Lemongrass

Lemongrass is a tropical grass that grows with startling speed once the soil warms. In a single season it can reach four feet tall and produce dozens of citrus-scented stalks — but it will not survive a frost, which means most gardeners north of zone 9 treat it as an annual with one important exception: you can dig up a division before the frost and keep it alive indoors through the winter.

The most practical way to start lemongrass is to buy a stalk with roots still attached from a grocery store or Asian market. Set it in a glass of water on a sunny windowsill, and in two weeks it will usually produce enough new roots to pot up. A rooted stalk planted in spring becomes a harvestable clump by midsummer. Transplants from a nursery work the same way, and starting from seed is possible but slow — most gardeners skip it.

Wait to transplant until the soil is genuinely warm — four weeks after your last frost is a safer bet than two. Lemongrass planted into cool soil will sulk for weeks and may develop rust-colored leaf tips, a sign that it is stressed. The same plant moved into seventy-degree soil will establish quickly and begin sending up new shoots within ten days. Full sun and consistent moisture produce the fastest growth; a dry week can slow the plant noticeably.

Harvest generously once the clump is established. Cut stalks at ground level when they are at least half an inch thick at the base — the lower white portion is what you want for cooking. Regular cutting encourages the plant to produce more stalks, and a mature clump can handle losing a quarter of its mass every few weeks. The outer stalks are tougher than the inner ones; peel away the fibrous outer layers until you reach the tender core.

Before the first frost, dig up the entire clump and pot a division — a section with five or six stalks and a good root ball. Trim the foliage back to about six inches, water it well, and move it to a bright indoor spot. It will not grow much over the winter, but it will survive, and you can transplant it back outdoors the following spring. A lemongrass plant that overwinters indoors for two or three seasons tends to produce larger clumps each year than one started fresh from a grocery stalk.

The most common failure is leaving the plant outdoors too long in fall. A single night below freezing will kill the foliage and often damage the roots enough that the plant will not recover. Dig it up a week before you expect frost, not the day after.