Lemon Grass

Cymbopogon citratus
Half hardy Perennial
Ht 60cm 
Tall grass with sharp edged leaves, white bulbous base - both the leaves and stems are edible, so there's no need to harvest the stalk; just trim and chop the fresh leaves.
It grows incredibly quickly during the Summer months and benefits from being potted up.
For the first time I managed to over Winter a pot of this on the windowsill at home, kept dry and looking very dead it came back to life during the May sunshine when I started to cut and water it!