- Written also: Small Meadow Rue
- Family: Buttercup Family – Ranunculaceae
- Growing form: Perennial herb.
- Height: 40–80 cm (16–32 in.). Stem unbranched until inflorescence, bristly.
- Flower: Regular (actinomorphic), purple–lime greenish, approx. 1 cm (0.4 in.) across. No petals. Sepals 4–5, purplish–light green, withering early. Stamens many, filaments approx. 3 mm (0.12 in.) long, purple, anthers slightly shorter than filaments, nodding, usually terminated by a short bristle. Gynoecium separate, several pistils. Inflorescence lax, usually with an abundance of flowers, often with a very leafy raceme, flowers spreading–erect.
- Leaves: Alternate, stalked, stipulate. Leaves 6–8. Blade quite elliptic, longer than broad, 2–3 times pinnate. Leaflets usually exstipulate. Leaflets narrowly obovate–ovate(–almost round), 3-lobed.
- Fruit: 8-ridged, sharp-pointed, 2–3.5 mm (0.08–0.14 in.) long, stalkless achene.
- Habitat: Forest margins, broad-leaved forests, coppices, shore bank, flood-influenced meadows, meadows, roadside embankments.
- Flowering time: June–July.
- Endangerment: Ssp. simplex is an endangered species in Finland.
Close to 100 meadow-rue species have been classified, 13 of which grow in Europe and 6 in Finland. Although the number of species is very modest, it is not so easy to differentiate between them. Small meadow-rue’s scientific species name simplex, ’simple’, refers to its simply branchless or at most short-branched stem from the inflorescence – but if the name-givers had been aware of how complicated the species and its close relatives are, it would probably have been named complex! Small meadow-rue’s subspecies simplex and boreale are reasonably widespread in Finland. They can be most easily confused with another of our more common meadow-rue species, yellow meadow-rue (T. flavum; also known as common meadow-rue), although its inflorescence is usually dense and the filaments of its stamens are light-coloured.
The tepals in most Buttercup family flowers are large and colourful; on meadow-rues they fall away early, and they don’t secrete any nectar to tempt pollinators. The tepals’ job of attracting the interest of insects is partly taken on by the colourful and fragrant stamens, which reward flies and beetles that help with pollination with an abundance of pollen. A transition can however be observed in the meadow-rue family from insect pollination to wind pollination in in-between forms. Wind pollination is usually regarded as a more primitive feature than insect pollination: the advantage of animal pollination is its precision because the pollen is transported mainly to other flowers of the same species. Meadow-rues are as good example of an evolutionary development series in which the flower’s method of pollination varies between insect pollination and previously-developed wind pollination. Evolution would appear to be moving backwards, but that is an illusion created by our way of thinking: natural selection favours any solution that gives the species the best chance of survival.