Lettuce is one of the first crops harvested in spring, reaching maturity before the frost is even off the ground. Leaf lettuce varieties do not form a large head but instead produce leaves that you can harvest as needed from the main plant. These lettuces thrive in containers, allowing you to start the crop before the garden bed has even thawed out completely. Instead of traditional planters, grow leaf lettuce in grow bags. These bags of soil provide all the benefits of a container garden without the expense.
Lay a large bag of compost on its side in an area that receives six to eight hours of sunlight a day. Knead the compost in the bag, breaking up any large chunks and loosening it.
Poke a row of holes in the top of the bag, spacing the holes 2 to 3 inches apart. Flip the bag over so the holes are on the bottom and shape the bag into an even mound.
Cut a rectangle out of the top of the bag with a utility knife. Avoid cutting too closely to the edge, otherwise the compost spills out of the bag.
Create a ¼ inch deep furrow in the exposed compost with the eraser of a pencil. Create additional furrows along the length of the bag, spacing each furrow 4 inches apart.
Sprinkle the lettuce seeds into the furrows, sowing approximately 10 seeds per 1 foot of furrow. Cover the seeds with compost then water the soil until the excess begins to drain from the bottom of the bag.
Thin the seedlings once they sprout so the plants are spaced 4 inches apart along each row. Pinch off or pluck the extra seedlings from the compost.
Water the lettuce once every one to three days, or when the compost in the bag just begins to feel dry. Water at the base of the plants until the excess water drains from the bottom of the bag.
Fertilise the lettuce every two weeks with a soluble 20-20-20 analysis fertiliser, applied at the package recommended rate.
Empty grow bags with premarked planting and drainage holes are available at garden centres. Use these in conjunction with your own homemade compost and potting soils. Add the compost to the garden or your compost pile after the lettuce crop is harvested.