These cool-loving plants will grow fairly rapidly, regardless of the variety, and thrive in spring weather. For a continuous harvest, try to stagger your plantings so that a new row gets planted every 2-3 weeks. This will produce plants that mature over a longer period in early summer for a steady supply of greens.
Just about all lettuce varieties are annual plants, and when the days are long and warm in summer, they will “bolt.” This is when their vegetative growth is finished, and the plants are driven to send up tall flower spikes, bloom, and then produce seeds. When the ground is warm in mid-summer, lettuce seeds do not germinate well. Once the plants bolt, the leaves become tougher and bitter – not good for eating – so timing your lettuce harvests before and after mid-summer is wise.
By September, the days are noticeably shorter, and the nights cooler, so lettuce is also an ideal fall crop. Sow fall lettuces from mid-July to late September, and stagger the plantings like you did in the spring for another continuous harvest.
Stubborn growers (a wonderful and inspiring bunch of people, by the way) have devised a few methods to delay bolting and improve germination in warm summer weather. Bolting can be delayed (not prevented) by erecting shade cloths near the rows, so the plants and the soil they’re growing in stay a bit cooler. This can add 1-2 weeks of summer harvesting. Summer lettuce seeds can also be started indoors, in the coolest part of the house. One other trick is to place the seeds on a damp paper towel, and place this inside of a zip-lock bag in the refrigerator for 3 or 4 days. The seeds will germinate, but the seedlings must be delicately placed into soil for growing out. Tweezers come in handy with this method.
Lettuce may be the ideal vegetable for gardeners who lack full sun. It will grow well in partial shade or in dappled light because the plant only wants to produce leaves. This may also delay bolting. Lettuce has relatively shallow roots, so it’s quite well suited for containers. Just provide ample drainage and ample water, and you should be able to grow full heads of lettuce on the smallest patio.
Because of its preference for cool weather, combined with its ability to grow under less direct sunlight than other vegetables, lettuce does very well in winter if you can provide some protection from the elements. Raised garden beds work particularly well for winter lettuce because of the added drainage and generally warmer soil. Cloche protection over a growing row can keep lettuce in fine form all winter long.
Lettuce is a wonderfully versatile vegetable, and it’s probably the easiest of all vegetables to grow. Keep seedlings and mature plants moist, watch for slugs and snails, and otherwise it should perform well. Choose a soil that is loaded with organic matter. A slightly acid to neutral pH (6.0 – 7.0) is ideal. 1 cup of complete organic fertilizer for every 10’ of row will provide ample nutrition throughout the plants’ short lives. A failure to keep the soil moist will result in bitter tasting leaves, so keep a close eye on moisture levels.
As if lettuce wasn’t the ideal crop on its own, there are literally scores of varieties to choose from. There are four basic forms of growth for lettuce:
- Roundhead lettuce grows into a loosely packed heads, and includes the butterheads and Bibb styles. Generally, the leaves are soft, succulent and flavourful.
- Crisphead lettuces also form slightly loose rosettes like the roundheads, but with crunchier leaves, growing more upright, often with appealing variations in colour.
- Looseleaf lettuces have open rosette heads, with their outer leaves falling nearly parallel to the soil. The leaves of this type have narrower stems, and are a little easier to harvest a bit at a time, by plucking each one. Looseleaf types come in an amusing array of shapes, making them excellent for mixed salads.
- Romaine lettuces grow upright, with quite stocky leaves, and they want more fertility and light than other lettuce types.
Because lettuce grows so quickly and goes to seed so easily, it is the perfect vegetable for breeding in variety. Though nearly every lettuce is open pollinated and they’re all the same species, there are hundreds of varieties available. And this is nothing new, by the way. When he retired from the presidency, Thomas Jefferson grew 19 varieties on his homestead in Monticello. By growing several at once, it’s easy to create colourful salads with a wide range of flavours and textures for much of the year.
A great way to experiment with lettuce varieties is to pool your seed order with some friends and then divvy up the seeds so that everyone can have a full range. Over time, you’ll discover some that work for you, and some that don’t. So grow a couple of rows of the standards you like, and then try a row or two of mixed varieties you’re not as familiar with. Variety is the spice of lettuce, after all.
One final tip that we like to recommend is to start lettuces indoors, whenever possible, in seed planting flats. The 128-hole flats work particularly well, even if you’re not filling them up. By planting one seed per cell of these flats, you’ll know exactly how many plants you’ve got – lettuce transplants very easily, so you can shift the tiny plants into the row with precise spacing, rather than seeding the row and then thinning. In the long run, despite the extra work of caring for the seedlings, this ends up being quite economical.
(Family: Lettuce, Asteraceae)