Leaf Burn - The Causes and How to Fix It

Leaf burn, also known as leaf scorch or sun scald, is when the leaves on your plants are dehydrated and the sun causes them to discolor and form brown crunchy spots. The plant dehydration can be caused by: 

• Underwatering

• Too much heat in the room or nearby

• Roots that cannot soak up enough water

• A health issue with the plant causing it to not distribute water efficiently

• Incorrect placement where the houseplants get too much direct sunlight or have reflective surfaces scorching leaves

No plant is immune to leaf burn, even light-loving ones like Desert Cactus, Grass, and Palm Trees. Plants with large, broad leaves like Monstera and Alocasia (Elephant Ear Plants) are more susceptible to leaf burn due to the larger surface area that is hit by the sun, and so are plants that require a lot of moisture like Philodendron and Pothos. 

While some causes of leaf burn like too much sunlight are easy to fix, others can be harder to detect like root girdling. This guide walks you through making sure it is leaf burn, then the causes of leaf scorching, and how to treat it with the cause. 

Brown and crunchy leaves could be leaf burn, dehydration, too much heat, malnutrition, and root rot from overwatering. If the spots are not actually leafburn, you may treat your plant for the incorrect ailment and lose it. 

Here’s some of the common signs of leaf burn so you can feel confident that sun scorch is the issue:

• The brown crunchy spots start at the tips and outer edges, then work their way inwards and up the leaf.

• Leaves curl inward while turning brown and don’t unravel at night which is different than nyctinasty which Calathea (Prayer Plants) do.

• The brown leaves begin falling off prematurely.

• White, yellow, and brown discoloration is happening in between the veins due to a lack of moisture making it through the leaf.

If this is what is happening to your house or garden plants, don’t panic. Leaf burn is easy to treat once you know the cause.

Anything that causes your plant or the leaf to dehydrate and get too much sun can cause leaf burn. This includes decor items in your home that reflect sunlight directly onto the plant’s leaves like a mirror. The condensed light reflection causes a beam that overheats a spot on the leaf causing it to dehydrate and burn creating a sun scorch spot. Here are some of the main causes, and what to do to stop the problem.

Too much direct sunlight dehydrates the plant including the leaves and the potting mix causing it to either not be able to get enough water to distribute, or the leaves to dry out and burn. This is why the placement of the plant and paying attention to the type and amount of sunlight needed is important to prevent scorching. 

Desert Cacti (not tropical like Christmas and Easter Cactus) can handle 10-12 hours of direct sunlight as this is similar to their natural habitat. Moss, Jewel Orchids, and terrarium plants may scorch in less than 2 hours of direct sunlight due to their natural habitats under a forest canopy or in shady areas like the entrance to a cave. 

If direct sunlight is the cause, move your plant away from the source including windows and anything that projects a beam of light like a carved crystal vase, or add sheer curtains to diffuse the light while allowing natural sunlight to fill the space.

Dehydration leads to leaf burn as the plant uses moisture for survival in addition to protecting itself from issues like leafburn. The lack of moisture inside prevents it from being able to protect itself from too much heat and from distributing moisture for processes like photosynthesis where it creates food. This is why proper watering and making sure the potting mix your plant is in has proper moisture levels.

Go to your favorite plant shop (like us) and look at the product pages for your specific type of plant to find watering instructions for your plants. The different species will have different watering needs based on where they come from naturally and their type of root system.

Most tropical houseplants will need watered once the top 1 or 2 inches of potting mix are dry, so a weekly watering can be a good schedule. Others that have rhizomes will need to dry out completely and then be watered, and these may need watered every two to three weeks depending on where you live and where the plant is placed.

Pro-Tip: It is actually better to water when the sun is out as dark and damp conditions encourage mold growth. 

Plants release moisture via sweating, just like us, through a process called transpiration when it is too hot. If your air conditioning breaks, you’re on vacation and your home heats up, or the plant is in a sun room or garden, the heat can drain your plant of moisture. 

If this is the cause of dehydration that is leading to leaf burn, move your potted plants to a less hot room or try increasing the humidity levels and watering schedule to account for the heat dehydration.

Over-fertilization can cause leaf burn as the salts in the fertilizer or plant food settle in the soil making it more hydrophilic (water-loving) than the root system. The end effect is the salts drawing water out of the plant due to osmosis. 

During osmosis the water moves from an area with a high concentration of water (the plant) to an area with a lower water concentration. After over-fertilization, the ratio of salt to water in the soil is higher compared to the ratio of salt to water in the plant (where water will be greater than salt). In order to try to “even” out both sides, water will travel out of the plant into the soil or be retained in the soil until that ratio is fixed leading to dehydration. 

This is the same principle for how salted preserves/dried food is made, by over-fertilizing you are making your houseplant a form of “plant jerky”. To avoid this always follow the guidelines on your fertilizer and don’t add extra in because you think your plants may be a bit hungry. 

Girdling roots (roots that outgrow their pot and spiral around it) can restrict water movement within the plant and cause dehydration which leads to leaf scorch. Check your plants every 1 to 3 years to see if they need a larger pot. This is one of the lesser known causes of leaf burn, but a very common one too.

Pro-tip: If any roots are rotting, damaged, or unhealthy, trim them with disinfected shears before repotting as the issue could spread to healthy roots and kill the plant.

To treat leaf burn, diagnose the issue to make sure it is in fact leaf burn, then find the cause. It could be too much light, water, humidity levels, dehydration, etc… and remove the issue. After making adjustments, monitor for 2-4 weeks to see if the problem resolves. 

If the leaf burn has already created brown and crunchy spots:

1. Disinfect a pair of gardening or pruning shears

2. Cut off the brown crunchy leaves or cut out the section that is scorched.

3. Move the plant to a space where it can no longer be impacted by the lightsource.

To prevent leaf burn, start with how your plant is exposed to sunlight and relocate the plant to a spot with indirect sunlight, or for plants that require direct sunplace place them by a window that does not get the hot afternoon sun. 

Additional steps you can take to prevent leaf burn include:

1.  Remembering to observe and adapt your care routine based on the specific needs of each plant species. 

2. Use plant groupings where the larger, more light-tolerant plants act as shade for those underneath, preventing leaf burn. 

3. Use a properly formulated, well-aerated potting mix that can hold the proper amount of moisture like our Dirt Bag. 

4. Regularly inspect your pots for roots hanging out of the drainage holes or outgrowing their containers, and move them to a larger pot to help their roots remain healthy. 

5. Use only a balanced liquid fertilizer, preferably diluted, only during your plants' growing period to prevent over-fertilizing. 

6. Keep the home humidity at least at typical home conditions of 30-50% and monitor it with a humidifier with a built-in humidistat in the room. 

Leaf burn is one of the easiest plant health issues to treat. It’s a matter of removing the scorched surfaces and fixing the intensity of the light source. If the light source is fine and the issue is dehydration, modify your watering or care routines and if it is roots that have outgrown their container, repot the houseplant.