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growing lettuce

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  • Lettuce of all kinds thrives in cool temperatures and consistently moist soil, so spring and fall, when temperatures are between 45 and 75 F, are the best times to grow them
  • Tips for growing, harvesting and addressing common pests and lettuce plant diseases are included
  • Harvesting your lettuce while still immature is a simple way to get more nutrition out of it. After two to three weeks of growth, it’s considered a microgreen, which is packed with higher densities of nutrients than the full-grown version
 

How to Grow Great Lettuce

April 14, 2017 | 154,279 views

By Dr. Mercola

If you're growing your own vegetables, now is the right time to start your lettuce. Lettuce of all kinds thrives in cool temperatures and consistently moist soil, so spring and fall, when temperatures are between 45 and 75 F, are the best times to grow them. Popular lettuce types include:

  • Loose-leaf varieties — Fast-growing delicate leaves that grow from a central stalk; cutting the outer leaves rather than pulling the whole head will allow the plant to keep growing new leaves to replace what you harvested
  • Butterhead (Boston) — Soft, tender leaves with white heart; requires cool weather and optimal soil quality to thrive
  • Mesclun blends — Spicier greens such as radicchio and mustard add flavor and color to your salads
  • Romaine — Heat-tolerant with crunchy long leaves. Use red or red-speckled varieties to add color to your meal
  • Crisphead (iceberg) — Heat-hardy with thick, crunchy leaves, high in fiber but low in overall nutrition

When and What to Plant for Spring

First, check your Farmer's Almanac (The Old Farmer's Almanac is now available online1) to find the last frost date for your local area. Lettuce should be sown six weeks before the last frost date. Ideal soil temperature is between 55 and 75 F. Within this range, seeds will sprout in two to eight days.

If your seeds resist sprouting, they're probably too old. Lettuce seed should be replaced annually. Fresh seeds have a germination rate of about 80 percent, and a single standard seed packet will produce about 80 heads of lettuce.

Make sure your soil is rich in humus and retains moisture well, as the soil should never be allowed to dry out. Lettuce also needs plenty of nitrogen.  To ensure a continuous spring crop, plant your lettuce as follows:2,3,4

1. Plant seeds in cold frames six weeks before your last spring frost date.

2. At the same time, start another batch of seeds indoors under growing lights. When the seedlings are three weeks old, place them outside for two to three days to adjust before transplanting them into your planting bed.

For the first few days, use a shade cover to protect the tender plants from excessive sun and wind exposure. Reducing watering and exposing the seedlings to lower temperatures for three days before transplanting them into your garden will toughen them up further.

3. Two weeks before your last spring frost date, direct seed another batch in your garden. If the weather threatens to warm up considerably, be sure to use more heat-tolerant varieties.

Be mindful of the fact that if the soil is too warm, germination may not occur. You can encourage germination by placing the seeds on wet blotting paper and refrigerating them for five days before planting them.

4. As the seedlings begin to grow, you'll need to thin the lettuce to allow adequate growing room. Begin thinning when the seedlings have four leaves.

Thin leaf lettuce so the plants are 4 to 6 inches apart; butterheads, 3 to 5 inches; romaine varieties need about 10 to 12 inches; and head lettuce needs about 12 to 16 inches. Rows should be about 18 inches apart.

5. Water daily. The soil must not be allowed to dry out as this will make the leaves thin and bitter. Lettuce has shallow roots, so the soil surface should be kept moist but not soggy. Adding a thick layer of mulch will help retain water and cool the soil. If the weather gets too hot, put up a shade cover.

Fall Crop Growing Tips

For a fall crop, find the date of your first fall frost and start planting seeds eight weeks before the frost date. Direct seed batches every one to two weeks for a continuous fall crop. Once you're a month out from your first frost date, be sure to sow only cold-tolerant varieties such as the following.5

Alternatively, use a mixed seed packet, which can contain a dozen or more varieties. The hardiest ones will survive.

Green Forest

Hyper Red Wave

Merlot

Midnight Ruffles

New Red Fire

Oscarde

Panisse

Pablo

Red Salad Bowl

Salad Bowl

Winter Marvel (Bibb variety)

Winter Wonderland (Romaine)

Planting and Harvesting Tips

If you're using a planting bed, loosen the top 10 inches of soil and mix in about an inch's worth of compost. Seeds should be planted at a depth of about one-fourth inch, with 1 inch between seeds.

If you want, you may simply scatter the seed across your planting bed, but be sure to thin and transplant the seedlings as they start to pop up.

Lettuce can also be grown in containers, or you can add them to your flower beds as edible greenery. Growing several different varieties and planting a new batch every week or two will provide you with fresh salad greens for several months out of the year.

