Lemongrass

Lemongrass is essentially pest and disease free outdoors, but plants brought inside for winter are prone to spider mites. Check leaf undersides for fine stippling and webbing. Knock a light infestation off with a forceful spray of water, or treat with insecticidal soap. Hot, dry indoor air is exactly the condition spider mites breed fastest in, and the pest that never troubled the plant in the garden becomes its main winter problem the moment it comes through the door.

Plant divisions or nursery starts outdoors once all danger of frost has passed and nights are warming, spacing them 3 feet apart in full sun. Expect almost nothing for the first few weeks, then rapid growth once real summer heat arrives. Lemongrass is a tropical grass with no frost tolerance, and it stalls until soil and air are genuinely warm. A well-fed clump reaches 3 to 6 feet tall and 3 feet wide, so crowded plants shade each other out of the thick stalks you actually harvest.

Through the warm growing season, water plants in the ground with a half-strength balanced soluble fertilizer about once a month; feed plants in containers the same solution weekly. Water regularly and avoid letting containers dry out, but do not leave the soil waterlogged. Lemongrass is a grass and pulls heavy nitrogen to build leaf and stalk. Bulk is the crop here, so the size of the clump by season's end is a direct function of how much water and nitrogen it got while it was hot.

Harvest any time a stalk reaches about half an inch thick. Cut it off at ground level, or push an outside stalk to the side and twist and pull it free. Take the oldest, outermost stalks first, and use the bulbous bottom few inches. Taking the outer stalks first opens the center of the clump and pushes the plant to throw new shoots, so the same clump keeps producing instead of going woody. Thickness, not calendar age, is what tells you a stalk has laid down usable flavor in its base.

When you harvest or lift the clump before the first frost, set aside a 6 inch section of the bulbous shoot base with roots attached. Split it into pieces, pot them in good potting soil, and grow them on in a warm, bright window over winter; move them back out after frost danger passes. Fresh grocery-store stalks with an intact root plate will also root in a glass of water in about two weeks. Lemongrass is propagated by division rather than seed in practice, and each shoot base carries its own root plate, so one summer's clump is next summer's whole planting for free.

Harvest or dig the clump before overnight temperatures reach freezing. Outside zones 9 to 11 lemongrass will not survive winter in the ground, so either treat it as an annual and take the whole harvest, or lift it and bring potted plants indoors as temperatures cool, keeping them in a warm, bright, sunny spot. Frost kills or severely damages this tropical grass outright, and there is no dormancy to wait out. Everything you have grown all summer is standing in the open when the first freeze arrives.