- Type
- Trees & Vines
- Difficulty
- Hard
- Season
- Spring·Summer
- Sowing
- Plant a sapling
Eucommia
Eucommia ulmoides
Gutta-percha threads and chlorogenic acid · a tree whose bark is steeped as tea
Eucommia is a deciduous tree, and what goes into the teapot is its bark and its leaves. Snap a piece of bark and white threads stretch across the break and hold; those threads are gutta-percha, a rubber, and they are how eucommia is recognised. The family Eucommiaceae contains this one species alone, which leaves it standing by itself in plant classification. Reported constituents of bark and leaf include chlorogenic acid, aucubin and geniposidic acid, and since this is not the tea plant there is no caffeine in it. The Donguibogam lists it in the Wood section as 杜仲, giving it a nature both neutral and warm, a pungent and sweet taste, and no toxicity. Its form resembles that of hubak (厚朴), the entry says, and the pieces reckoned best are those that show white threads running unbroken across a snap; it also records the preparation — pare off the outer bark and cut across the grain so the threads part. Sasseonmok (思仙木) and seoksaseon (石思仙) are given as other names. The tree is planted in Korea too, but bark takes years to be worth taking, and stripping a living trunk right around kills it.
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Where It Grows
- Origin Native to the mountains of Sichuan, Guizhou, Hunan and Shaanxi, which supply almost all of the Eucommia bark traded worldwide. Wild trees are very rare, and most of what is produced today comes from cultivated stock.
- Major producer Since the 1970s it has been planted in North Chungcheong, North Gyeongsang, South Jeolla and elsewhere, and harvested for its leaves and bark. The scale is nowhere near China's.
- Major producer It is grown in plantation fields in Nagano, Kyushu and elsewhere, with the leaves destined for tea.
The tree was native only to the mountains of central China, and it is the sole surviving species in the family Eucommiaceae. In Korea and Japan it was introduced as a planted tree, so it does not occur in the wild. Even in China the wild populations have all but vanished, and everything on the market comes from cultivated trees.
- Optimum
- 15~25℃
- Range
- 5~30℃
- Hardiness
- Hardy
A deciduous tall tree of warm-temperate mountain country. It withstands winters of around -20℃, so it grows well from central Korea southward, and it dislikes spots where water pools. The bark peels cleanly only while the cambium is active, from late spring to early summer — just a few weeks a year.
Harvested 2–15 years after planting. Seedlings planted in spring yield pickable leaves within a couple of years, but for bark you wait more than ten years until the trunk has thickened. Leaves are harvested in summer, bark between late spring and early summer.
In Korea Central Korea and south
Hardy enough to overwinter (survive the winter outdoors) even in central Korea, though it grows best from the central region southward. It is planted in North Chungcheong, North Gyeongsang and South Jeolla.
How to grow
- Light
- A spot with five or six hours of sun. It grows into a large tree, so plan for the shade it will cast later
- Soil and depth
- Deep, rich, free-draining ground. Avoid anywhere water sits
- Spacing
- Four to five metres between trees. Mature height passes ten metres, so keep it well clear of walls and buildings
- Watering
- Keep it from drying out through the first two years only. Once rooted it largely carries itself on rainfall
- Feeding
- Work compost around the base in late autumn after leaf fall. Heavy nitrogen only lengthens the branches and thins the bark
- Harvest
- Pick leaves in summer and roast them. Bark comes away cleanly only once the trunk has thickened and the cambium is active, between late spring and early summer. Never ring the trunk — take a narrow vertical strip from one side
What makes the difference. Pare the rough outer layer off stripped bark and dry it in the sun. Cut the dried bark across the grain and dry-roast it so the threads part and it simmers more easily. When buying, choose pieces that show dense unbroken threads at a snap
Why this one is harder. Bark is years away — the trunk has to thicken first. Leaves can be picked two or three years after planting, so one tree in the yard and leaf tea to begin with is the practical route. The tree is dioecious, so fruit needs more than one tree
Common problems
- Aphids You will see Colonies on new growth and leaf undersides in spring, leaves turning sticky What to do Wash off with a jet of water; if it recurs, use an egg-yolk oil spray. Do not spray at all where the leaves are for tea
- Root rot You will see Leaves yellow after a wet spell and branch tips die back What to do Avoid spots where water sits and raise the planting. Dig out a rotted tree and do not replant in the same place
This page describes how a crop is grown and used. It does not claim health effects for any food, nor is it intended to prevent or treat disease. Component and study notes are references only and do not mean the same result occurs in people. Consult a medical professional about health concerns.
