How to Grow Lettuce
'Little Gem' from Seed
The restaurant lettuce by name -- a miniature Cos/Romaine with a sweet blanched heart and crunchy outer leaves, combining the best qualities of both lettuce types in a self-contained 10-15cm head; an English heirloom AGM ready in 50-55 days from transplant; succession sow every 2-3 weeks from February to August for continuous harvest; do NOT use a heat mat (seeds enter thermal dormancy above 20°C); protect from slugs; perfect for containers
Lettuce 'Little Gem' is the lettuce that appears on restaurant menus by name -- one of very few salad crops so reliably excellent in flavour, texture, and visual appeal that chefs consider the variety designation worth communicating to customers. An English heirloom from the early 1900s, it combines the crunchy, structured spine and upright head of a Cos (Romaine) lettuce with the sweet, slightly buttery flavour and tender quality of a butterhead -- the best qualities of both lettuce types in a miniature, self-contained package that provides a perfect single or two-person portion in a head 10-15cm tall.
The inner heart -- the pale, blanched, tightly-furled leaves at the centre of the head -- is the gem of the name: sweet, tender, and crisp with a delicate flavour completely unlike the more bitter outer leaves of many larger lettuces. When a Little Gem head is cut in half lengthways and dressed with a good vinaigrette, this heart is revealed as the natural bowl and main attraction simultaneously. For the home gardener, the practical virtues match the culinary ones: Little Gem is compact enough for containers, tolerant of a range of growing conditions, relatively slow to bolt (unusual for a Cos type), and ready to harvest in as little as 6-8 weeks from transplanting. The succession sowing approach -- making a small sowing every 2-3 weeks from February through August -- provides a continuous supply of perfect little heads from late spring through to the first autumn frosts.
Quick Facts at a Glance
Plant Type
Hardy Annual -- cool-season crop; AGM; English heirloom early 1900s
Form
Mini Cos/Romaine; sweet blanched heart + crunchy outer leaves; 10-15cm heads
Days
50-55 days from transplant to full head; 7-10 days germination
Key rule
Succession sow every 2-3 weeks from February to August for continuous harvest
Heat
Seeds enter thermal dormancy above 20°C -- do NOT use heat mat; keep cool
Difficulty
1 out of 5 -- the easiest, most rewarding salad crop from seed
Understanding the Variety
Thermal Dormancy -- Why Cold Matters for Germination
Lettuce seeds have a built-in thermal dormancy mechanism that prevents germination at high temperatures -- above approximately 20-22°C, lettuce seeds cease to germinate reliably and can enter a deep dormancy that is difficult to break. This means: do NOT use a heat mat or propagator for lettuce germination; keep the seed tray at room temperature (15-18°C is ideal); in summer sowings, place the seed tray in the coolest part of the house or even in the refrigerator for 24-48 hours before germination to reset the dormancy mechanism. The germination temperature range for Little Gem is 4-20°C -- it can germinate in cool soil in early spring but fails in warm late-spring or summer conditions without cool treatment.
The Succession Sowing Approach -- Why It Is Essential
Little Gem reaches maturity quickly (50-55 days from transplant) and then holds in good condition for only 1-2 weeks before bolting (sending up a flower stalk, after which the leaves become bitter). A single large sowing produces a glut of heads all ready simultaneously, most of which will bolt before they can be eaten. The solution is making a small sowing every 2-3 weeks: 6-8 seeds per sowing, providing 4-6 transplantable seedlings, producing 4-6 heads ready at intervals throughout the season. This succession approach provides 1-2 heads per week throughout the growing season rather than 30 heads for one week.
RHS Award of Garden Merit
Little Gem holds the RHS Award of Garden Merit -- a recognition that it is consistently reliable, high-performing, and of outstanding garden value in UK growing conditions. For a lettuce variety that has been grown since the early 1900s, retaining AGM status through modern re-evaluation is a genuine endorsement of its continuing excellence. The AGM reflects the combination of flavour quality, reliability, bolt-resistance (unusual in Cos types), and consistency that makes Little Gem the standard against which other mini-Cos lettuces are measured.
Sowing & Growing On
Succession Sow Every 2-3 Weeks -- Do NOT Use a Heat Mat (Seeds Need Cool to Germinate)
Sow 6-8 seeds per batch every 2-3 weeks from February (under glass) through August. Cover seeds 3-5mm deep -- unlike many salad crops, Little Gem does NOT require light for germination but does require cool (15-18°C) temperatures. Avoid heat mats and warm windowsills above 20°C, which trigger thermal dormancy.
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Sow a small pinch of seeds every 2-3 weeks from February (under glass) through August. Sow 3-5mm deep in modules or small trays at 15-18°C -- room temperature, NOT in a propagator. Germination in 7-10 days. Do not use a heat mat -- temperatures above 20°C prevent germination.
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Thin to one seedling per cell or transplant into final position 3-4 weeks after germination. Space 20-25cm apart in rows 30cm apart for full heads; 15cm apart for smaller heads. Alternatively, sow directly in the final position 5mm deep and thin to 20-25cm. Keep consistently moist from germination through to harvest.
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Provide consistent moisture and protect from slugs in the early weeks. Young lettuce seedlings are highly attractive to slugs -- protect with grit, wool pellets, or copper tape from the moment of transplanting. Consistent moisture (not waterlogged) prevents tipburn -- the browning of leaf edges that occurs when dry spells prevent calcium movement to the growing tip.
