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Lettuce
(Lactuca sativa sp.)


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Cultivars

Even in winter, but of course especially in summer, a good salad is a treat for body and soul. And, while specialty salads—from a fresh sliced tomato with a little chive, parsley, olive oil, and vinegar to a beet-and-walnut salad—are many and pleasing, lettuce remains the bedrock of the salad-lover’s crops. But there are lettuces and there are lettuces….


Lettuce Types

There are a myriad of lettuce types, differing one from another in ways large and small. The most useful high-level classification is this:

Within each broad type there are numerous variants, but we like to think of each as being divided into two sub-classes: “green” and “red”—where “red” rarely means more than purple-tinged or bronze (as with the “red” Sierra Batavian pictured above).


Choosing Cultivars

As you see below, we discuss both warm-weather lettuces (always the greatest problem with these heat-hating vegetables) and cold-weather lettuces. If you, like us, would like a steady, year-round supply of lettuce, you will need to succession-plant through the year, adjusting your sowing choices as you move through the seasons. Keep in mind that the rough average for lettuces is about 8 weeks to maturity and adjust your seeding varietal choices for how the weather will be over the next 8 weeks from the sowing date. You should also do some homework to determine how many lettuce plants to grow. If you feel you would like a fresh head every other day—a not unreasonable average—and the average growing time is 8 weeks (56 days), then you will need to have 56/2, or 28, heads in various stages of growth from just-seeded to harvest-ready. Obviously, you need to adjust that for your own tastes, whether you need a head daily or just one a week, or whatever; but the rule of thumb is 56 divided by how many days between heads. (Mind, it’s never going to work out that smoothly: individual heads may grow faster or slower than expected, not every type is even nominally just 56 days of growth, and some can be harvested on a continuing cut-and-come-again basis; but at least it provides you a rough framework for reckoning.)

Summer Varieties

With some moderate care in the handling of our growing area—as described farther down this page—one should be able to grow lettuce all the year round. Lettuce is a cool-weather crop to begin with, and is pretty cold-hardy. While it certainly can’t grow out in the snow, only modest aid should be needed to keep it going. More difficult is summer growing, as lettuces notoriously bolt (go to seed) very quickly in hot weather. The answer there is (we hope and believe) modest protection, such as partial shading, but first and foremost careful selection of cultivars known to be heat-resistant.

A great help here are the results from the Colorado State University’s Lettuce Bolting Resistance Project. We don’t have to rely on seedmen’s claims or individual anecdotal accounts: we have careful, methodical trial results available.

The general summation of the trials was this:

The Batavian lettuce varieties outperformed the other varieties of lettuce by far. They did not bolt all season long, even in the warmest days…The Butter varieties also performed well.

Thus, the Batavians are the undisputed kings of heat resistance, far ahead of all other types; runners up are the butterhead types. In summer (or really warm parts of spring and autumn), it seems just folly to try growing any other varieties; indeed, in the peak-heat days, even butterheads may be better avoided. (A ways back, just barely plausible, are the Romaines; leafy types don’t do at all well in heat; and heading lettuces are notoriously intolerant of really hot summer conditions—besides, we already know that they are scarcely worth the home gardener’s putting her or himself out for.)

The best Batavian types for summer uses seem to be green Concept and red Cardinale. For butterhead types, among the best green types is good old Buttercrunch, while the choice for a red type seems to be Bronze Mignonette.

For the stubborn, who want to see if they can defy the odds, the best summer Romaine types are probably the green Jericho and the red Cimarron (sometimes listed as Cimmarron). If you’re really adventurous, you could even ventue a crisphead, the aptly named Summertime. Looseleafs are probably wasted effort in summer heat, and in any event we see no need for them with all the other many delightful types out there. (YMMV; but, if so, do your own homework.)

Winter Varieties

Though seed houses make much of certain “cold-hardy” winter lettuces, in truth all lettuces are, by nature, fairly cold-hardy. Rather than shop for especially cold-hardy types (and thus have to have two sets of lettuce seeds, one for hot and one for cold), it makes more sense to try to ameliorate winter growing conditions, something we discuss a bit farther on. Curiously, Batavians, so good in heat, are also pretty resistant to frost, as to a fair degree are butterheads—so one needn’t look for special varieties of those types other than the ones already discussed above under “Summer”.

