Important notes
heat / long days: In heat lettuce bolts: it sends up a stalk, the leaves turn bitter and ooze white latex. Keep it cool and harvest young.
Light
Bright, 12–14 h; dislikes harsh heat.
Watering
Evenly moist; drought stress turns leaves bitter and triggers bolting.
Temperature
Cool: 14–22 °C. Above 24 °C it bolts and turns bitter.
Humidity
50–65 %. Too humid favours leaf rots.
Target values by method & stage
| Stage | pH | EC (mS/cm) | Water °C | Air °C | Humidity % | Light h | Duration (days) |
|---|---|---|---|---|---|---|---|
| Germination | 5.8–6.2 | 0.4–0.8 | 16–20 | 15–20 | 60–70 | 14 | 5 |
| Seedling | 5.8–6.2 | 0.8–1.2 | 16–20 | 14–20 | 55–65 | 14 | 14 |
| Vegetative | 5.6–6.2 | 1.2–1.8 | 16–20 | 14–22 | 50–65 | 14 | 30 |
| Harvest | 5.6–6.2 | 1.2–1.6 | 16–20 | 14–20 | 50–60 | 13 | 35 |
| Stage | pH | EC (mS/cm) | Water °C | Air °C | Humidity % | Light h | Duration (days) |
|---|---|---|---|---|---|---|---|
| Germination | 6.1–6.5 | 0.4–0.8 | — | 15–20 | 60–70 | 14 | 5 |
| Seedling | 6.1–6.5 | 0.8–1.2 | — | 14–20 | 55–65 | 14 | 14 |
| Vegetative | 5.9–6.5 | 1.2–1.8 | — | 14–22 | 50–65 | 14 | 30 |
| Harvest | 5.9–6.5 | 1.2–1.6 | — | 14–20 | 50–60 | 13 | 35 |
| Stage | pH | EC (mS/cm) | Water °C | Air °C | Humidity % | Light h | Duration (days) |
|---|---|---|---|---|---|---|---|
| Germination | 5.8–6.2 | 0.4–0.8 | 16–20 | 15–20 | 60–70 | 14 | 5 |
| Seedling | 5.8–6.2 | 0.8–1.2 | 16–20 | 14–20 | 55–65 | 14 | 14 |
| Vegetative | 5.6–6.2 | 1.2–1.8 | 16–20 | 14–22 | 50–65 | 14 | 30 |
| Harvest | 5.6–6.2 | 1.2–1.6 | 16–20 | 14–20 | 50–60 | 13 | 35 |
Common problems
Bolting in heat, tipburn from calcium deficiency/fluctuating moisture, aphids, downy mildew.
Pests & diseases
| Pest / Disease | Symptom | Organic treatment |
|---|---|---|
| Aphids | colonies under leaves | rinse off, beneficials |
| Slugs | holes in young leaves | hand-pick, slug collars |
| Downy mildew | yellow patches, grey mould beneath | spacing, airflow, avoid overhead watering |
Edible parts
- Leaves · edible from Vegetative
Yield techniques
Harvest whole or "cut-and-come-again" — take outer leaves and let the heart keep growing.
Propagation & pollination
- Method
- seed
- Germination time
- 7 days
- Germination temp
- 15-20 °C
- Sowing depth
- 0.3 cm
- Pollination
- self
- Hand pollination needed
- no
light germinator — barely cover
Companion planting
🟢 Good neighbours: Coriander (Cilantro), Dill, Garden strawberry
Flavor
mild, fresh, crisp
Storage
In the fridge, wrapped slightly damp.
History
Lettuce was grown in ancient Egypt and was sacred to the fertility god Min. Today it is the world's most important salad plant.
Nutrition
Folate, vitamin K and lots of water — low in calories.
Sources
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