Lettuce Grow Plant. Lettuce seeds can be sown straight into the garden (or pots) or you can start them off in trays or punnets first. The elevated beds heat considerably more quickly than the ground around them.
In the spring, you should be able to get a head start, and in the fall, you should be able to harvest later. For nutrients, leafy greens like lettuces require more nitrogen than other plants since nitrogen is best for stimulating leaf growth. Due to adequate protection being provided by the greenhouse so you can start planting without waiting for the last spring frost date.