Lettuce: Sowing, planting and harvest calendar
How do you sow lettuce under cover?
Choose a variety suited to the season and your climate. Fill a tray or individual modules with moist seed compost, using containers with drainage holes. Sow thinly and cover lightly according to the packet instructions, rather than burying the seeds deeply. Keep the compost slightly moist without saturating it.
Place the seedlings in good light and ventilate the shelter to avoid overheating: high temperatures can prevent some varieties from germinating. Once seedlings have a few true leaves and are easy to handle, move those sown together into individual modules. Gradually acclimatise them to outdoor conditions before planting out when conditions suit the variety; protect them if cold weather is forecast. Check for slug damage on young plants and choose protection according to the problem observed.
Label each batch with its variety and sowing date so you can distinguish heading lettuces from loose-leaf types. Prefer small successive batches to sowing one large tray at once: fewer plants will be ready together. Turn the tray if all the young stems lean towards the window, so light reaches them more evenly.
How do you sow lettuce outdoors?
Choose a variety suited to the season and sow when the soil is workable, neither frozen nor waterlogged. Prepare a fine, weed-free seedbed in fertile, well-drained soil. A sunny spot suits cool periods; in hot weather, light shade during the hottest hours helps limit overheating and drying.
Sow thinly in shallow drills about 1 cm deep, with roughly 30 cm between rows, following the packet instructions. Water gently and keep the seedbed moist without saturating it. Once seedlings are established, thin gradually to the recommended spacing, usually about 15–30 cm depending on the type. This is the final plant spacing, rather than a compulsory distance between every seed. Sow small batches at intervals when conditions allow, and check young plants for slug damage.
Mark the rows so you can distinguish seedlings from weeds emerging at the same time. Thinning means removing surplus plants to give the others space; work gently so you do not lift their roots. Healthy young leaves removed during thinning can be used in a salad after you have washed them thoroughly.
How do you plant lettuce?
Transplant healthy young lettuces with several true leaves and a well-rooted plug. If they were grown under cover, gradually acclimatise them outdoors beforehand. Choose a variety suited to the season and a spot with fertile, well-drained soil. In hot weather, light shade and planting during a cooler part of the day help limit wilting.
Water the plugs before planting and keep them intact when removing them from their containers. Set them at their previous growing depth, leaving the centre free of soil. Follow the recommended spacing: about 30 cm for large hearting lettuces and 15 cm for small loose-leaf types, adjusted to the variety. Firm gently and water, then check moisture while the plants establish. Protect against cold or pests when needed, according to the forecast and damage observed.
The heart is the central area where new leaves emerge: do not fill it with soil when closing the planting hole. If watering makes the soil settle, check its position again. Keep the variety label nearby so you can match your later harvest to the type, taking a whole head or picking individual leaves.
How to care for this plant
-
Thin seedlings
If your lettuces are crowded and you want whole heads, thin gradually to about 15–30 cm according to the variety. Keep closer spacing for promptly harvested baby leaves. In a module, select the seedling you want to keep.
When do you harvest lettuce?
Harvest according to the lettuce type and its development, rather than a fixed date. For loose-leaf lettuces, pick a few outer leaves from each plant once they are large enough to use, leaving the centre intact. For hearting types, cut the head when it has formed well, before the flower stem elongates. Use a clean knife without pulling on neighbouring plants.
Morning harvesting helps keep the leaves crisp. If you cut a whole plant and want another picking, leave a short stem of about 2–3 cm and keep the growing centre intact; regrowth depends on the type and conditions and is not guaranteed. Use the lettuce soon after picking and keep it cool if needed, without relying on a fixed one-week shelf life. Remove damaged leaves and wash the sound leaves before use.
Watch the middle of the plant: an elongating centre and a developing stalk signal bolting. Do not leave a ready lettuce in the bed unnecessarily while waiting for a bigger head. When picking individual leaves, spread your harvest over several plants so each rosette retains enough foliage to continue growing well.
Lettuce
- Type : Vegetables
- Subtype : Leafy vegetables
- Botanical Family : Asteraceae (daisy family)
Characteristics
- Lifecycle : Annual
- Exposure : Partial Shade
- Frost Hardiness : Slightly Frost Sensitive
- Cultivation Difficulty : Easy
- Mature height : 25 cm
Sowing & Planting
- Greenhouse crops : Unheated greenhouse
- Greenhouse Growing : Not Required
- Sowing Depth : 0.5 cm
- Plant Spacing : 25 cm
- Row Spacing : 25 cm
Maintenance
- Maintenance : Low
- Water Requirements : Moderate
Other characteristics
- Soil Type : Humus-rich
- Soil pH Preference : Neutral
- Pest Sensitivity : Moderate
- Disease Sensitivity : Moderate
- Weed Sensitivity : Moderate
- Pollination : Self-pollinating
- Propagation : Sowing