Lettuce – January 2017 Plant of the Month

The first homegrown salad of the season is an eagerly awaited treat, made from tender lettuce picked fresh from the garden. As long as hungry rabbits and woodchucks don't beat us to the harvest, spring planted lettuce is usually a pretty trouble-free crop in most parts of the country. Lettuce growing gets a little more challenging as summer heat arrives, but with some planning and proper selection of varieties many of us can still enjoy a summer salad from our garden even as the temperatures rise. And with a bit more planning in mid to late summer the harvest can continue into the fall, possibly even into the winter months. So lettuce get growing!

Varieties: The days when lettuce in a salad meant a wedge of iceberg lettuce are long gone. There is an amazing range of lettuces you can grow, from tender butterheads and frilly leaf lettuces to crispy romaines and – yes – even heads of iceberg. Also long gone is the notion that lettuce doesn't have much to offer in the nutrition department. Like other leafy greens, lettuce, especially dark green types like romaine, is a good source of healthful antioxidants, folate, and vitamins A and K – all for very few calories.

  • Red leaf lettuce

    Leaf lettuces are among the quickest and easiest lettuces to grow, with some varieties ready for harvest in just a month and a half. This non-heading type of lettuce can be harvested by picking individual leaves or by cutting the entire plant. Leafy varieties are also some of the prettiest lettuces you can grow. Leaves may be frilly, deeply lobed or smooth, and green or red in color.

  • Romaine lettuce, also called cos, forms loose, upright heads of crisp, elongated, dark green or red leaves that are tops among lettuces in the nutrition department. The essential ingredient for Caesar salad, romaine is also delicious grilled. Harvest the lettuce so that the heads stay together; then cut the heads in half lengthwise and brush them with vinaigrette dressing. Grill until lightly browned all over for a tasty, but unusual vegetable.
  • Butterhead lettuce forms loose heads of succulent, tender leaves. Also called Bibb or Boston lettuce, these are the easiest head lettuces to grow. Some varieties have very soft leaves, while others, often referred to as summer crisp varieties, have a crisp, juicy texture.
  • Head lettuce, also called crisphead lettuce, includes the familiar Iceberg lettuce. The crisp, juicy leaves of these varieties taste great in salads, but this type is the most challenging for most home gardeners to grow. It needs a long growing season of cool weather to do best. Look for newer cultivars that are more tolerant of higher temperatures during the growing season.
  • Romaine Lettuce

    Mesclun, which means "mixture" in French, is simply as assortment of leafy salad greens that are harvested at a young stage. While different kinds of lettuces are typically included in a mesclun mix, other greens are included as well, such as arugula, beets, chard, kale, mustard, and cress. Mixes containing a variety of different types of seeds are available, or you can make up your own custom mix from individual kinds of seeds if you choose

Site: Full sun is best, but you can still get a respectable harvest if your garden only gets 4-6 hours of direct sun a day. Plant in well-drained, fertile soil that has been amended with compost or other organic matter. Lettuce does well grown in containers and its attractive leaves make it a good choice for an edible landscape planting.

When to Plant: For the earliest harvest, plant lettuce seeds indoors about 4 weeks before it's time to set hardened off transplants out, which can be as early as 4 weeks before the last spring frost date in your area. You can begin direct seeding as soon as your soil can be worked in the spring. For early spring planted crops select varieties that mature quickly so plants are ready to harvest before the weather turns hot.

For late spring and early summer planting, select varieties that have been bred for heat tolerance. Look for varieties that resist bolting and tipburn. Plant summer lettuce where it will get some shade from taller or trellised crops, or erect a shade cloth cover over the lettuce bed.

Iceberg lettuce

To figure out when to start plants for fall harvest, note the days to maturity listed on the seed packet of the variety you've selected. Lettuce grows well in the cool days of fall, but it also grows more slowly as days get shorter, so add about 14 more days to this number. This will be the number of days to count back from your average fall frost date to arrive at your planting date. Mature lettuce plants are more sensitive to freezing temperatures than small transplants, but if you provide some protection with row covers or a cold frame, you can extend your harvest season longer into the fall. Also, select varieties that have been bred for cold tolerance.

Planting: Lettuce does not store well, so plant a small amount every 7-10 days. This way you'll have a continuous harvest, but you won't be left wondering how you're going to eat ten heads of lettuce at once! Scatter lettuce seeds in wide rows or plant in rows, spacing seeds about 1 inch apart. Barely cover the seeds with fine soil (1/4 inch deep), as light helps seeds germinate. Thin seeds as recommended for the variety you are growing, adding the thinnings to salads.

Broadcast mesclun seeds in a wide row. You'll be harvesting mesclun when the plants are small (4-6 inches tall), so you can sow thickly and don't need to worry about thinning. Simply cut off the plants just above the soil surface. You can often get one or two more harvests from the same plants as they regrow. Like lettuce, mesclun does best in cooler weather, making it great for quick crops in fall and spring.

Culture: Make sure lettuce plants have consistently moist soil, especially when the weather is hot. Gardeners in the warmest areas may need to take a break from the lettuce harvest in the heat of summer. One problem you may run into is that the soil is still too hot for good lettuce seed germination in late summer when the fall crop needs to be started. Try starting seeds indoors in a cool spot or shading the planting bed prior to seeding so the soil is cooler when the seeds go in the ground.

Red leaf lettuce

Troubleshooting: Aphids feeding on lettuce can cause leaves to turn yellow and become distorted, and they may also transmit virus diseases. Cabbage loopers and other caterpillars, slugs, and birds also find lettuce appetizing. Covering the lettuce bed with lightweight row covers excludes many pests. Be sure the edges are well-sealed where they meet the soil to prevent any interlopers from sneaking under.

Watch out for rabbits. Of course, they will happily feed on many other veggies in your garden, but they seem to regard lettuce especially as an all-you-can-eat salad bar planted for their benefit. If rabbits are a problem in your garden, a 2 foot high, small gauge wire fence is the best way to keep them out. Extend another foot of the fencing below ground, with 6 inches going straight down vertically and 6 inches bent away from the garden at a right angle (like an underground L-shape) to prevent rabbits from digging under.

Harvesting: To harvest lettuce at the “baby” stage, simply pick off the outer leaves once plants are 4-6 inches tall, leaving the inner leaves to continue growing. You can also cut off all the young leaves at once, leaving a 1-inch stump. Give plants a dose of soluble fertilizer and in a few weeks you’ll be able to cut a second harvest. Or you can let lettuce grow into mature heads, cutting the entire head at ground level.

Lettuce Eat! Here's a fun snack idea kids will love: Ladybugs on a Leaf from the Kitchn.

Fun Facts

The ancient Greeks believed that eating lettuce made you sleepy and so they served it at the end of a meal. This belief is echoed by beloved children’s author, Beatrix Potter, in The Tale of the Flopsy Bunnies: “It is said that the effect of eating too much lettuce is 'soporific'.” 

The scientific name of lettuce is Lactua sativa. “Lactua” means “milk-forming” and refers to refers to its milky white sap.

Lettuce was first brought to the New World by Columbus on his second voyage in 1494.