Lettuce leaves will turn yellow if the soil is lacking in nitrogen, if they are being overwatered, attacked by pests or if they are not getting enough sunlight. Overwatering will wash nitrogen out of the soil and can cause root rot. Both will stop the lettuce getting the nutrients it needs and developing the green chlorophyll in its leaves.
Check the leaves carefully for aphids or scale and treat them with neem oil. Yellow leaves on lettuces can be easily fixed and this article will explore what to do to save your plants.
- Lettuce leaves will turn yellow if they are not getting enough sunlight.
- Improve the soil with aged cow manure and pelleted chicken manure to add nitrogen and prevent yellow leaves.
- Interplant lettuce leaves with other flowers and vegetables to deter pests.
- Give yellow lettuces a dose of liquid nitrogen fertilizer to help them to turn green fast.
- Pinch off yellow leaves to make room for new green ones.
Top causes of leaves turning yellow on lettuces
Here are the top reasons why lettuce leaves turn yellow. Check out each one and see if this might be the cause of the problem for your plants.
1. Lack of nitrogen
Lettuce plants are not getting enough nitrogen will start to develop yellow leaves. Overwatering plants can wash water soluble nitrogen out of the soil.
Lettuces need loads of nitrogen to help them to develop the green chlorophyll in their leaves.
Improving the soil before planting lettuce will help to prevent yellow leaves. Dig through aged compost and 1-2 handfuls of pelleted chicken manure. This will add loads of organic matter and nitrogen to feed the leaves.
If your lettuces are already growing in the ground, sprinkle pelleted chicken manure or an all-purpose nitrogen fertilizer around the plants and water it in.
For a quick dose of nitrogen, give the plants a liquid nitrogen fertilizer. This will be absorbed quickly and will last for around 2 weeks. Follow this up with a handful of pelleted chicken manure to feed the plants for the next 2-3 months.
2. Lack of water
Lettuces that are not getting enough water can develop yellow leaves. Lettuces grown in poor, sandy soil can dry out quickly.
Very hot weather can dry out lettuce quickly. Water them in the morning before a hot day. Consistent water will help to prevent yellowing leaves on lettuces over spring and summer.
Mix compost through the soil if it is overly sandy or the water drains out too fast. Surround lettuce with straw mulch to help water to stay in the soil for longer.
Check out this video for some easy ways to save yellowing plants.
3. Lack of sun
Lettuces will grow best in at least 6 hours of sunlight. Plants that are getting less than that can start to turn light green and then yellow. Lettuce needs sunlight with nitrogen to develop green chlorophyll in their leaves. The less light they get the less green the leaves will be.
Move potted lettuce into a sunny spot if you can find one. Find the sunniest spot you can when planting new lettuce seeds or seedlings.
Overwatering can cause lettuce leaves to turn yellow. Overwatering will wash nitrogen out of the soil and away from the roots. Nitrogen is essential for lettuce leaves and to prevent leaf yellowing.
Before watering lettuces check the soil first to see if it is dry 1-2 inches down. Water only when the top soil has started to dry out to avoid overwatering.
I find in summer that I need to water my lettuce every 2 days. I like to water in the morning so that any water on the leaves will quickly dry out to avoid fungal growth.
5. Pest attack
Pest attack can cause lettuce leaves to turn yellow. Sap sucking insects such as scale or aphids sucking out the nutrients and water and causing damage to the leaf. The leaf will eventually turn yellow.
Both of these insects can be treated with Eco or Neem oil. Spray the bugs off with a strong jet of water if there are only a few.
Wait until the plant has dried and then spray it with dilute neem oil. Do this in the morning to avoid burning the leaves.
How to save lettuce with yellow leaves
Here are 3 easy steps to save lettuce with yellow leaves. This will help the plants to grow new green leaves to replace yellow ones.
1. Check the soil moisture content and water it well
Stick your finger 1-2 inches below the surface of the soil to check the moisture level. If the soil is dry then water it deeply every second day for a week. Surround the plant with mulch to help to keep water in the soil for longer.
2. Give lettuce liquid nitrogen fertilizer
Add liquid nitrogen fertilizer to the lettuce plant to replace lost nitrogen. Wait for 2 weeks and then give it a feed of pelleted chicken manure and water it in well.
3. Pinch off yellow and brown leaves
Once you have taken these steps pinch off any remaining yellow or brown leaves. Lettuce will grow new healthy green leaves from the center to replace old leaves.
Lettuce Leaves Turning Yellow | Summary
Yellow leaves on lettuce plants are usually caused by can be trimmed off to tidy up the plant once you work out what is causing the problem. Lettuces are hardy and will recover once they are given the nutrients and water they need.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.