- Written also: Herb-Robert
- Family: Geranium Family – Geraniaceae
- Growing form: Annual or often biennial herb. Taproot many-branched.
- Height: 15–40 cm (6–16 in.). Stem many-branched, with spreading hairs, usually red.
- Flower: Regular (actinomorphic), 15–20 mm (0.6–0.8 in.) broad. Petals 5, dark rose-red, with paler veins, round-tipped. Sepals 5, with broadly membranous margins, glossy, long-haired, sharp-pointed, erect, around half shorter than petals. Stamens 10. Pistil of 5 used carpels. Flowers usually axillary in pairs or terminating stems.
- Leaves: In basal rosette and on stem opposite. Rosette leaves long-stalked, stem leaves stalked–almost stalkless, stipulate. Blade triangular, with palmate venation, with 3 leaflets (basal leaves sometimes with 5 leaflets), central leaflet long-stalked, leaflets pinnate–deeply lobed; lobes narrow, sharp-tipped.
- Fruit: 5-parted schizocarp, tip beak-like, coiling up when ripe. Mericarps with net-like surface, sparsely haired.
- Habitat: Mossy boulders in lush woods, rocky places, walls, rocky outcrops, hedgerows, seashores.
- Flowering time: June–September(–October).
If herb Robert is touched, its fragrance gives it away as a geranium (Pelargonium), a familiar group of house plants from South Africa. They emit a fragrance, especially upon being touched, which is intended to put potential predatory plant-eaters off their food. At least a certain percentage of people find the smell unpleasant. The smelly liquid that is acquired by boiling the plant is used in Finland to get rid of bugs and also to treat wounds. Its flowers are a deep rose-red and in light places the whole plant is often crimson, which is the same colour that it is in the autumn. Herb Robert grows relatively rarely in open places; it is more likely to be found in shady broad-leaved forests on rocky places and in crevices, where at least a small, spongy, nitrogenous build-up of leaves has occurred.
Many cranesbills spread by flinging their seeds out with the help of the flexible outer wall of the tips of their carpels. Herb Robert on the other hand relies on two white bristles that are deeply lobed at the tip and which reveal themselves only when the tip breaks away from the fruit. These fibres easily attach to passing people and animals, and can thus travel long distances. The species can also be met as a casual alien outside its clearly established habitat. If they can’t find a suitable ride the seeds attach to the plant’s own leaves and stem until the rotten carpel’s wall breaks and the seed falls to the plant’s roots.