- Name also: Garlic Root, Garlicwort, Hedge Garlic, Jack-by-the-hedge, Poorman’s Mustard
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Biennial herb. Taproot white, bent.
- Height: 30–100 cm (12–40 in.). Stem usually unbranched. With slight onion-like fragrance.
- Flower: Corolla regular (actinomorphic), white, approx. 1 cm wide; petals 4, approx. 5 mm (0.2 in.) long. Sepals 4, falling early. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme, extending in fruiting stage.
- Leaves: In basal rosette and alternate on stem. Rosette leaves long-stalked, upper stem leaves short-stalked. Rosette leaf-blades kidney-shaped, with rounded teeth (crenate), thin, underside hairy, upper side shiny, stem leaf-blades triangular–cordate, with serrated margin.
- Fruit: Many-seeded, bluntly 4-edged, 3–6 cm (1.2–2.4 in.) long, spreading siliqua. Stalk approx. 5 mm (0.2 in.), arching upwards.
- Habitat: Broad-leaved forests, old gardens, gardens, hedgerows, roadsides, casually around harbours.
- Flowering time: May–June.
Mustard family plants are known for the shape of their flower: four petals and six stamens, of which two are shorter than the rest. Garlic mustard’s fruits (siliquae) are also typical of the family: long and slim. Thankfully it is easy to recognize garlic mustard within the large Mustard family group because of its leaves, which are initially a rosette of egg-shaped leaves with rounded (crenate) teeth in its first growing season, developing in the second year into cordate and sharp-toothed leaves on the ascending flowering stem. The net-like veins on the underside make all the leaves look slightly wrinkled. Garlic mustard looks even more impressive due to its habit of growing quite a dense patch of shoots. The leaves wither soon after flowering and the whole plant looks a lot less stylish.
In Finland garlic mustard grows as a native plant mainly in the oak belt, on the Åland Isles and in the south-westernmost archipelago. It has spread with people, deliberately or naturally, to old populated areas in southern mainland Finland. Garlic mustard is particularly fond of areas that have been settled for a long time – medieval towns, the centre of old parishes and the ruins of manor houses – and it has not spread to more recently settled areas. The influence of people and animals on old cultural areas has gradually seasoned the soil to make it loamy and nitrogenous. Places like this do not really exist in Finland outside long-settled areas, and garlic mustard is incapable of surviving out in the wild.
Some garlic mustard stands are remnants of the times when it was cultivated: it is an old useful plant which can be eaten young in salads and it was also collected in its time as a medicinal. Its scientific generic name Alliaria comes from genus Allium because when the young leaves are rubbed they smell like onion or garlic.