Lepidium sativum - Garden Cress is probably one of first vegetable we grow as children because it takes very little time from sowing to harvest.
It is an annual herb with small green lance shaped leaves that are peppery in aroma and taste.
It is used in salads and sandwiches or as a piquant garnish, often together with mustard.
If left and not harvested it bears small white flowers in early summer.
If you haven't tried growing it then it worth a try.
Sow seeds in a saucer on wet on kitchen paper or a piece of wet cloth on the windowsill but don't let paper dry out.
An alternative for the younger gardeners fill empty egg shells with soil, paint a face on the egg and sow the seeds on the soil, in no time you egg person will have green hair!