Health Benefits
The old record — ducung (杜仲). The Donguibogam lists it in the Wood section as 杜仲. It records a nature both neutral and warm, a pungent and sweet taste, and no toxicity. Its form resembles that of hubak (厚朴), and the pieces reckoned best are those where white threads run unbroken across a snap. The preparation is set down as well: pare off the outer bark and cut across the grain so the threads part. Sasseonmok (思仙木) and seoksaseon (石思仙) are given as other names. What an old medical text wrote differs from how it is judged today.
What the white threads are. The threads the old record used to grade good bark are known today as gutta-percha, a rubber. Compositional analysis confirms that the tree produces it and lays it down in bark and leaf. This is a record of a material property.
Analyses of bark and leaf. Repeated analyses report the isolation of chlorogenic acid, aucubin and geniposidic acid from eucommia bark and leaf. The same work reports that bark and leaf differ in composition. This is an analysis of composition.
Nutrition
- Gutta-percha (stretches into threads when bark or leaf is snapped) — the rubber that identifies eucommia
- Chlorogenic acid (reported in bark and leaf) — a polyphenol distributed widely across plants
- Aucubin and geniposidic acid (isolated from leaf and bark) — iridoid glycosides
- No caffeine (this is not the tea plant) — roasting and steeping the leaf brings no caffeine with it
The white threads — gutta-percha Snap a piece of eucommia bark or leaf in two and white threads stretch across the break and hold. They are gutta-percha, a rubber the tree produces and stores. That is why bark showing dense threads that resist parting has always been graded the best. It is not a component that dissolves into the cup.
Chlorogenic acid and iridoids Chlorogenic acid, aucubin and geniposidic acid have been reported in the bark and the leaf. Bark and leaf do not share a composition, so what enters the cup depends on which one the tea was made from. This entry stays with the compositional record.
A tea without caffeine Eucommia tea is steeped from the bark or leaf of this tree rather than from tea leaves, so it carries no caffeine. That it can be drunk in the evening without disturbing sleep is how it settled into use as a late-hour drink. The taste is lightly toasty with a faint astringency behind it.
What the brewing method changes Bark is hard and gives up little to a short steep, so it is simmered for around twenty minutes. Leaves are roasted first, then steeped in hot water for about three minutes. A long-simmered bark tea looks stronger, but it draws out the astringency along with everything else.
Pairings
○ Jujube and ginger — Simmering the bark with jujube brings a sweetness that makes it easier to drink. Two or three slices of ginger at the end add aroma. A handful of bark to a litre and a half of water makes a comfortable day's worth. Ginger · Jujube
○ Dry-roasting first — Cut the bark and dry-roast it in a pan: the white threads part, it simmers more readily, and a toasted aroma comes up. The preparation the Donguibogam records was the same idea — cut across the grain so the threads break. Roast only until the colour deepens slightly, never to burning.
○ Roasting summer leaves — Pick leaves in summer, wash and drain them, then dry them slowly in a pan over low heat for a leaf tea. The leaf is the part that can be taken every year without touching the bark. Once fully dry, seal them in a container and keep them somewhere cool.
△ Never strip the bark right around a living tree — Take bark in a full ring around the trunk and you sever the path that carries water and nutrients; the tree dies. Take a narrow vertical strip from one side only and leave the rest of the circumference intact. Do not strip bark from trees in someone else's woodland or in a park.
△ Do not treat leaf tea and bark tea as the same thing — Eucommia leaf and bark do not share a composition. Commercial products are split between pure-leaf and bark-blended, so read the label for which one it is. Buying leaf tea while picturing bark tea, or the reverse, gives you a different drink from the start.
△ Do not drink it strong and long like a medicine — Studies on eucommia have mostly used extracts drawn from bark or leaf, a different quantity and form from a steeped tea. Anyone planning several strong cups a day over a long stretch should first check it against the medicines they are already on. If a blood-pressure prescription is involved, do not add it on your own judgement.
Varieties
- Bark (ducung) (part) — Stem bark stripped and dried. The pieces reckoned best show dense unbroken threads at a snap
- Leaf (part) — Summer leaves pan-roasted and steeped. Its composition is not the same as the bark's
- Roasted bark (processed) — Bark cut and dry-roasted so the threads part. It follows the old preparation exactly
Source: Dongui Bogam, Wood section (Mokbu), entry on Dujung (Eucommia)