Pueraria lobata Seeds | Kudzu

Kudzu (Pueraria lobata) seed — Kudzu (*Pueraria lobata*): Fabaceae, tribe Phaseoleae — Pueraria, native to East Asia — China, Korea and Japan; naturalised and invasive across the southeastern United States, South Africa and parts of the Pacific.

LATIN NAME: Pueraria lobata

COMMON NAME: Kudzu

Plant Profile

For most of the twentieth century the plant answered to Pueraria lobata, and the older Japanese name P. thunbergiana still appears in horticultural writing. Revisions of the genus reduced the species to a variety of the wider-ranging P. montana, an arrangement that reflects how freely the Asian and Pacific populations intergrade.

Each patch rests on a single woody root crown, sometimes as thick as an arm, from which vines radiate in every direction. Digging it out is the only permanent control, because the crown and its stored starch will rebuild the canopy after mowing, grazing or fire. A single stem can put more than ten metres of growth on a fence line in one warm season.

As a legume, kudzu carries root nodules full of nitrogen-fixing bacteria and feeds the ammonium it makes into surrounding soil. That changes the terms of competition for everything under the canopy, favouring nitrophilous weeds and often altering the nutrient status of a woodlot long after the vines are cut. The soil change outlasts the vine itself.

The popular nickname is not much of an exaggeration in the deep South. Dense mats of leaves and stems bury hedgerows, power poles, abandoned houses and the understorey of secondary forest, and the weight of the growth can pull down branches. Land managers now treat heavy infestations as a multi-year project rather than a seasonal chore.

Livestock will eat kudzu, and repeated, hard grazing by goats in particular can exhaust a patch over several seasons without chemicals. The method works best where the animals can be concentrated on a defined area and moved on before they ring-bark the trees you want to keep. It is slow, but it leaves the ground intact.

Science & Biotechnology

The root is a dense store of isoflavones, with puerarin, daidzein and daidzin the best known. Puerarin is unusual in being a carbon-linked glucoside, which makes it more resistant to breakdown than the sugar-linked isoflavones of soy. The root is sliced and dried for decoctions, and the starch left after the flavonoids are washed out becomes a food ingredient.

A small Asian plataspid, known as the kudzu bug, was found in the southeastern United States in 2009 and spread quickly through the vine’s range. It feeds on kudzu stems and also on soybeans, so it is both a natural check on the weed and a new agricultural pest. Researchers still debate how much it reduces kudzu vigour.

Uses & Benefits

Where the plant is valued, the root is processed for its starch. Washed, settled and dried, kudzu starch is sold in pale, crumbly blocks, dusted onto foods as a thickener and used to make translucent noodles and chilled confections. Its texture is distinctive: smooth when set, with a slight resistance that other starches do not reproduce.

Before it was a pest, kudzu was a fibre crop. Vines were retted, split and woven into cloth in Japan, where the fabric is known as shifu, and into paper and cordage in parts of China. The fibre is long and strong, and a small craft industry still produces shifu from wild-harvested vines in a few districts.

Growing from Seed

American farmers planted kudzu through the Depression years on the advice of soil conservation programmes, which paid for seedlings to stabilise gullies and exhausted cotton ground. The vine did that job very well. It also kept growing, and the states that sponsored it spent the following decades trying to reverse the decision, adding it to noxious weed lists in the late 1990s.

Treat the seed as you would treat a weed seed, because in much of the temperate world that is what it is. If you are planting it deliberately, choose a site with a hard physical boundary and no natural watercourse leading away. Scarify the seed coat, sow a few millimetres deep in late spring, and space plants at least two metres apart along the line you want covered.

Our Take

In the eastern United States, think very hard before you sow this one, and never plant it near a boundary you do not control. Where it is legal and contained, it is a useful forage and cover crop. Graziers often run it with red clover and milk vetch for a legume-dominant sward, while growers interested in the medicinal root trade compare it with liquorice. Botanists following the species’ spread will find its close relative catalogued as Pueraria montana.

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