Tomato seedlings can suffer from sunscald when they are planted from a greenhouse into direct sunlight. Tomato seedlings can recover from this problem with a few simple steps. If more than 50% of the leaves and stems are still green, water the plant well and add a dilute liquid nitrogen fertilizer.
This will give your tomato seedlings the best chance of recovering from sunscald. If you notice white leaf patches on the edges of the leaves, particularly the new ones your plant might be suffering from sunscald.
This article will explore what to look out for to work out if your plant has sunscald and what you can do to help your tomato plant to recover.
Will tomato seedlings recover from sunscald?
For tomato seedlings that have been affected by sunscald there are some things to look out for to know whether or not they will recover. Tomato seedlings are fairly hardy once they have more than one set of leaves so here is what you can look out for to know.
Tomato seedlings will recover from sunscald if:
- If more than 50% of the leaves are still green
- If the stems are still green
- If the weather has become mild
- You have treated them with water and seaweed solution
Tomato plants that have any of the signs above are likely to recover from sunscald. For plants where their leaves have turned white just on the edges, they can recover quickly.
Tomato sunscald often affects the early, young leaves or the tips of leaves most exposed to the sun. This is because most tomato seedlings would have been grown in greenhouses and will not be used to direct sunlight.
How to treat sunscald on tomato seedlings for recovery
Here are my tips to preventing sunscald on tomato seedlings at home and help them to thrive when you plant them out from a nursery.
1. Water them well with dilute seaweed solution
The first step to help your tomato seedlings recover from sunscald is to water them well with added seaweed solution. This will help to strengthen their roots and improve the soil.
2. Do not remove damaged leaves
It might seem like a good idea to remove damaged leaves from the tomato plants but instead it is best to leave them on for now. These leaves will still photosynthesize and provide the plant with food. Once the tomato seedling has recovered and grown new leaves the old damaged leaves can be pinched off.
3. Surround with mulch
Surrounding tomatoes with mulch is another important step to help them recover from sunscald. It will help to keep the soil moist for longer and to reduce the radiant heat that will come up from the soil.
Straw or sugar cane mulch is the perfect choice for tomato seedlings but you can also use fine bark mulch if you have it. Compost will also work well as a much but works best if you layer straw on top.
4. Feed tomato seedlings with liquid fertilizer
The final step to help a tomato seedling to recover from sunscald is to give it a feed with liquid nitrogen fertilizer. I like to use fish emulsion but a liquid fertilizer designed for vegetables will also work well.
Add a dilute mix every 2 weeks around 3x until you see the plant start to recover. A dilute mix will give the plant a quick nitrogen boost which will help it to grow new leaves quickly.
How to prevent sunscald on tomato seedlings
Sunscald can be prevent on new tomato seedlings through the process of hardening off. This is where the tomato seedling is gradually exposed to the sunlight rather than being planted out directly into full sun.
To harden off tomato seedlings bring them out into the direct early morning sun for around 2 hours to begin with. Gradually increase their time in the sun for the first 2 weeks. If this is done in Spring they will adjust to the sunlight and be ready to plant out.
In mild weather and sunlight that is not as harsh, the process of hardening off can be quicker. I have planted my tomato seedlings out directly into garden beds because they get afternoon shade.
I also like to plant my tomato seedlings out in early Spring because it means they will not have such a big shock when the weather heats up in summer.
Cover with mulch
Mulch is important to prevent sunscald in newly planted tomatoes. The soil can heat up quickly direct sun and the heat can reflect up to the leaves of the tomato. This reflected heat can be decreased by adding straw or sugar cane mulch underneath. This will also help to keep water in the soil for longer.
Nutrients & Water
Boost with a dilute solution of nitrogen based fertilizer. I like fish emulsion but you can also use another organic fertilizer made for vegetables. I like to add pelleted chicken manure around the base of the plant when I first plant it out this will give it a longer lasting feed of nitrogen.
Seaweed solution is easily added to your watering can and can be given to your tomatoes monthly to help to strengthen their root system. A healthy tomato plant with a strong root system will be more resistant to heat stress and sunscald.
Will tomato seedlings recover from sunscald? | Summary
Tomato seedlings can recover from sunscald if you catch it early and treat them quickly. Water is the key to help them recover quickly along with mulch and fertilizer. For those very hot regions, layering a piece of shade cloth over the top of the plants might be necessary to stop them burning.
A mature tomato plant will be more resistant to sun damage but the fruit itself can get burnt. In extreme weather, draping shade cloth over the top of the plant might be what saves the leaves and fruit from burn.
Do not give up on tomato seedling that has suffered from scald because it can recover well.