Mint

Plant early in the growing season, setting each plant into a bottomless container sunk so it extends 3-4 inches above and 10-15 inches below the soil surface. Space plants at least 2 feet apart. Buy plants or take cuttings and divisions rather than sowing seed if you want a named type, since seed rarely comes true. Mint travels by underground rhizomes that root as they go, and once it is loose in a bed it is nearly impossible to eradicate. The collar has to sit proud of the soil because the runners will also creep over a flush rim.

As new growth pushes in spring, give each plant about one teaspoon of a balanced 16-16-16 fertilizer. That is the whole year's feeding. At soil prep, work in no more than 1 inch of well-composted organic matter per 100 square feet. Mint is vigorous enough without help, and pushing it harder backfires: over-fertilizing produces soft crowded growth that promotes rust and actually lowers the leaf oil that gives mint its flavor.

Every 3 to 4 years, lift and divide the clump and replant the vigorous pieces. Do this in spring before growth starts, or alternatively in early fall. Move the divisions to a fresh spot rather than back into the same soil. Dividing every 3 to 4 years is what keeps a mint planting vigorous. Rotating the planting to new ground at the same time is the recommended cultural control for the verticillium wilt and anthracnose that home growers cannot spray for.

When flower spikes begin to appear, cut the stems back to within 1 inch of the soil. Leaves destined for drying are best taken right at this point. The plant will regrow and you can take about three such cuttings a season. Between cuttings, pinch off flower spikes as they form. It is very difficult to over-prune a mint plant. If mint is allowed to bloom, the oil content in the leaves decreases and the leaves are less flavorful, so the same leaf is worth less after bloom than before it. Removing flower spikes as they appear is what holds the flavor.

Give up to 1 to 2 inches per week depending on heat, exposure and soil. Use drip irrigation if you can; if you water overhead, do it before midday so the foliage dries. Do not overwater. Mint rust needs leaf wetness to infect, so foliage that stays damp through the night is what lets it in. Overwatering also dilutes the oil in the leaves along with encouraging the disease.

Before winter, cut each plant back to the ground. Pull out and dispose of any diseased plants entirely rather than replanting them, and rotate the planting area if anthracnose or verticillium showed up this season. Cutting mint to the ground before winter is the extension-recommended way to discourage overwintering pests and diseases, and pruning healthy plants to the ground in fall is listed as a control for anthracnose alongside removing diseased plants and rotating planting areas.