Lemon Balm (Melissa officinalis)

This non-native plant from the mint family has long been revered for its subtle citrus taste and numerous health benefits, namely when used as a tea to aid digestion after a meal or to reduce stress levels. So great for a bedtime cuppa! 
This plant escapes into the wild from gardens due to its sprawling growing habit and can be found colonising shady, slightly damp area by hedgerows or roadsides in large numbers.
Other than tea, Lemon Balm makes a great addition to desserts, puddings, an interesting twist to a mojito or my personal favourite, as a substitute for lemon grass in oriental stir-fry's and curries.
Look out for it's dark green leaves.