Sowing leeks: nursery, transplanting and timing
Plan a leek crop from sowing through transplanting, with practical nursery, spacing and aftercare cues for the harvest season you want.
By Marmanda4 min read
For a UK garden, the RHS suggests sowing leeks outdoors in spring, raising them in a nursery row and transplanting once the seedlings are established. Its winter-leek example takes about six months from sowing to harvest. Choose the harvest season first, then reserve space for both the nursery and final row.
What harvest season are you planning for?
The RHS leek guide gives March and April as the main outdoor sowing period in the UK. It describes winter leeks as a longer crop, taking around six months. These are reference points for British conditions; the variety and local season affect the route, so use the seed packet and regional advice when planning elsewhere.
The French SNHF leek sheet illustrates how the target harvest changes the method: nursery sowing from March to May for autumn harvest, sowing under cover in February or March for summer, and sowing in place in August or September for spring. SNHF says to thin that sowing and, if needed, transplant in October or November. These dates describe a French system, not a month-by-month conversion of the UK RHS window.
Starting in a nursery keeps small seedlings out of the main bed until they can be moved. The French SNHF's August–September route is sown in open ground as a starting row, then thinned and optionally transplanted in October–November; only plants not moved stay in that original row. Under-cover sowing is another option where protection and light are available. Choose according to available space, the variety and the harvest season.
How should you sow a nursery row?
Prepare a fine, workable seedbed and open a drill about 1.5 cm deep. The RHS recommends rows 30 cm apart. Sow thinly, cover the seed and water gently so it stays in place. Label the variety and sowing date. Keep the surface moist while seedlings establish, but do not leave the bed waterlogged.
Remove weeds while they are small and avoid letting seedlings form a dense clump. A nursery row should make it possible to lift young plants with their roots intact. The RHS describes transplanting after about two months, once plants are around 20 cm tall. That is a size and timing cue within its method, not a guaranteed growth rate for every garden.
If you sow under cover, make sure seedlings receive light and ventilation. Protection can help with an early start, but it does not remove the need to monitor moisture and plant growth. The vegetable sowing and planting calendar provides seasonal context without replacing the instructions for your variety.
How should young leeks be transplanted?
Water the nursery row first if the soil is dry, then lift plants carefully rather than pulling them by the leaves. In the RHS method, either thin plants to 15–20 cm along the row or move them into holes about 15 cm deep, with 15–20 cm between plants and 30 cm between rows. These are RHS UK measurements for its method.
The SNHF uses a different French criterion for spring-sown plants: transplant when stems exceed 4 mm in diameter, at 10 cm along the row and 40–50 cm between rows. It says deep transplanting helps form a longer white shank but gives no numerical planting depth. Do not combine the RHS height cue and holes with SNHF spacing as if they were one protocol. Follow one complete method and adjust it to the variety and site.
In the RHS method, make a 15 cm hole, stand the leek in it and fill the hole with water; the RHS says not to backfill. The water settles soil around the roots. Keep the leaves above the surface; the planting depth concerns the stem and roots, not the growing centre. For bought plants, follow the supplier's preparation instructions rather than adding a trimming step from another method.
How do you care for the crop after transplanting?
Check soil moisture as plants establish and water when the bed needs it. In the French SNHF method, earthing up is done about three weeks after planting to blanch the stem; draw soil up gradually while keeping the leaf centre clear. This operation applies to established plants, not seedlings still in the nursery.
Record variety, sowing method, transplant date and harvest period. Comparing those notes over seasons is more useful than treating the six-month estimate as a promise. The beginner's vegetable-garden plan can help reserve a nursery strip and the final rows.