- Name also: Field Pepperwort, Field Cress
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Annual or usually biennial herb.
- Height: 20–40 cm (8–16 in.). Often 1-stemmed, on top candelabra-like branched, densely short-haired, greyish.
- Flower: Corolla regular (actinomorphic), white, approx. 0.2 cm (0.08 in.) across; petals four, 2–3 mm (0.08–0.12 in.) long. Sepals 4. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence an elongating raceme in fruiting stage.
- Leaves: Alternate, lowest soon dying, stem leaves stalkless, amplexicaul, several. Lowest leaf blades slightly lobed, upper leaves ovate–elliptic, with sagittate base and toothed margins.
- Fruit: Two-seeded, broadly elliptic, flat, with notched tip, broadly winged, virtually glabrous, rough, 4.5–6 mm (0.18–0.24 in.) long silicula. Stalk spreading, at least as long as silicula.
- Habitat: Fields, sandy areas, sometimes mills, harbours, railway embankments, banks, wasteland, land-fill sites, rubbish tips.
- Flowering time: June–July.
Field pepperweed’s sturdily stemmed, evenly-branched inflorescence is reminiscent of a candelabra. This effect is emphasized by the way that the stem’s lowest leaves drop off. Of the mustard family plants that grow in Finland, it bears the greatest resemblance to alpine pennycress (Thlaspi caerulescens; also known as alpine pennygrass) and field pennycress (T. arvense), although these both have glabrous stems while field pepperweed is densely short-haired. Greenflower pepperweed (L. densiflorum; also known as prairie peppergrass) is also shaped like a candelabra, but its stem is often more sparsely leaved. The species can be decisively differentiated by their fruits, which on greenflower pepperweed are only slightly winged.
Field pepperweed’s original habitat was probably in southern Russia, Caucasia and Asia Minor. In Finland the species grows in the south-west of the country and can be found on the Åland Islands and the south-western archipelago. On mainland Finland it grows quite steadily around Turku and Naantali and has temporary stands much further north as well. Pepperwort has clearly decreased in Finland, and permanent stands might have disappeared altogether. The species looks to be establishing itself in new areas, however. In Finland the plant favours sandy fields, gravelly railway embankments, roadsides, harbours, rocky hillocks and it may be found close to mills. Most of the stands in Finland are short-lived by nature: pepperwort is threatened by the encroachment of gritting, asphalt and highways. The industrialization of agriculture and weed-killing has probably also been detrimental in many places. Somewhat paradoxically, field pepperweed’s cultural habitats are at the same time dependent on and threatened by human activity. A few observations have also been made in completely wild areas, and there are stands a kilometre away from the nearest habitation.
Many other types of cress grow locally or casually in the wild in Finland. Smith’s pepperwort (L. heterophyllum) looks very much like pepperwort, but it is a perennial. It is a western European plant that grows on ridges, roadsides and seeded lawns in southern Finland.