The biggest hurdle lettuce growers have is starting lettuce seedlings during the heat of summer – our tip is to start them in the coolest part of your greenhouse, garden, or even inside. We’ve even heard of market gardeners popping ice blocks on seed trays to keep the soil cool during heat waves.
1. We like starting most of our seeds in seed trays, soil block or biodegradable pots with a fine seed raising mix, but you can direct sow lettuce seeds in a pot or garden space that gets six to eight hours of direct sunlight. If direct sowing, just remember to not sow if the weather for the next seven days reaches 28 degrees Celsuis or above. If the weather outlook looks warm, its best to start lettuce seeds in seedling trays in a cool place.
2. Sow your lettuce seeds just under the surface of the soil and sieve around 2mm of seed raising mix over the top.
Slightly mist the soil with the hose while being careful not to move the soil covering the lettuce seed.
3. Ensure that the lettuce seeds stay moist by watering the soil as many times as required.
In winter this could be every second day but in summer up to four times a day could be required. If a lettuce seed germinates under the soil surface but then the soil dries out, the tiny germinated seedling will also dry out and die and never show its head above the soil.
4. In winter, lettuce seedlings may require some extra nutrients like a foliar spray but during warmer months you’ll have seedlings ready to be transplanting in a matter of three to four weeks.
5. Once your seedlings are large enough to handle and pull out of their seedling cell with roots and soil intact, its time to plant them into the garden. If you have been growing your lettuce seedlings indoors or undercover it is best to move the seedling tray outside in the elements for up to a week to allow the seedlings to ‘harden off’. This process allows the lettuce seedlings to get use to the warmth of the day and cool of the night before they also endure the shock of being transplanted.
6. When transplanting your lettuce, plant at approximately 30cm apart in a checker board pattern. This spacing allows the lettuce to grow to its full potential without being crammed in like a sardine!
7. Lettuce can grow to full size in as short as six weeks in summer and up to four months in the cooler months. During the warmer months lettuce can ‘bolt’ or go to seed quickly, so it is best to pick and succession plant your lettuce more regularly than you do in the cooler months.
8. Succession planting of lettuce is the secret to having lettuce all year round! Succession planting is simply sowing lettuce seeds at regular intervals to ensure you always have seeds germinating, lettuce seedlings ready to transplant, and of course lettuce ready to harvest. In summer, we suggest sowing lettuce every two weeks to ensure a constant supply for lush summer salads.