- Type
- Trees & Vines
- Difficulty
- Easy
- Season
- Spring
- Sowing
- Plant a sapling
Castor Aralia
Kalopanax septemlobus
Saponins · spring shoots from a thorned tree
Castor aralia is a deciduous tree in the ginseng family (Araliaceae), its trunk and branches set with broad, heavy thorns. The leaves are palmate with five to nine lobes, and a mature tree passes 10m, so it belongs at the edge of a plot or in a corner of a yard rather than in a raised bed. Saplings go in during early spring, and it takes several years before the tree carries shoots worth picking. In Korea the spring shoots are sold as gaedureup, picked in April or May while still furled. They are not eaten raw. Blanch them 30 seconds to a minute in lightly salted boiling water, rinse in cold water, and throw the blanching water away. The Donguibogam has an entry for 海桐皮 in its Wood section, calling its nature neutral, or warm by another account, with a bitter taste and no toxicity, and saying the bark resembles the white bark of catalpa and grows in Korea only on Jeju. Korean practice has long treated castor aralia bark under the name haedongpi, but whether the 海桐皮 of the old record is the same tree as today's castor aralia is disputed. The tree itself now grows in mountains across the country and is raised on farms.
Year-Round Calendar
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Where It Grows
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Main producer
It grows wild in mountain areas nationwide, and Korea also has the largest scale of field cultivation grown for picking the spring shoots. Harvest April, May
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- Major producer It is found in the mountains of China's three northeastern provinces and of Shandong and Zhejiang, where the bark is harvested.
- Wild population Known there as harigiri, it is common in the mountains of Hokkaido and Honshu. It is handled mainly as timber.
- Wild population It is found in the broadleaf forests of Primorsky Krai and southern Sakhalin.
Its range is the temperate broadleaf forest of East Asia, stretching across the Korean Peninsula, northeastern China, Japan, and the Russian Far East. The practice of eating its spring shoots is most widespread in Korea, while Japan and Russia treat it as a timber tree — the same tree, harvested for different things.
- Optimum
- 15~25℃
- Range
- 0~30℃
- Hardiness
- Hardy
A tall deciduous tree of the northern temperate zone, it tolerates cold down to -30℃. It grows best where moisture lingers, as in valley bottoms; in deep shade it grows thin and leggy, and the shoots turn slender.
Harvested 3–5 years after planting. After a seedling is planted, three or four to five years must pass before it is large enough for its shoots to be picked. No shoots are taken in the year of planting, so the planting month and the harvest month do not fall in the same year.
In Korea Nationwide
The tree grows wild in mountain areas nationwide, with plantations for shoot harvesting in the mountain districts of Gangwon, North Gyeongsang, and North Jeolla.
How to grow
- Light
- Five hours of direct sun or more. It will grow in part shade, but the shoots come thin
- Soil and depth
- Free-draining, fertile ground at least 40cm deep. It favours sites that hold moisture, like the foot of a slope
- Spacing
- 4 to 5m apart if grown as a full tree; 1.5 to 2m if kept low for shoot picking
- Watering
- Only the first summer needs watching for drought. Once established it needs almost none
- Feeding
- Ring well-rotted compost under the drip line in late winter. Too much nitrogen pushes leggy growth and heavier thorns
- Harvest
- Pick in April or May while the shoot is furled at 5 to 10cm. Leave one terminal bud on each branch rather than taking them all. Strip every bud and no new growth follows that year, and the tree weakens
What makes the difference. For shoot picking, cut the trunk back to 1.5m in the second or third year and let side branches form. The shoots then come at arm's height and no ladder is needed
Why this one is harder. The thorns are the real difficulty. Young trees carry the thickest, densest ones, so thick gloves and long sleeves are not optional. Do not plant beside a path or anywhere children pass
Common problems
- Fall webworm You will see Leaves bound in webbing at the branch tips, eaten out from inside What to do Cut out the whole branch while the nest is small and bag it. Once it spreads through the tree, hand control stops working
- Aphids You will see Colonies on new shoots and leaf undersides, leaves turning sticky What to do Wash off with a jet of water; if it recurs, use an egg-yolk oil spray. On a tree you pick shoots from, stay with water and hands rather than chemicals
- Scale insects You will see White or brown shell-like bumps on the branches, with sooty black on the leaves below What to do Scrape them off with a stiff brush in winter; at high density use a dormant horticultural oil while the tree is leafless
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 Donguibogam entry for 海桐皮 — whether it is this tree is disputed. The Donguibogam carries an entry for 海桐皮 in its Wood section. It gives the nature as neutral, warm by another account, the taste bitter, and records no toxicity. It says the bark resembles the white bark of catalpa and may be stripped in any month, and adds that in Korea it is found only on Jeju. Whether the 海桐皮 of the old text is the same tree as today's castor aralia, however, is disputed. Korean practice has long treated castor aralia bark under the name haedongpi, but the two names cannot be declared identical. This is a historical medical record and differs from modern medical judgment.
