Leaf Scorch: How to Rescue Sunburned Garden Plants

Living in Phoenix Arizona, aka the valley of the sun, we gardeners never have a problem with our plants being sunlight deficient.  In fact, our dilemma is quite the opposite. 

Our hot desert sun can be extremely intense, especially during the summer months.  Since sun damage can mimic other plant deficiencies it can sometimes be difficult to determine if that’s the problem. 

Can too much Sun Kill Plants? 

The short answer is yes it can.  Typically, a plant or tree isn’t going to be immediately killed when receiving too much sun, but, it will be a gradual process over a few days or weeks. 

A lot of times there are identifiable symptoms of sun stress that can help a gardener prevent death.  According to Science Mag, plants naturally desire sunlight, but excessive sunlight can create potentially deadly free radicals. 

Plants recover energy from the sun with the help of chlorophyll and carotenoid, two photon-capturing molecules. But if the plants are exposed to too much sun, these molecules engross more energy than they can handle and create reactive species of oxygen that can destroy the plant. 

Acclimating Indoor Plants or Seedlings to Sun

When bringing seedlings or indoor plants outdoors, it’s always a good idea to help them get acclimated to the intense sun, by hardening off process. Plants that have grown in a sheltered or indoor setting aren’t used to the outdoor conditions and increased sunlight. 

Without the hardening off process, it’s quite common for sun scorch to occur a day or two after placing indoor plants out in the sun.  Hardening plants off is a process that can take up to a couple of weeks.  This can be done by gradually introducing the plant to sun and outdoor conditions. 

Typically you start by placing the plant or seedling in full shade for a couple of hours, then working your way up to full sun.  Here is a schedule to follow:

1. Full shade for 3 hours and increase the duration of time over the next 3 days by 1 hour
2. On Day 4, start placing the plants in a spot where they get morning sun for a couple of hours, followed by shade the rest of the day. Follow this routine for the next 2-3 days.  Bring in at night.
3. On day 7, plants should be able to handle full sun and being outside overnight.

*Make sure plants are thoroughly watered each day before going outdoors.

How to Recognize Stress from Sunlight

It’s important to be able to identify some of the symptoms of sun stress in order to save the plant from potential problems or death.  Here are some common signs of sunburn in plants:

• Leaves begin to have a bleached appearance where the green color turns very light green, white or greyish.
• New growth begins to wilt
• Brown, dry spots on leaves
• Discoloration of the leaf veins
• Dry dead leaves
• Stunted growth
• Wilting

Not only can sun be an issue for the leaves of the tree, but also the trunk and branches.  On young trees, the branches and trunks that are exposed to full sun can be damaged by sunscald. 

This is highly problematic for citrus in our area.  Avoid pruning foliage that shades and protects tender new branches and sensitive tree trunks.  Once the tree has been damaged by sunscald there is nothing that can be done to fix it. 

Often times the trunk will crack or look black in damaged areas. These cracks can make the tree more susceptible to diseases or pests. Your best bet is to take preventative measures early on because a healthy tree is apt to handle the elements better.

How to Save Sunburned Garden Plants

Once the leaves have already been scorched or damaged, there’s nothing more you can do about the impacted leaves.  Just allow them to drop on their own.  As previously mentioned limbs and trunks that have been damaged by the sun will remain that way.  The tree can still remain vigorous and healthy if it’s still living. 

Shade

Adding a shade cloth is one of the best ways to help get your tree or plant through the extreme sun.  I utilize shade cloth the first year or two when planting more sensitive fruit trees here in the desert. 

This helps the trees to get established in our climate which helps them to withstand the conditions as they age.  Your first reaction when noticing sun stress may be to completely shade the plant out, but this can have adverse effects as well.  Plants and trees need some sun to photosynthesize and grow. 

It’s also hard on the plant when you remove the full shade back into full sun.  Utilizing a shade cloth at the right percentage will allow for some sun with shade.  Check out my post here: When to Use a Shade Cloth in the Garden, to help you decide the best shade cloth for your needs.

Paint

For trunks and branches that are exposed, using white paint can help reflect the sun rays.  Be careful not to use oil-based paint, which can be harmful to the trunk.  There are some drawbacks to using paint, for instance, it doesn’t look good and it makes it hard to distinguish if you have other problems with the trunk like borers or diseases. 

If you’re going to use paint, I highly recommend, IV Organics, click here for pricing options on Amazon.  It has natural based products which can be beneficial for your trees. 

Health

Make sure that your plant is properly hydrated.  Lay a thick layer of mulch down to help keep the roots cooler.  Moistening the mulch every morning can help raise the humidity. Prune any dead, diseased, or crossing branches. 

Ensure that your tree or plant is being fed consistently with things like compost and organic fertilizers.  Here are my recommended products.  A healthy plant can recover quickly, just like a healthy human is more resistant to problems. 

Get them Established when Young

You’ll be able to minimize a lot of the effects of sun damage when you help young trees or plants through those challenging hot days.  There are many trees and plants that are more drought tolerant or are able to handle even being in full desert sun. 

If you have a basic understanding of your plants you’ll know what they’re able to handle.  Many times when you buy a plant from a store it will tell you how much sun the plant needs.  In a hot, dry climate those recommendations aren’t always accurate. 

Planting sun sensitive plants in an area where they get some afternoon summer shade will help them to build root establishment when young.  Utilizing things like shade screens and mulch also will get your young plant off to a good start.  Once the tree or plant has a solid foundation, it’ll be able to push through that intense sun with more vigor. 

RELATED POST: How to Water Fruit Trees in Hot Climates the Right Way

Final Thoughts

For those of us gardening in hot, dry regions of the world, knowing how to handle intense sunlight is a key to a successful garden.  As you gain an understanding of signs and symptoms, you’ll be proactive with aiding your plants through those intense summer days. 

Also, as your knowledge of what your plants can handle increases, when it comes to sun exposure it will help get them established when they’re young for a productive future.