Polygala vulgaris Seeds | Common Milkwort
LATIN NAME: Polygala vulgaris
COMMON NAME: Common Milkwort
Plant Profile
Every field guide shows the milkwort as a small flower shaped like a pea, and every field guide is describing a resemblance rather than a relationship. The flower has its own architecture. Two broad lateral petals stand out on either side, and between them lies a keel made of three fused petals, topped with a fringed crest that gives the flower its odd, broken outline. Eight stamens are joined into a tube that wraps the style, and the anthers open inside it, so the pollen is delivered as a package rather than as dust. The plant makes no nitrogen-fixing nodules, unlike the legumes it stands next to in the order Fabales, and the seed sits in a small flattened capsule rather than a pod.
Polygala vulgaris is a low plant, usually between ten and thirty centimetres, with a woody base, a slender taproot and stems that stay semi-evergreen through a mild winter. It grows in ground that is dry, thin and left unimproved, and its presence is a signal that a meadow has never been ploughed and manured.
The keel is the working part of the flower. It encloses the stamens and style in a tube, and the fringed crest at its tip lets a visiting bee press the flower open and release pollen onto its body. Small bees and hoverflies are the usual visitors, working the short greenish heads in late spring and early summer. Because the flower is built around a single narrow opening, the pollinator has to land precisely, and the style carries a brush of hairs that sweeps pollen from the visitor as it withdraws.
Flower colour runs from blue and purple through pink to white, and neighbouring plants in the same patch often differ. The colour is not a reliable guide to species, and identification depends on the wing sepals, the leafy bracts on the flowering stem and the shape of the leaves, which are narrow on the upper stem and broader near the base. The plant shows this range of colour within one meadow, which is why older county floras list several colour varieties that nobody now treats as distinct.
Science & Biotechnology
Polygala is one of the larger genera of flowering plants, with several hundred species, and the group is notoriously difficult to split into sections on appearance alone. Its leaf chemistry has helped. The genus builds flavone C-glycosides such as vitexin and isovitexin, where the sugar is joined to the flavone skeleton by a bond that survives acid treatment, and the pattern of those compounds, together with the xanthones found in some species, has been used to test which species really belong together. The same pigments make milkwort leaves easy to screen once a sample has been dried.
Uses & Benefits
The root of the genus carries triterpene saponins of the senegin type, named after the North American seneca snakeroot, whose bitter root was once the commercial standard; the aglycone behind them, presenegenin, is the skeleton the sugars are attached to, and the North American species also yields methyl salicylate, the wintergreen-scented ester. European milkwort is far milder in this respect than its American relative, but the root was still gathered for the herb trade, and the doctrine of signatures gave the plant its name and its reputation as a herb that increased the milk of nursing mothers and cattle. Later chemistry has given that reputation a limited basis: saponins are surface-active and irritant as well as bitter, and the modern trade prefers the stronger species.
The milkwort of European chalk grassland is Polygala vulgaris, and it is a different plant from the species that fill the medicine cabinets of East Asia. Two of those, Polygala tenuifolia and Polygala japonica, supply a standard expectorant and calming root in Chinese practice, and the North American Polygala senega supplied the seneca snakeroot of the old Atlantic trade. The family resemblance in chemistry is real, since all of them build triterpene saponins, but the European species was never a major article of commerce and the dried root traded under those names does not come from it. Growers should keep the distinction in mind: European milkwort is a wildflower of thin grass, not a crop with a pharmacopoeia behind it.
Growing from Seed
Use two parts coarse grit, two parts loamy subsoil and one part leaf-mould, and add no compost and no fertiliser, because rich ground grows grass that swamps the plant. Scatter the seed on the firmed surface and cover it with no more than two millimetres of grit, since light helps it start; press the surface gently and keep it damp with a fine mist. Space plants about fifteen centimetres apart, and expect the best results where the surrounding grass is kept short.
Milkwort needs open, short turf to persist, so mow or graze after the seed has set and take the cuttings away. The taproot runs straight down, which makes transplanting a gamble: move a seedling in a deep plug when it has two true leaves, or sow it where it is to flower and leave it alone. Slugs graze the young shoots and rabbits take the flower spikes, and competition from tall grass is the real reason plants vanish from a garden. Deadhead lightly to prolong the display, but leave the last flowers to ripen their capsules if you want the colony to spread.
Our Take
Treat this as a wildflower rather than a border plant: thin soil, short grass, no feeding, and it will seed itself into the gaps around its feet. The dwarf milkwort of the pine barrens is worth trying beside it in a sandy bed, as described in Polygala nana, and the pale-flowered annual of the same genus makes a good comparison in Polygala amarella. Anyone interested in the medicinal side of the genus, rather than the wildflower side, should look at Polygala tenuifolia, which is one of the species that actually carries that trade. Sow any of them in poor ground and let the grass stay short.
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