It is a joy to grow herbs. I have enjoyed it very much. Here are some tips for growing spearmint in your garden.
You will want to sow outdoors in the springtime, in a sunny to partial shady location. Make sure all danger of frost is past. Light aids in the germination process, so make sure to barely cover the seeds with a light layer of soil. You can sow seeds earlier if need be, or if you desire. 8 weeks before the last frost in your area, you can start seeds indoors.
Plant seeds no deeper than 1/4 inch, and space apart aproximately 12-18 inches. They grow to about 2-3 feet. They are a perennial plant.
Harvesting the Spearmint:
Harvest the leaves as they mature. If you choose to dry the leaves, the plants can be cut back to about 3 inches above the soil line, JUST before their flowers open. Engery in the plant can be put back into making more and new leaves, as opposed to exerting a lot of energy to make seeds, etc.