By Wendy MacLean, Master Gardener
A trio of reasons motivate me to grow lettuce (Lactuca sativa) indoors: the carbon footprint of transporting lettuce long distances to my home; the shocking price of one head of lettuce at grocery stores in the winter; and the memory of a family member being sickened by E. coli a few years earlier, at the same time health authorities had issued warnings about imported lettuce.
What influenced me to sow the lettuce seeds when I did was my craving for “greens,” which begins in February during our long Prairie winter. Since many seed packages state that the “baby leaf” stage is reached about 30 days from sowing and “full size” at 45–60 days, I chose the dates of December 13 and 14 to sow my seeds. In this way, I calculated that I could begin eating fresh, home-grown salads by early to mid-February.
What you need
Growing lettuce indoors requires consideration of the containers, growing medium, seeds, and plant care needed to ensure success.
Containers. I retrieved four clean rectangular planters, 61 cm or 81 cm long by 20 cm wide by 15 cm deep (24 in. or 32 in. long x 8 in. wide x 6 in. deep), and a few smaller plastic containers saved from a store-bought BBQ chicken. A depth of 15 cm (6 in.) is adequate for lettuce’s shallow root system. Ensure that all containers have good drainage holes, to avoid soil waterlogging and root rot. Place the containers on trays to catch any excess water. If you plan on harvesting just a few leaves every couple of days, grow one to three plants in a 20‑cm (8‑in.) pot.
Soil. I used a good-quality potting mix for the initial sowing of seeds in smaller containers. For the direct-sown ‘Ovations Mix’ and for transplanting the lettuce seedlings into the larger planters, I used about two parts of this potting mix moistened to the damp sponge stage and one part of moist, good-quality compost gently mixed into the top 5 – 7.5 cm (2 – 3 in.) of the growing medium. This compost helps retain moisture and adds nitrogen. (Leafy greens grow quickly and need sufficient nitrogen.) If the growing medium has no fertilizer, feed them a balanced fertilizer every two weeks or so after true leaves appear. Try a balanced 10-10-10 or 5-5-5 water-soluble or granular fertilizer, diluted to half strength. I, however, found that the addition of compost provided sufficient nutrients.
Seeds. My stack of partly used seed packages from the previous summer provided ‘Black Seeded Simpson’, a loose-leaf lettuce (Lactuca sativa), and ‘Buttercrunch’, a butterhead type (Lactuca sativa var.capitata1). To give my salads variety, I also chose ‘Ovations Mix’ (Brassica spp.), which is a combination of red mustard (Brassica juncea), mizuna (Brassica rapa), tatsoi (Brassica rapa), kale (Brassica oleraceae),and arugula (Eruca sativa).
I initially sowed the seeds into the smaller containers for later transplanting at the true-leaf stage into larger planters, to ensure that no blank spaces were left where seeds did not germinate. This also helped me space the plants with adequate distance between them, as it is very easy to sow the small seeds too closely together. Since the seed package for the ‘Ovations Mix’ stated that these do not transplant well, I sowed these directly into one larger planter.
Photo: Wendy MacLean – Young lettuce seedlings in first container
READ MORE
By: Florence Carey, Master Gardener
