- Name also: European Searocket
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Annual herb.
- Height: 15–40 cm (6–16 in.). Stem base branching, glabrous.
- Flower: Corolla regular (actinomorphic), purple (sometimes almost white), approx. 1–1.5 cm (0.4–0.6 in.) wide; petals four, 6–10 mm (0.24–0.4 in.) long. Sepals 4. Stamens 6, of which 2 short and 4 long. Gynoecium fused, a single carpel. Inflorescence a raceme, extending in fruiting stage.
- Leaves: Alternate. Blade pinnately lobed–with leaflets, commonly bipinnately lobed, sparsely toothed, glabrous, fleshy, lobes quite linear, narrow.
- Fruit: 2-seeded, quite flat, fleshy walls, indehiscent, 1.5–2 cm (0.6–0.8 in.) long silicula, tip ovately lanceolate, bristly and quite blunt, upper edge of basal part with 2 protruding lobes. Stalk approx. 7 mm (0.28 in.), spreading.
- Habitat: Sandy areas and seaweed embankments by the sea.
- Flowering time: July–August.
Sea rocket is a coastal pioneer plant in Finland. It is among the first groups of plants to colonise barren sand banks and seaweed heaps by binding soil with its rootstock that would otherwise easily blow away. Sea rocket is abundant around sandy beaches, which it has adapted to: its ribbon-like stands can run along the water-line for hundreds of metres in Yyteri and Kalajoki. It is quite rare, however, on the Åland Islands and the south-western archipelago, and it is casual around the Bay of Bothnia.
Sea rocket has spread from the Bothnian Sea to the shores of Satakunta, Southern Ostrobothnia and Uumaja because the currents in the eastern part of the Bothnian Sea flow northwards. Sea currents are important for spreading the annual plant as its fruit can float and remain viable for several weeks. The tips of the silicula’s two single-seeded parts break off to seek new habitats, and some of them find a suitable sandy beach where the waves deposit the seeds among debris on the beach. The base of the silicula usually sticks to the stalk and ends up at the base of the mother plant to make sure that the species continues to grow in a place that has proved suitable. This results in wide, established, long-lasting stands, and on the other hand bridgehead stands that might consist of only a single plant or only a few.
Sea rocket is a unique phenomenon among coastal plants and the large Mustard family. The subspecies ssp. baltica is endemic around the Baltic Sea – but it doesn’t grow anywhere else in the world. Its characteristic features are deeply-lobed leaves and the pod’s two long, oblique appendages, which make it look needle-tipped.