Saponin analysis of the bark. Analyses report the isolation of triterpenoid saponins known as kalopanaxsaponins from castor aralia bark. The same work reports wide variation in content with plant part and harvest date. This concerns chemical composition, and nothing has been confirmed in modern terms about what happens when a person eats it.
Nutrition
- Triterpenoid saponins (kalopanaxsaponins reported isolated from the bark) — glycosides behind the bitterness and foaming
- Polyphenols (detected in shoots and leaves) — involved in astringency and the browning of cut surfaces
- Dietary fibre (rises as the shoot opens out) — cell wall polysaccharides
Water and fibre in the spring shoot A gaedureup shoot is mostly water, and its bite comes from cell wall fibre. The further the shoot opens, the coarser that fibre gets, and blanching will not soften it back. Pick at 5 to 10cm while the shoot is still furled. A day after picking the base is noticeably tougher, so blanch the same day.
Bitterness and saponins The bitter edge of the shoot is reported to relate to saponin-class compounds. The shoots are not eaten raw. Blanch them 30 seconds to a minute in lightly salted boiling water, then rinse in cold water and squeeze out the moisture. Much of the bitterness leaves with the blanching water, which is thrown out rather than kept for broth. To hold on to some of that bitterness, do not cut the blanching short. Adjust it in the dressing instead: doenjang leaves the bitterness standing, chogochujang covers it.
Minerals and blanching losses Spring mountain greens are reported to carry a respectable share of minerals such as potassium and calcium. Water-soluble compounds do leach out during blanching. The blanching water is thrown away for the harsh taste, and the loss is simply accepted. Actual figures vary widely with picking date and plant part.
Pairings
○ Blanched, with chogochujang or doenjang — This is the everyday use. Blanch in salted boiling water, rinse cold and squeeze out the water. Chogochujang covers the bitterness while doenjang leaves it standing.
○ Fritters and pancakes — A thin batter on blanched shoots softens the bitterness in the oil. It is the easiest way to serve them to someone eating gaedureup for the first time. A thick batter buries the shape of the shoot entirely.
○ A piece of bark in chicken broth — Adding one piece of bark to a long-simmered chicken pot is an old cooking habit. It leaves a faint aroma and a bitter edge in the broth. That culinary amount is the whole of it; piling in bark to make the broth stronger only turns it muddy.
△ Raw shoots - never eaten uncooked — Gaedureup shoots are not eaten raw. Blanch them 30 seconds to a minute in lightly salted boiling water, longer for thick shoots, then rinse in cold water and squeeze out the moisture. Do not cut the blanching short in order to keep more of the bitterness; adjust that in the dressing, with doenjang or chogochujang. Throw the blanching water away rather than keeping it for broth.
△ Bark decoction - not something to drink daily — Steeping the bark has a long folk history, but nothing has been confirmed in modern terms about what happens when a person consumes it, and the saponin content of the bark is reported to vary widely with plant part and harvest date. A piece or two simmered in a chicken soup is one thing; a strong decoction drunk every day is not advisable, and least of all for anyone on medication or pregnant.
Varieties
- Wild type (sapling) — The mountain form. Dense, heavy thorns along trunk and branches
- Low-thorn selection (sapling) — Propagated from individuals with sparse thorns. Far easier to pick from
- Grafted stock (grafted sapling) — More even growth than seedlings. Cut low and managed for shoot picking
Source: Donguibogam, Wood Section 海桐皮 · Rural Development Administration (Nongsaro) · Korea National Arboretum plant list