Quick answer
Sow lettuce little and often in cool, moisture-retentive soil. Thin or transplant plants to the spacing their mature form needs, protect seedlings from slugs and keep the root zone evenly moist. Harvest loose leaves regularly or cut whole heads as soon as they are firm enough to use.
Heat, long days, drought and root disturbance can accelerate bolting. Select cultivars for the season, use afternoon shade in hot periods and avoid sowing more than can be harvested promptly. Lettuce quality depends more on continuous, unstressed growth than on heavy feeding.
Choose a lettuce type
Loose-leaf lettuce forms open rosettes and supports cut-and-come-again harvesting. Butterhead has tender leaves and a soft heart. Cos or romaine forms upright heads with a crisp midrib. Crisphead types, including iceberg, need more space and time to form dense hearts.
The RHS lettuce guide notes that loose-leaf types can produce a first picking in about a month, while hearting lettuce may take up to three months. Choose fast loose leaves for small spaces and continuous picking; grow heads where there is room to let the plant reach full size.
Cultivars are often labelled for spring, summer or winter culture. That label matters. A heat-tolerant summer lettuce and a hardy protected winter lettuce respond differently to temperature and day length.
Site and soil
Use an open sunny position in cool weather and a site with afternoon shade when summers are hot. Four to six hours of direct sun can produce useful leaves, but deep shade encourages weak growth and prolonged leaf wetness.
Lettuce prefers fertile soil that drains freely while holding moisture. Incorporate mature compost into poor soil and aim for a tested pH around 6.0–7.0. Avoid concentrated fertiliser and fresh manure around a crop eaten raw.
The University of Minnesota Extension treats lettuce as a cool-season vegetable. Use local temperature patterns rather than a fixed month: a protected winter sowing and a midsummer sowing need different cultivars and care.
Direct sowing and transplanting
Sow thinly in a shallow, pre-watered drill and cover lightly. Lettuce seed can germinate poorly in high soil temperatures, so shade the seedbed temporarily or sow in modules in a cooler position during heat. Keep the surface damp without waterlogging it.
Make short sowings every one to three weeks rather than a single large row. Thin loose-leaf plants to about 15cm and larger heads toward 30cm, using the seed packet for the final spacing. Crowded plants stay small, trap moisture and are harder to inspect.
Transplants should be young and actively growing. Harden them, preserve the root ball and plant with the crown at soil level. Deep planting can trap water around the growing point and cause rot.
Containers and small-space growing
A broad container at least 30cm wide can hold several loose-leaf plants or fewer hearting lettuces. Use clean peat-free potting compost and ensure free drainage. Shallow window boxes work for baby leaves if they are checked frequently for water.
Containers allow the crop to be moved into light shade during a heatwave, but black pots can heat the root zone quickly. Water in the morning where possible and do not leave the compost permanently saturated.
For indoor salad leaves, provide strong light and airflow. A bright window may support young leaves, but weak winter light will not produce dense heads without supplemental lighting.
Watering, feeding and bolting
Keep moisture steady from germination to harvest. Drought makes leaves tougher and can trigger premature flowering; a sudden flood after wilting does not reverse the stress. Water soil rather than the heart and allow foliage to dry before night.
Rich garden soil rarely needs additional feed for a short lettuce crop. Container plants can receive a weak balanced liquid feed if growth pales after several harvests. Do not use strong high-nitrogen solutions, which can create soft growth without correcting poor light or damaged roots.
Bolting begins when the stem elongates and a flower stalk forms. Leaves usually become bitter. Harvest promptly at the first sign. Future prevention means a better seasonal cultivar, steadier water, cooler roots or a different sowing window—not cutting off the flower stalk after the change has begun.
Protecting and diagnosing the crop
| Symptom | Likely causes to investigate | First checks |
|---|---|---|
| Seedlings disappear overnight | Slugs, snails, birds or cutworms | Slime, clipped stems and time of damage |
| Plant elongates and tastes bitter | Bolting from heat, long days or stress | Cultivar, temperature and watering |
| Brown leaf margins | Heat, salt buildup, dry roots or tipburn | Container salts, root moisture and airflow |
| Lower leaves rot at soil level | Poor airflow, deep planting or saturated soil | Crown depth, spacing and drainage |
| Leaves have winding pale tunnels | Leaf miners | Mines, larvae and affected leaf age |
| Rosette remains small | Crowding, low light, cold or root damage | Spacing, sun and root condition |
Wash harvested leaves thoroughly, but use pest identification rather than spraying by default. Physical barriers, habitat management and removing badly affected leaves are often sufficient in a small crop. Follow current local food-crop labels for any treatment.
Harvest and handling
Pick outer loose leaves while leaving the centre to regrow, or cut a whole head just above soil level. Harvest in the cool morning when leaves are crisp. Do not leave mature heads waiting for maximum size in warm weather; quality can decline quickly.
Cool leaves soon after harvest, wash in clean water and dry them before refrigerated storage. Discard slimy or decaying tissue. Lettuce is a short-storage crop, so succession sowing is more useful than trying to preserve a large glut.
Record cultivar, sowing date, first harvest and when bolting began. Those four values reveal the most reliable seasonal windows for the site.
Sources and review basis
- How to grow lettuce — Royal Horticultural Society
- Growing lettuce, endive and radicchio — University of Minnesota Extension
Season labels and spacing on the seed packet take precedence where they are more specific. Adjust shade and sowing intervals to observed temperature.