Lettuce is an interesting crop and I find it does best if you sow it directly in the garden. If you start it early (directions below) then be careful when transplanting or you’ll lose the starter plant. With their small roots and large leaves they can lose a lot of moisture very quickly on a hot day (particularly if you wreck their roots when transplanting.)
When to Plant
Sow seed outdoors .6 cm deep, from as soon as you can get onto the garden (late April) and then every week thereafter.
If you want to start them indoors, start your seed in individual cell packs or peat pots approximately six weeks before you want to put them into the garden.
Where to Plant
In full sun in soils high in organic matter.
How to Plant
Sow approximately one seed per centimeter of row and thin them out as they grow so that the mature lettuce has 20-30 cm of space. Note the thinnings are perfect for eating! Successive plantings each week will give you a regular amount of lettuce to harvest.
On indoor sowing, remember that you do not want to disturb the roots of transplants if you start them early, so space the seedlings well and thin to one per cell or jiffy pot. Keep the seed warm for the first few days but once germinated, the lettuce plants should be grown at no less than 15C.
Care & Maintenance
Leaf lettuce is far easier to grow than head lettuce and I’d recommend it as a first effort in lettuce. You’ll always get useable leaves while with the heads, sometimes things happen (like slugs or the head splits etc) to wreck the crop. Note that those perfect heads you see in the supermarket are often hydroponically or greenhouse grown. Leaf lettuce growing follows the same rules but the harvest is done by taking a leaf or two from the outside of each plant. Do not pull up the plant but allow it to keep producing new fresh leaves for harvest.
You should be able to harvest a mature, outer, leaf per week from each plant; this should tell you how many plants to grow.
Once the heat of the summer hits lettuce can go bitter, particularly if you water-stress it. So, keep the water flowing and plan on a fall sowing for fall harvests when the weather turns cool again.
(all numbers rounded out)
1/4 inch = .6 cm
1/2 inch = 1.3 cm
1 inch = 2.5 cm
6 inch = 15 cm
12 inch = 30 cm
18 inch = 45 cm
36 inch = 91 cm