Sweet Marjoram

Sow indoors about 6 to 8 weeks before your last spring frost date, or direct sow outdoors about two weeks before that date. The seed is very fine, so press it into the surface rather than burying it. Marjoram is slow off the mark from seed and needs a long warm run to make usable leaf, so a cold-climate grower who waits for settled weather outdoors loses most of the harvest season. Starting under cover buys back the weeks the season will not give you.

Move seedlings to the garden after the danger of frost has passed, into full sun and well-drained soil. Marjoram prefers a sandy loam and requires good drainage; it will rot in poorly drained, saturated soils. This is a Mediterranean tender perennial rated for USDA zones 9a-10b with no frost tolerance, and it rots outright in poorly drained saturated soil, so both the timing and the drainage are survival questions rather than preferences.

When the plant starts to bloom, cut it back close to the ground rather than tidying it lightly. It will push a fresh flush of growth for a second cutting. A hard cut at bloom resets the plant out of flowering and back into leaf production, and Illinois Extension notes the second flush of growth tends to be a more desired crop than the first cutting.

Harvest when the ball-like knotted tips appear at the ends of the stems and before the flowers actually open. Cut the leafy stems and air dry them, then store in sealed containers. Leaves can be picked for fresh use at any point in the season. Flavor peaks just before bloom. Once the plant commits to flowering it moves resources out of the leaves, so the knot stage is the narrow window where the essential oil in the foliage is at its strongest.

Once the plant reaches 6 to 8 inches tall, prune it back to force branching. Keep cutting stems back before flowers appear. Marjoram is naturally a low, spreading plant that will run to a few lanky stems and then bloom if left alone. Cutting the growing tips early pushes side shoots and builds the bushy frame that carries the season's leaf.

If you want the plant to live past this year, dig it from the garden before frost and bring it indoors to a sunny window. Below USDA zone 9 it is otherwise simplest to treat marjoram as an annual and resow next spring. Marjoram is a tender perennial that generally will not survive a winter north of zone 9, so the first hard frost is the end of the plant, not a dormancy it wakes from. Container plants brought in often struggle through winter, which is why resowing is the honest fallback in cold zones.