Adding compost or fish emulsion once or twice during growing season will promote speedy growth. If the soil is too dry, the plants can start seeding early, at which point they tend to get really bitter. Pull and discard any plant that goes to seed.

If you want to save seeds, save only those from the very last plants that go to seed, as early seeding is an undesirable trait. To prevent the seed head from toppling over, you may need to stake the plant. Once the seed pods are plump, gather them and store in a paper bag in a cool, dry place.

Harvesting is simple: If you need the whole head, simply cut the head off near the soil line. Alternatively, just cut some of the mature leaves from the outside with a pair of scissors, leaving the center in place. New leaves will continue to fill in.

The best time to harvest is in the morning, after they've had time to plump up with water overnight. Rinse with cool water and pat dry before storing in the refrigerator.

Harvesting your lettuce while still immature is a simple way to get more nutrition out of your lettuce. After about two to three weeks, when the plants have reached a height of about 2 inches, they're considered microgreens. At a height of about 4 inches, they're known as "baby greens."

Both microgreens and baby greens are packed with higher densities of nutrients than full-grown vegetables.

Addressing Pests Without Chemicals

Common pests and ways to address them without toxic pesticides are as follows:

Slugs — Signs of a slug problem include smooth-edged holes in the outer leaves. Simple remedies include collecting them by hand (use gloves), trapping them in beer traps, or spraying cold coffee on infested plants until you see no further sign of infestation. When these approaches fail, I have had great success with Monterey Sluggo, which is OMRI certified for organic gardens.

Aphids — Aphids are typically found in the folds between leaves. Simply spraying them off with cool water can help. Ladybugs and syrphid fly larvae6 (also known as hover flies or flower flies; often mistaken for bees and wasps) are natural predators that can quickly suppress an aphids infestation.

You can tell you have active syrphid fly populations in your garden if you see black oily smears on plant foliage. This is the excrement of the larvae. If you don't have an active syrphid fly population, you can buy live ladybugs (available online) and apply them to your garden.7

Before releasing them, refrigerate the live ladybugs for 30 minutes. It's best to release them in the evening, so be sure to time it properly. Spray some water on the lower portion of the area infected with aphids, then sprinkle the chilled ladybugs on the lower half of the plant. The chilling will slow the ladybug's metabolism, basically putting them to sleep for the night.

As the sun warms them up in the morning, they'll start scavenging for food and laying eggs. So, even though many will fly away, the eggs will hatch larvae that continue feeding on the aphids, and the grown ladybugs will continue the lifecycle of laying eggs and controlling pests in your garden.

Cutworms (moth larvae)8You will typically see these caterpillars in your garden in the evening, after dusk, which is when they start to feed. During daylight hours, they can be hard to find as they curl up in different hiding spots. Cutworms can do severe damage, as they chew through the plant's stem at the very base of the plant. They also feed on plant roots. Usually, infested plants cannot be salvaged.

To prevent cutworms, place a 4-inch-tall plant collar made from cardboard around each plant stem. Save and reuse toilet paper tubes for this purpose. Simply cut the tube in half, lengthwise, and down the center to slip it around the plant. Another alternative is to pick off the cutworms by hand. Go out after dark and use a flashlight to find them.

Place the cutworms in a bucket of soapy water. Repeat every few nights until the infestation is under control. Other chemical-free treatment alternatives include the following:

Sprinkle used coffee grounds or ground up egg shells around your plants

Sprinkle diatomaceous earth around each plant

Use oak leaves as mulch around the plants

Plant tansy near cabbages to ward off cutworms

Fireflies are a natural predator to cutworms, so if you have them in your garden, consider yourself lucky

Preventing Plant Disease

While lettuce needs moist soil, poor drainage can lead to soggy soil that promotes bottom rot and gray mold. As a general guide, only plant lettuce in the same spot once every three years. This will prevent many soilborne diseases. To avoid bottom rot, make sure the soil is moist but well drained. Planting your lettuce on ridges elevated about 4 inches can be helpful.

Also avoid wetting the leaves when watering. Gently fold the leaves off to the side with one hand and only water the soil. Gray mold produces grayish-green or dark brown spots on the leaves. Any infected plants should be pulled and discarded far from your garden to avoid spreading.

Regrow Romaine Lettuce in a Bowl of Water

As seen in the video above, regrowing romaine lettuce requires nothing more than a shallow bowl and some water. Once you've cut off the leaves, leaving a couple of inches' worth of the head, simply place it in a bowl with one-half inch of water. Replace the water daily. New leaves will begin to sprout from the center, eventually regrowing the entire plant.

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