as well as academic, because dried heads sold in trade may be either. Related species in the same genus, such as Inula salicina and Inula conyza, are narrower-leaved and prefer drier ground.

Stems are hollow and get top-heavy in flower. Group the plants so they lean on one another, or run a single strand of twine around the clump at about a third of its height. Water during flowering if the ground dries, and cut the stems to the base after the seed begins to shed if you do not want seedlings across the bed.

Science & Biotechnology

The aerial parts are rich in sesquiterpene lactones, the bitter compounds that give the family its chemistry. Britannin is the best known of them, and 1-O-acetylbritannilactone and its relatives belong to the same series. These molecules carry an alpha-methylene gamma-lactone group that reacts readily with thiol groups on proteins, which is the basis both of their biological activity and of the allergic and irritant reactions that sesquiterpene lactones can provoke in sensitive people. Flavonoids including quercetin and luteolin accompany them, and together the fractions are why the plant appears so often in studies of anti-inflammatory and insect-feeding work.

Extracts and isolated lactones from the genus have been examined for anti-inflammatory activity and for their effect on insect feeding, where the same reactive lactone group makes the tissue unpalatable to many generalist herbivores. Aqueous extracts of the dried heads are also used in infusions, where the bitterness is part of the point.

Uses & Benefits

The roots and rhizome of this genus store carbohydrate as inulin, a fructan built from chains of fructose with a glucose unit at the end. Inulin is not digested in the human small intestine, so it behaves as a soluble fibre, and the same property makes Inula roots a source of fructan for the food trade. The closely related elecampane is the commercial example, but the storage pattern runs through the genus, and the sweetish, slightly earthy taste of a root decoction comes largely from that fructan fraction rather than from sugar.

This is a plant of damp, disturbed ground: river levees, roadside ditches, the wet edge of fields. It was gathered for medicine long before it was grown, and the dried flower heads and the aerial parts both have a place in the older pharmacopoeias of eastern Asia. It is also a useful pollinator plant, because the flat heads are easy landing platforms for bees, hoverflies and small beetles, and the flowering period is long.

Growing from Seed

Give it the wettest sunny spot available, or water it steadily through the first season. The plant resents drying out at the root but will not sit in stagnant water, so a soil that holds moisture yet drains is ideal. Set plants out when they have several pairs of true leaves and keep the ground between them clear until the crowns close over.

Divide every few years after flowering, when the centre of the clump begins to die out. Lift the whole root mass, cut it into sections each with several strong buds, and replant at the original depth. A light mulch of compost in autumn is all the feeding it needs, and old stems left standing through winter shelter overwintering insects.

Our Take

Sow it where the ground stays damp and the sun reaches it, and the flat golden heads will do the rest. Among its close relatives, elecampane is the tall Inula grown for its inulin-rich root, while British inula is the species most often confused with this one in the trade. Willow-leaved inula suits a drier border, and ploughman’s spikenard is the biennial relative of rough grassland and scrub.

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