This is my 1 year old lemon balm, grown from seed. Makes a lovely tea, helps calmes nerves and hyper children. Use aprox 4 leaves, in just boiled water - leave for 3 mins, then remove leaves. I add 1 tsp of sugar - but can also use honey to sweaten. It is very refreshing, the calmness effects works quite quickly. The plant is a perrenial, but will die right back in winter. But has survived last year's snow - so quite hardy.
You can dry the leaves or freeze them for winter use.