Apiaceae: A rare upright, hairless perennial, with solid, ridged stems to 1m. Favours damp, grassy places, often found by the coast. White flat topped umbel to 6cm across, flowering from May-August. The seeds are swollen and corky, and give the plant its name. Scarce and found in Southern England only. Native to most of Europe, including Britain, from Belgium south and east to Spain and Western Asia.
The root is said to be edible. Starchy with a flavour somewhat like filberts, is much esteemed in some areas. I have never tried it myself.
Requires a moist or wet fertile soil in a sunny position. Sow seeds spring in a cold frame. When they are large enough to handle. Easy.