- Family: Milkwort Family – Polygalaceae
- Growing form: Perennial herb. Rhizome branched.
- Height: 10–25 cm (4–10 in.). With many stems. Stem ascending–almost erect, usually unbranched, slightly woody base, hairy.
- Flower: Irregular (zygomorphic), 6–8 mm (0.24–0.32 in.) long. Corolla usually blue, occasionally bluish violet, rose-red or white, fused at base, tubular, 3-lobed; uppermost lobes round-tipped, lowest keel-like, many-lobed at tip. Sepals 5, internal 2 large, clearly longer than capsule, petaloid, net-veined; outer 3 bluish–green, short, narrow. Stamens 8, in 2 groups. Gynoecium composed of 2 fused carpels. Inflorescence quite long, a quite lax, 10–30-flowered terminal raceme, bracts fall away early.
- Leaves: Alternate. Blade lanceolate–elongated, hairy, with entire margin. Lower part of stem leafless in flowering time.
- Fruit: Cordate, flat, 2-parted capsule with widely membranous edges.
- Habitat: Meadows, pastures, banks, stony hummocks.
- Flowering time: June–July.
- Endangerment: Vulnerable, protected in the whole of Finland except the Åland Islands.
Common milkwort’s fetching blue flowers make it an attractive plant on dry meadows and fields. To those who are familiar with the plants, the flower might bring to mind those of the Pea family, even though they are in no way related to each other. Their modus operandi is however similar: only large and heavy insects – such as bees – are able to bend the lower petal’s grooved tip downwards to open the way to the nectar. The stamens and pistils are simultaneously exposed, and pollination may occur. Two of milkwort’s petals are quite small and its large, petaloid lateral lobes are actually sepals. Usually a flower’s sepals protect the bud while the petals attract potential pollinators, but milkwort’s do not subscribe to this strict division.
Common milkwort grows in the Åland Islands and it can also be found on the Turku archipelago, but stands on mainland Finland seem to have vanished. It also grows in Sortavala on the Russian side of the border but it has yet to be spotted in the meadows of eastern Finland. Its close relative dwarf milkwort (P. amarella), which has smaller flowers and a clear leaf rosette, still grows on mainland Finland.
On the Åland Islands common milkwort can be confused with tufted milkwort, which has long-lasting bracts and whose petaloid sepals are usually the same length as the capsule and clearly purple. Tufted milkwork is an endangered species and it is protected on the Åland Islands. Tufted milkwort is a calcicole (only grows on soils with lime).