How To Grow Spearmint
To grow spearmint, you will be growing a perennial in zones 3 to 11. Spearmint grows well in full sun to part shade and prefers moist fertile soil. Spacing: 18 to 24 inches apart. Plant size: 24 inches tall.
Researching the mint family, I found that these perennials spread through underground stems (rhizomes) as well as seeds.
When you grow spearmint, which are especially nasty, they will weave a network of tough, quarter-inch-thick rhizomes under an entire flower bed, spilling out into a large section of lawn, sending up a new plant every inch or two from the underground nodes. You can pull up yards and yards and yards of the ropey invaders, but they still keep coming. Gardner beware!
Peppermint and spearmint are beneficial to cabbage, kohlrabi, broccoli, and the other kales by repelling or distracting cabbage fly, ants, and cabbage looper. Spearmint is noted for its ability to repel or distract ants and aphids.
Seeds are poisonous if ingested. Mint may become a noxious weed and invasive. Mints are known to attract bees, butterflies and birds. Aromatic foliage. Suitable for containers.