Polygala amarella Seeds | Dwarf Milkwort
LATIN NAME: Polygala amarella
COMMON NAME: Dwarf Milkwort
Plant Profile
Polygala amarella is a small perennial of short, grazed turf, with wiry stems rising from a woody base and narrow leaves crowding the lower part of the shoot. The spike is a loose raceme of blue, pink or occasionally white flowers, and each one is built on the milkwort plan: five sepals, of which the two inner ones are large and petal-like, and only three true petals, joined at the base into a short tube. The lowest of the three is the keel, and its upper edge is divided into those fine lobes.
The rest of the flower is equally compact. The stamens are fused into a sheath around the style, the pollen is held in the hollow of the keel, and the style ends in a spoon-shaped stigma. Small bees and bumblebees work the spikes for nectar, and the fringed crest is the platform they grip when they land.
Grazing or a late cut is what keeps the plant visible and alive. Aim to hold the turf at about five centimetres through the growing season, and take any cut after the seed has shed, so that the elaiosome-bearing seed reaches the ground. Never feed the ground, and never let grass litter lie over the rosettes in winter.
Science & Biotechnology
The genus is known for triterpenoid saponins, the polygalasaponins, built on aglycones such as senegenin, and the roots of the larger milkworts have a long history as expectorants in European and North American practice. Xanthones, among them mangiferin, also recur across the family, and Polygalaceae is unusual among the legumes and their allies in producing them in quantity.
Dwarf milkwort is not one uniform genetic entity. Counts of 2n = 34 and 2n = 68 have both been reported in European material, so the species contains at least a diploid and a tetraploid race, and the two do not always share the same ground or the same flowering period. Telling them apart in the field is not possible; a chromosome count or a flow-cytometry reading is needed.
Sequence data removed one of the old certainties about the genus. Polygala in its broad, traditional sense turned out to be polyphyletic, and the sections that botanists had once described on flower shape have been reinstated as separate genera. The small European milkworts remain in the narrowed genus, close to common milkwort.
Uses & Benefits
The English name records a belief rather than a fact. Milkworts were held to increase the milk of cattle and of nursing mothers, and the genus name says the same thing in Greek: poly, much, and gala, milk. No such effect has been documented, and the idea belongs with the other signatures that the old herbals accumulated.
The plant wants what old pasture offers: thin rendzina over chalk or limestone, a sward kept short by grazing, and full sun. Ploughing of ancient grassland, phosphatic fertiliser, airborne nitrogen and the abandonment of grazing have all worked against it, and dwarf milkwort now survives chiefly in small populations on the remaining unimproved sites of lowland Europe.
The seed carries a small fleshy appendage, an elaiosome, rich in the lipids and proteins that ants want. A foraging ant carries the seed to its nest, eats the appendage and leaves the hard seed underground, often in better-aerated soil than the surface the parent grew on. The partnership is the plant’s main route of spread, which is why a colony can creep across a downland slope but rarely crosses a ploughed field.
Growing from Seed
In a garden the plant is happiest in a limestone trough or at the front of a raised bed, where drainage is sharp and the competition thin. Seed is also used in chalk-grassland restoration, sown onto prepared, nutrient-poor ground after turf stripping.
Sow on the surface of a mix of three parts sieved limestone grit, one part leaf mould and one part coarse sand, and press the seed in with a board rather than covering it, because the seed is small and needs light. Keep the pan in full sun and only just damp. Pot the seedlings on when they show two or three true leaves, and plant out when the rosettes are 3 to 5 cm across, at 10 to 15 cm apart.
Our Take
Anyone raising dwarf milkwort should start with the ground rather than the seed, because a rich soil will smother it in a season. If you like the look of the genus, common milkwort is the easier plant and takes a slightly taller sward, while the North American candyroot wants the same sharp drainage on the other side of the Atlantic. The Chinese thin-leaved milkwort is grown for its roots rather than its flowers.
Related Reading
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