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Reasons for Yellow Lettuce
Don't let yellowing lettuce leaves ruin your salad. Protect your lettuce crop by avoiding common cultural problems that result in wilting or yellowing.
Grow your own salad at home with a backyard patch of lettuce (Lactuca sativa), which thrives throughout U.S. Department of Agriculture plant hardiness zones 4 through 9. Since this vegetable is prized for its crisp, edible leaves, yellowing foliage can ruin your dreams of a homemade salad harvest. Lettuce may turn yellow for a few common reasons, each which has an organic, natural solution.
Not Enough Water
The lettuce plant has a very shallow root system, which makes it especially prone to drought stress. The plant requires consistently moist soil conditions at all times, without which it will wilt, turn yellow and eventually lose all of its leaves.
When watering lettuce, use enough irrigation to moisten the soil to a depth of 6 inches. Water the lettuce bed again as soon as the top inch of soil has dried out.
Tip
Water lettuce in the early morning to give it the crucial moisture it needs to get through the hottest portion of the day.
Extreme Soil Temperature Fluctuations
Since lettuce roots lie so close to the soil surface, the plant is more prone to temperature-induced stress that can result in wilting and yellowing of the lettuce leaves. Mulch creates a protective barrier on the soil surface that helps to shield the soil from the sun and keeps temperatures constant and cool.
Spread 2 to 3 inches of organic mulch around the lettuce plants. Example mulching materials include:
Shredded leaves
Weed-free straw or hay
Fine bark chips
Compost
Additionally, mulch helps prevent weed growth and also conserves soil moisture, further enhancing the lettuce plant's health and appearance.
Poor Soil Nutrient Levels
As lettuce grows, it needs rich levels of soil nutrients to support optimal foliage development. Nutrient-depleted soil may result in lettuce plants that appear stunted with leaves that aren't fully developed or that have a pale, yellow-green hue. When given the right amount of fertilizer, lettuce leaves turn a dark green.
Before planting lettuce, set a nutritional foundation by spreading 1 1/2 pounds of 5-10-10 fertilizer for every 50 square feet of gardening space. A couple months after the lettuce has been planted, fertilize the garden again with 1/2 pound of 33-0-0 fertilizer for every 50 feet of lettuce row.
Pest Invasions
You are not the only thing that enjoys the taste of lettuce. Occasionally, lettuce beds may get attacked by a variety of soft-bodied pests, including aphids, leafhoppers and whiteflies. Left uncontrolled, pest infestations can reach such heavy numbers that they cause wilting, yellowing or loss of leaves. Some pests, such as the leafhopper, spread a disease called yellows disease that, true to its name, causes yellow leaves.
Dust lettuce plants with food-grade diatomaceous earth to protect it from leafhoppers and other leaf-eating pests. Repeat the diatomaceous earth application after any rainy days.
Alternatively, spray lettuce plants with a strong blast of water from a garden hose. This is often enough to dislodge and kill common pests like aphids and whiteflies, and regular spraying keeps pest populations at levels too low to cause a problem.
If all else fails, make your own homemade insecticide soap spray to kill aphids, leafhoppers and other soft-bodied pests.
Things You'll Need
Blender
Garlic bulb
Onion
Powdered cayenne pepper
Measuring cups
Cheesecloth
Liquid dish soap
Spray bottle
Step 1
Place an entire garlic bulb and a small onion into a blender and blend on medium until a fine pulp is created.
Step 2
Add 1 teaspoon of powdered, dehydrated cayenne pepper.
Step 3
Add 1 quart of water.
Step 4
Mix thoroughly and allow to steep of an hour, but preferably overnight.
Step 5
Pour the liquid through a piece of cheesecloth into a plastic spray bottle.
Step 6
Add 1 tablespoon of liquid dish soap.
Step 7
Spray the soapy solution on affected lettuce plants. Coat all exposed surfaces of the plant, including the undersides of leaves where aphids and other pests tend to congregate.
Step 8
Repeat once a week until pest activity subsides.
Tip
If you're worried about adding unnecessary chemicals to your lettuce garden, consider using liquid dish soap that's labeled as eco-friendly and biodegradable.
Warning
Rinse the lettuce plants with fresh water a couple of hours after spraying them.
