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Lettuce Explain: A Guide to Greens

Have you noticed that there are different types of lettuce out there? Lettuce can be grouped into one of several main growth types – looseleaf, bibb (sometimes called boston or butterhead), romaine (cos), batavian (also called summercrisp), and iceberg (crisphead). You may notice leaf shape descriptions for some types (for example, oakleaf is the shape of some kinds of looseleaf lettuce). You may also see young lettuce sold at markets described as “leaf”, while this relates more to the planting and harvesting methods rather than the growth type.

Harvest techniques matter! Here is a red romaine that was harvested incorrectly. It has begun to bolt and will never form a tight head.

Harvest techniques matter! Here is a red romaine that was harvested incorrectly. It has begun to bolt and get bitter and will never form a tight head.

Within each type there are different varieties. For example, ‘Bronze Arrowhead’ is the lettuce variety, while the growth type is looseleaf. Each type of lettuce has unique qualities that suit it for different dishes and, especially important for Chicagoland, different kinds of weather. Different growth types also means different harvesting methods.

While some may advocate for harvesting just the outer leaves of any lettuce to prolong the harvest, you’re going to have a better quality lettuce to eat when it’s clear-cut. Prolonging the harvest is a good idea for long-growing greens like collards, mustard, chard, and kale, but lettuce tends to get bitter and may bolt when left to grow too long.

Leaf lettuce is usually a looseleaf type, planted very close together. Each small plant will only produce a few leaves before running into the neighboring lettuce plant. This close spacing helps keep the lettuce greens small and tender. They are harvested all at once, when about 3-4″ tall, about 2″ from the soil surface (a knife is the handiest tool for doing this). The bottom 2″ of the plant will regrow in a few weeks, providing another harvest for your salad.

Leaf lettuce is often planted closely together. This encourages the 'baby size' greens.

Leaf lettuce is often looseleaf type planted closely together. This encourages the ‘baby size’ greens.

When planting any lettuce other than leaf lettuce, be sure to leave enough space between each plant to allow the lettuce to reach full size. This information will be on your seed packet. Heading lettuces can be expected to weigh about one pound when fully grown.

Young red romaine at the Edible Treasures Garden at The Field Museum.

Young red romaine at the Edible Treasures Garden at The Field Museum. Each is 6-8″ from the neighboring plant.

Clear-cutting romaine, butterhead, batavian, buttercrunch and iceberg lettuce means you’ll get one harvest from each plant, but you’ll have a large, full-sized head to make your salad.

'Tropicana' looseleaf lettuce, weighing about 13 ounces after cutting the main stem.

‘Tropicana’ looseleaf lettuce, weighing about 14 ounces after cutting the main stem. Each looseleaf lettuce was planted about 12″ from the neighboring plant.

How to harvest lettuce that forms a head:

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The taproot is located below the main stem.

Locate the main stem at the soil surface. This is what you are going to cut with a harvest knife or snips.

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Oozing

After cutting, you may see a milky fluid oozing out of the stem. This is a sticky, natural latex in the plant called lactucarium and is common in the stem. (It’s a natural plant defense against chewing insects!). As the plant matures and gets ready for seed production, more of the latex is produced in the leaves, giving the lettuce a bitter taste. If you’re unsure whether your lettuce is past it’s prime, tear off a small leaf toward the top of the plant. If latex oozes from the leaf, this is a good sign the whole plant will be bitter.

While all lettuces grow well in cooler spring and fall weather, some types will also do well in summer’s heat. We’ll have several kinds of lettuces available at our plant sale, and expert gardeners to help you pick out the best variety for your dishes. For more information, check out Johnny’s Selected Seeds for great suggestions on early, mid-season and late-season lettuce varieties