Country diary: a rocket propelled by wind and water

Sea rockets’ roots find moisture deep in the sand, nourished by nutrients from decayed seaweed. Photograph: Phil Gates

The tide had turned and I walked up from the water’s edge, past tangled heaps of kelp cast up by autumn gales, then over soft, dry sand that is wetted only by extreme equinoctial spring tides. In a corner of the beach, between the promenade and the pier, I found a patch of sea rocket, Cakile maritima, still in full bloom.

This maritime member of the cabbage family, with lilac-coloured flowers that emit a delicate carnation fragrance, thrives in this toughest of seaside environments. It’s under constant threat of burial by wind-blown sand but is dependent on the sea, transported around our shores by coastal currents in much the same way that coconuts are carried between coral atolls.

Sea rocket flowers and seed pods. Sand burial stimulates elongation of its flowering shoots. Photograph: Phil Gates

As soon as I touched its stems, several ripe spindle-shaped seedpods fell and were whisked away in the wind towards the incoming tide. These are the species’ lifeboats, buoyant and waterproof, surviving at sea with their cargo of seeds for months until a spring tide carries them ashore, to germinate in the sand.

Sea rocket, an annual, blooms once, then sometimes disappears for years, until waves sow fresh seed on the strandline. Two years ago, I noticed a few isolated specimens at the top of Whitburn beach, about a mile away, and it was probably their pods that made the short journey to this sheltered haven.

But this plant is capable of much longer voyages. In 1963, when the volcanic island of Surtsey first appeared above the waves 20km south of Iceland, sea rocket was the first flowering plant to colonise its barren shore, floating across from a coastal colony on the mainland. It is a worldwide traveller, distributed beyond its natural range after being carried to new oceans in ships’ ballast.

Despite its ubiquity on Britain’s sandy beaches, it seems to have no place in our folklore, nor has it acquired vernacular names or been used as food or medicine. John Gerard, in his herbal of 1597, lumped it together with other rockets, commenting that they all “maketh a good sallet herbe” and “stirreth up bodily luste”, but beyond that, nothing.

A Flying Dutchman among wild flowers, making fleeting appearances on the shore, wandering the oceans until doomsday.