But if your fancy for lettuces is insufficiently satisfied by Batavians and butterheads, in cooler weather you can mix in Romaines and even, if you like, a crisphead. For Romaines, your best bets are probably those same ones listed above with summer lettuces: green Jericho and red Cimarron. If you want to go a crisphead, the above-cited Summertime seems a good choice (depite the name). For loose-leaf lettuces, you’re on your own, as we see no point to them with all the other more interesting types available.


The Growing Area

In spring and fall, lettuces can be grown outdoors with no special considerations. But if we are to succeed in the cold of winter and the heat of summer, we need to take some measures.

Winter

As we said above, lettuces are by nature cool-weather crops—they supposedly can withstand air temperatures down to perhaps as low as 20° F., so in a region where our average coldest overnight low is 15° F., we don’t need measures so drastic as an actual greenhouse. There are all sorts of “tunnel” and “hoop” systems, of varying degrees of complexity and sophistication (and cost), or you can fake it up on your own. Fortunately, lettuces grow pretty close to the ground, so plant height is not an issue. Another helpful trick is to place transparent quart (or liter nowadays) soda bottles filled with water in among the plants; those will heat up in the sunny day and release the heat at night (a poor man’s version of Walls o’ Water, plus it doesn’t surround the plant).

Summer

To mitigate the warmth, the simplest thing is to provide some shade. A crude way is simple latticed slats set up on the south, east, and west ends of your greens-growing bed. Or you can get fancier by putting up (in the same places) sunshade fabric, of the sort used on house outsides over windows in the summer; or perhaps plastic window-screen roll (fairly inexpensive) would work. If you get relentless sun, make the east and west end coverings solid.


Planting

Timing

We will take it as an assumption that by the means described above, we in this climate (and anyplace the same or warmer) can be growing lettuces throughout the year. To simplify matters, we will also assume that each lettuce will be taken as a whole when ready, though in reality some are “cut and come agin” types from which we take leaves without pulling the whole plant; the idea is just to get a grasp on numbers.

We already ran through the math a little above on this page, but will repeat it here. If you want a steady, year-round supply of lettuce, you need to succession-plant through the year, adjusting your sowing choices as you move through the seasons. Keep in mind that the rough average for lettuces is about 8 weeks to maturity and adjust your seeding varietal choices for how the weather will be over the next 8 weeks from the sowing date. You should also do some homework to determine how many lettuce plants to grow. If you feel you would like a fresh head every other day—a not unreasonable average—and the average growing time is 8 weeks (56 days), then you will need to have 56/2, or 28, heads in various stages of growth from just-seeded to harvest-ready. Obviously, you need to adjust that for your own tastes, whether you need a head daily or just one a week, or whatever; but the rule of thumb is 56 divided by how many days between heads. (Mind, it’s never going to work out that smoothly: individual heads may grow faster or slower than expected, not every type is even nominally just 56 days of growth, and some can be harvested on a continuing cut-and-come-again basis; but at least it provides you a rough framework for reckoning.)

Actual nominal days to maturity (from direct seeding) for the lettuce types we recommend:

As you see, the warm-weather types are distinctly earlier than the cold-weather types. (Whether the same type will grow differently in warmth and in cold, we just aren’t sure.) Thus, in warm weather, where the average maturity time of the lettuces you are growing is more like 7 weeks (49 days), 28 heads may be a bit much: the reckoning would only suggest 24 heads. But a little extra does no harm, and it might well be that you want more than a head every other day in warm weather, when salads are especially attractive.

As you go along, play it by ear and your developing experience; before long, the flow of lettuce will become fairly steady.

