Classic cottage garden and woodland flower, beloved by humans, bees and fairies alike and one of the first signs that summer is on its way. Flowers in early summer and lasts through the whole season. If the spikes are left to go to seed, they will become feeders for birds and be high rise habitat for tiny insects. Readily self seeds once you get them established and they should just come back and flower for you each year. Biennial which means they flowers in the second year, so if you sow in Autumn they flower the following summer.
To guarantee having plants and establish them in new areas, we usually sow some seed in a well wetted peat free compost in a seed tray. Make sure not to cover the seed as they need light to germinate. A bag or a piece of glass over the seed tray will help keep the moisture in until they germinate. Once they have sprouted up and are large enough to grab the leaves of each seedling between your fingers and with the gentle aid of a pencil or something similarly pokey, ease them out and replant into a module tray to grow on. We would normally start this process in Autumn after we have collected the seeds and we let them grow on in the poly tunnel through winter to plant out n the spring to flower that year. Any shelter or cold frame is good for this but they are a hardy enough plant that they may be fine outside too. You could use the same method and sow the seed in the spring time or early summer but you’d be waiting til the following year either way for the flowering spikes. There too is always the option of just throwing the seeds directly onto the ground where you want them to flower and obviously the cleaner the soil the better chance you would have for them to grow.