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Harvest when heads are firm but the heart is still tight -- 50-55 days from transplant. A ready Little Gem head has a slight give when squeezed gently at the top -- not rock-hard (immature) and not soft (over-mature). Cut at the base with a sharp knife, leaving the root in place; a second flush of small leaves sometimes grows from the cut stump.
Growing On & Care
How to Eat Little Gem
The classic restaurant preparation -- cut the head in half lengthways, dress with a good vinaigrette (Dijon mustard, red wine vinegar, olive oil, salt) and serve cut-side up -- showcases the sweet, pale heart to best effect. The combination of the slightly bitter, crunchy outer leaves and the sweet, tender inner leaves in a single mouthful is the distinctive quality of Little Gem that makes it unique among lettuces. It also works well as a warm salad (briefly halved and charred cut-side down in a very hot dry pan), as a vehicle for chicken Caesar dressing, or as a lettuce cup for Asian-inspired fillings.
Container Growing
Little Gem is one of the best lettuce varieties for container growing -- the compact head fits well in a 20-25cm pot, and the relatively shallow root system makes it suitable for window boxes, balcony planters, and deep containers. Grow one head per 20cm container or 3-4 heads in a window box. Keep consistently moist (containers dry out faster than beds) and position in partial shade in hot summer months to delay bolting. Container-grown Little Gem can be positioned near a kitchen door or on a windowsill for on-demand harvest.
Bolt Resistance
One of Little Gem's most valuable practical qualities is its relative bolt-resistance for a Cos-type lettuce. While all lettuces eventually bolt (send up a flower stalk and become bitter), Little Gem holds in good condition for 1-2 weeks after reaching maturity before bolting -- longer than many other Cos types in the same conditions. In hot summers, this window shortens; in cool UK summers, it can extend to 3 weeks or more. Growing in partial afternoon shade in July and August, and keeping soil consistently moist, further delays bolting.
Slug Protection
Slugs are the primary pest of lettuce at all stages, and Little Gem seedlings and young plants are particularly vulnerable. Protect from the moment of transplanting with grit (scattered generously around each plant), wool pellets, copper tape around the container edge, or nematodes applied to moist soil (Phasmarhabditis hermaphrodita nematodes are highly effective against slugs in cool moist conditions). Night checks with a torch during the first 2-3 weeks after transplanting allow early identification and removal of any slugs that breach protective barriers.
Heat and Bolting Management
In a hot UK summer (July-August), Little Gem can bolt more rapidly than in cooler conditions. Strategies to delay bolting: provide afternoon shade (grow in partial shade or use shade cloth over the bed from midday to late afternoon); keep soil consistently moist (dry soil stress accelerates bolting); sow in July-August for autumn harvest when temperatures are declining rather than rising; harvest at the first sign of the central stem elongating upward. The moment the central growing tip begins to rise above the leaf level, harvest immediately -- the leaves are still good quality at this stage but will become bitter within days.
Cut-and-Come-Again Option
Little Gem can also be harvested as individual outer leaves rather than as a complete head -- a cut-and-come-again approach that extends the harvest from any single plant. Begin harvesting outer leaves when they are large enough (typically 3-4 weeks after transplanting) by removing the largest outer leaves while leaving the inner head to continue developing. This approach provides salad material for 2-3 weeks before the head matures for final harvest. The outer leaves have more texture and slightly more bitter flavour than the sweet inner heart -- both have their place in a salad bowl.
Sowing & Harvest Calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
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| Sow under glass (Feb-Mar) |
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| Sow outdoors (Apr-Aug) |
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| Harvest (Apr-Oct) |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Seeds not germinating | Temperature too high; thermal dormancy | Do not use a heat mat. Maintain 15-18°C during germination -- room temperature in a cool room or unheated greenhouse is ideal. In summer (July-August), pre-chill seeds in the fridge for 24-48 hours before sowing to reset thermal dormancy. Germination 7-10 days in correct conditions. |
| Lettuce bolting before harvest | Heat; dry conditions; plant too mature | Harvest promptly when heads are firm -- Little Gem holds 1-2 weeks after maturity, not more in warm conditions. In summer, grow in afternoon shade to delay bolting. Succession sow every 2-3 weeks so fresh seedlings are always ready to replace plants that have bolted. |
| Tipburn (brown leaf edges) | Uneven watering; calcium deficiency | Maintain consistent soil moisture throughout the growing period -- both drought and waterlogging cause tipburn. Water at the base of plants in the morning. On acid soils, apply a light dressing of garden lime to improve calcium availability. Tipburn is primarily cosmetic and does not affect the inner heart. |
| Slug damage | Slugs feeding on young plants | Protect with grit or wool pellets from transplanting. Night checks with a torch during the first 2-3 weeks allow early slug removal. Nematodes (Phasmarhabditis hermaphrodita) applied to moist soil provide effective biological control in cool conditions. |
Plant Specifications
The perfect little head every week -- succession sow every 2-3 weeks at cool room temperature and harvest the sweet heart all season
Sow 6-8 seeds at cool room temperature (15-18°C -- never a heat mat) every 2-3 weeks from February. Transplant at 20-25cm spacing. Keep consistently moist and protect from slugs. Cut the firm head at the base at 50-55 days. The sweet pale heart is the gem. Repeat the sowing every 3 weeks for fresh heads all season.
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