Sowing Seeds

Though many always do lettuces from transplants, it is not problematic to direct-seed for most of the year. The limits, in terms of soil temperatures, are not below 40°F. and not above 80°F. Those are the limits: is is better practice to limit direct seeding to a soil-temperature range of 45° to 75°. (You do have a soil thermometer, yes?) If your soil temperatures seem en route to going outside that range, switch to starting and transplanting seedlings—but remember that you need to be looking ahead on that temperature by the average seeding-development time, which is typically something like 3 to 4 weeks; just subtract the seedling-growth time from the listed “days to maturity from direct seeding” figure to see when to start seedlings.

From seed sowing to germination is around 7 to 10 days. The first leaves to show are the plants’ “baby teeth” (cotyledons), and will soon be followed by true leaves. When the seedlings are showing a set or two of true leaves, put them into the peat (or cow) pot you will transplant them in, wait a week or two, then harden them off for two or three days, then transplant into their final home.

Space lettuces in one-square-foot spots.

The Bed

Lettuces are “greedy feeders”, so be sure that the soil is good and rich for them. Something like 1 to 1½ pounds a square foot of compost or well-composted steer manure every year or two is a good idea (that’s a layer about ½ to 1 inch thick). Though we hope to get lettuces (and other salad greens) growing year round, it’s wise to move the lettuce bed at least annually, to minimize soil-disease risks. (Remember our suggested four- or five-bed rotation plan.)


Growing

Keep them watered well and, perhaps above all, regularly: irregular watering may be worse than scanty watering. Pick lettuce when it looks ready. Grow enough that you can afford to pick when the individual plants are of a modest size, lest you run the risk of having them bolt on you. Many leafy kinds can be harvested a few leaves at a time, which they will then grow back—what’s called “cut and come again” harvesting.


More

Relevant Links

Besides any links presented above on this page, the following ought to be especially helpful.


Odds and Ends

Biology

All the lettuces are from the Asteraceae (formerly Compositae) family, the asters, which includes many edible greens and some edible roots.

History

There are today literally thousands of different cultivars of lettuce—all sprung from ancestral wild lettuces that grew (and still grow) in Northern Europe, Asia, North Africa, and even parts of North America. There is good evidence that some sorts of lettuces were being cultivated in Egypt as early as 4500 B.C. Certainly the Babylonians were cultivating it by 3,000 years ago, and the Chinese may have started growing it before them.

Herodotus tells us that lettuce was served on the tables of the Persian kings of the 6th century B.C. In the 5th and 4th centuries B.C., other great Greek writers described and praised its virtues. The Greeks called it tridax, the Persians kahn. The plant’s modern “scientific” (Latin) name, Lactuca, is derived from the Latin root word lac, milk; our English word “lettuce” derives from the French laitue, also meaning milk. That, obviously, is because the plant has a heavy, milky juice. The juice, or sap, was long thought to have significant medical properties: Hippocrates mentions lettuce sap as a medicinal, supposed to induce sleepiness.

By the first century after Christ, Roman writers were describing a dozen distinctly different lettuce types, some of which were fairly common; it is known that lettuces much resembling present-day Romaine cultivars were then being grown. (It was popularly believed in the time of Augustus that he was cured of an illness by eating lettuce.)

As in the development of the cabbages, the primitive forms of lettuce were loose, leafy, and sometimes “stemmy” types; the looseheading and firm-heading forms occurred much later. Firm-heading forms had become well developed in Europe by the 16th century, but just when they were first developed is unknown. The oak-leaved and curled-leaf types, and various other colors now known, were all described in the 16th and 17th centuries in Europe.

Columbus evidently carried lettuce to the New World, for its culture was reported on Isabela Island (now called Crooked Island) in the Bahamas in 1494. It was common in Haiti in 1565. When it was introduced into South America is not known, but doubtless it was soon after the Europeans arrived; it was under cultivation in Brazil before 1650.

Lettuces are today used almost exclusively raw, but they can be cooked—indeed, lettuce was normally eaten cooked till the time of Louis XVI, when the Chevalier d’Albignac famously dressed raw lettuce with a vinaigrette.

Envoi

Think lettuce, for all its virtues, is boring? Check out The Lettuce Ladies (this being the 21st century, female readers can check out The Broccoli Boys).


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