How to Grow Leeks
A tip sheet on how to grow and care for leeks.
Leeks (Allium porrum)
- Family: Alliaceae (Onion)
- Hardiness: Hardy
- Ease of growing: Medium
- Nutrient needs: Medium
- Water needs: High
- Common propagation: Transplants
- Germination temperatures: 40°F to 95°F
- Germination time: 14 to 21 days
- Viability: 1 to 5 years
- Weeks to grow transplants: 12 to 16
- Start: February to March
- Plant out: May
- Typical spacing: 4” to 6” on 24” rows
- Plants per square foot: 4
- Days to harvest: 75 to 120 from transplants
Leeks are not common in most gardens. This onion relative is grown for its thick, white stems that possess a sweet and subtle onion flavor. Leeks are extremely hardy and perform well in Michigan. They will grow in most well drained soils as long as they receive a dependable supply of moisture.
Varieties vary in their color, winter hardiness and days to maturity. Tadorna is a popular high-yielding variety with a long white shank, blue-green color and good winter hardiness.
Preparation and planting
Leeks take a long time to grow, so transplants are often started beginning as early as February, when seedlings that are at least 8 inches tall and pencil-thick will do best.
You can start transplants in a trench 6 to 8 inches deep. As the plants grow, fill the trench with no more than 1 inch of soil at a time. This will yield the desired long, white stems. If the filling is done too fast, the stems may rot. The other growing option is to plant the seedlings like onion transplants and hill up around the stems as they mature. Control weeds around young plants – they are slow to establish and cannot compete against vigorous weeds, especially if the weather is hot.
Insects: Onion thrips, oinion maggot, bulb mite.
Diseases: Basal rot, white rot, downy mildew, botrytis rot.
Harvest and storage
Harvest leeks whenever they reach a usable size, usually 1 inch in diameter or larger. At full maturity, they may reach 2 inches in diameter. Pull by hand or dig them out. Before freezing sets in, remove leeks from the garden and store under cool (32°F to 40°F) and moist conditions, packed upright in boxes of moist peat or sand and stored in a basement, or mulch them heavily for storage over the winter in the garden. Leeks are biennials, so plants left in the garden the next spring will develop flowers and seed heads, at which point the flavor changes and they become undesirable to eat.
Developed by James Manning, Undergraduate Research Assistant, and Daniel Brainard, Vegetable Extension Specialist; MSU Department of Horticulture; Gary Heilig, MSU Extension educator.