Marjoram is a tender perennial in the mint family, closely related to oregano but milder and sweeter, with a scent of pine and citrus. It is the herb for egg dishes, sausages, dressings and anything where oregano would be too coarse, and it is used fresh and dried; the flavour is strongest just before the knotted flower buds open, which is why the old name is knotted marjoram. It grows 12 to 18 inches.
In cold-winter zones it is grown as an annual or overwintered indoors, since it does not survive freezing. It germinates slowly and resents cold, so start seed indoors eight weeks before last frost or buy plants, and set them out 6 to 8 inches apart once the soil has warmed, in full sun and lean soil that drains; rich ground and shade reduce the fragrance. Pinch the growing tips to keep plants bushy and delay flowering. Harvest in the morning, before the heat lowers the oils.
Cut whole stems just as the buds form and dry them in bundles; marjoram dries well and keeps its flavour. Let a plant flower at the end of the season and the bees arrive. A pot brought indoors in fall to a sunny window gives fresh leaves through winter. Deer and rabbits leave it alone. Native to the eastern Mediterranean.
Damping Off
Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.
Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.
Root rot
Plants wilt, yellow, and stunt even in moist soil; lower stems and roots turn brown, soft, and mushy and the plant may collapse. Most common in heavy, wet, or poorly drained ground.
Improve drainage and stop overwatering, and never plant too deep. Lift and destroy badly affected plants along with the soil around the roots. Grow in raised or free-draining beds to prevent it returning.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Spider Mites
Tetranychus urticae →Fine stippling or bronzing on leaves, faint webbing on undersides, foliage drying out during hot, dry weather.
Spray foliage with a strong jet of water to dislodge mites. Apply insecticidal soap or horticultural oil to leaf undersides; repeat every 5–7 days as needed.
Aphids
Aphididae →Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.