Welsh Onion (Allium fistulosum)
The taste is similar to that of ordinary onions, but you use the green leaves instead as scallions. A perennial onion, that grows in tufts with bunches of thick hollow rounded leaves. It is a bit similar to a bigger version of chives.
In the summer a rounded hollow flower stalk will emerge, ending in a ball of white flowers. This should be cut off so that the plant does not waste energy in producing flowers and seeds. If you cut the flower stalk while the flowers are still buds, it is still soft and can be eaten like the leaves.
Welsh onions can be propagated either with seeds or by splitting the tufts.