Leaf necrosis—often referred to as leaf scorch, sunscald, or even "leaf burn"—is a common problem that affects both outdoor and indoor plants. Especially here in our Miami headquarters where the sun is extreme, leaf burn can happen in a matter of minutes if not careful. We'll explore what necrosis in leaves is, dive into the differences between fertilizer burn and sunburn, see how it manifests in popular houseplants, and discuss practical steps to prevent it.

What Is Leaf Necrosis?

Leaf necrosis is the death of leaf tissue, typically visible as brown, dry, or crispy patches on the leaf surface. While the term "necrosis" might sound severe, early signs such as browning or spotting are your plant’s way of signaling that something isn’t quite right. Depending on the cause, necrosis might be limited to the edges or tips of the leaves or appear as scattered spots across the foliage.

Other Names for Leaf Necrosis

• Leaf Scorch: Often used when damage is caused by excessive sun exposure or heat.
• Sunscald: Specifically refers to damage from direct, intense sunlight.
• Leaf Burn: A more general term that can refer to both sun damage and chemical burns (such as fertilizer burn).

What Causes Leaf Necrosis?

The primary culprits behind necrosis are environmental stresses—particularly improper light exposure and over-fertilization. Although both can result in similar symptoms, the underlying causes and preventative measures differ.

Sunburn

• Cause: Excessive exposure to intense, direct sunlight, especially during peak hours, can overheat the leaf tissues. This is more common when plants are suddenly moved from a low-light to a high-light environment without proper acclimation.
• Symptoms: Brown or bleached patches, often on the side of the leaf that faces the sun. Crispy or dried edges.
• Temperature & Light Metrics: While it varies by plant, many houseplants can suffer when exposed to temperatures above 85°F (29°C) coupled with intense direct light. Light levels exceeding several thousand lux (especially if measured in environments where indirect light is typical) can contribute to sunscald.

Fertilizer Burn

• Cause: Over-fertilization leads to salt buildup in the soil or growing medium. These salts draw moisture out of the leaves and roots, causing the tissue to dry out and die.
• Symptoms: Brown, crispy tips or edges that often appear uniformly. A more “burned” look rather than patchy discoloration.
• Differences from Sunburn: Fertilizer burn tends to affect the leaf edges or tips in a more uniform way, while sunburn usually results in uneven, patchy damage. Unlike sunburn, fertilizer burn is not related to temperature or light but to the chemical concentration in the soil.

How Necrosis Looks in Different Plants

Different species show necrosis in unique ways due to their leaf structure, thickness, and overall tolerance:

Money Tree (Pachira aquatica)

Appearance: Money trees have broad, palmate leaves. In cases of necrosis, you might see whitening and crisping from the center of the leaf or leaf tips.

Sensitivity: They prefer bright, indirect light. Direct, intense sunlight or over-fertilizing can quickly lead to scorch marks.

Peace Lily (Spathiphyllum)

Appearance: Peace lilies typically feature glossy, dark green leaves with occasional white blooms.

Sensitivity: These plants thrive in low to moderate light; excessive direct sunlight can cause unsightly brown spots or patches, while too much fertilizer might lead to crisped edges.

Pothos (Epipremnum aureum)

Appearance: With its variegated leaves, pothos can show brown patches or streaks if stressed.

Sensitivity: Pothos are generally resilient but can develop necrosis if exposed to too much direct light or if over-fertilized, making their variegation appear burnt and debossed.

Begonia

Appearance: Begonias come in various leaf shapes and colors. Necrosis may appear as uneven browning or faded areas almost like a blended watercolor, particularly on leaves that receive too much direct sunlight. In Maculatas, the necrosis will look pinkish, as if the red pigment from the underside of the leaves have started to bleed throughout the leaf.

Sensitivity: They often prefer indirect light, and direct sun exposure can lead to dramatic leaf burn.

How to Prevent Leaf Necrosis

1. Gradual Light Acclimation

For Sunburn: If you need to move a plant from low light to higher light, do it gradually. Start with indirect sunlight and slowly increase the exposure over a couple of weeks.

Tip: Use sheer curtains or place the plant in a shaded area before moving it to full sun.

2. Providing Man-Made Shade

For Sunburn: If moving your plant is not possible, use a shade cloth for peak afternoon sun hours or on extremely sunny days. You can find shade cloth on most shopping sites or retailers. 

Tip: Be sure to use darker shade cloth that looks like netting or has a lot of holes for air to flow rather than tinted plastic coverings or enclosures which can further suffocate the plant. 

3. Proper Fertilization

For Fertilizer Burn: Always follow the recommended dilution rates. Consider using slow-release fertilizers to avoid a sudden spike in salt concentration.

Tip: If signs of fertilizer burn appear, flush the soil with water to help remove excess salts.

4. Monitor Environmental Conditions

Temperature: Keep an eye on ambient temperatures, especially during peak summer hours. Aim to keep indoor temperatures below 85°F (29°C) if your plants are in direct or near-direct sunlight.

Light Metrics: Use a light meter if possible. Many houseplants thrive in environments with moderate lux levels. For instance, a range of 1,000 to 3,000 lux is often ideal for indoor foliage plants, while direct sunlight can easily exceed 10,000 lux.

5. Regular Maintenance

Inspection: Regularly inspect your plants for early signs of stress. Quick intervention can prevent minor issues from becoming severe necrosis.

Cleaning: Remove dead or damaged foliage to encourage healthy new growth and reduce stress on the plant.

Conclusion

Necrosis in leaves is a visible indicator that your plant is experiencing environmental stress—whether it’s due to too much direct sunlight (sun scorch) or an excess of fertilizer (fertilizer burn). By understanding the specific needs of your plants—be it a money tree, peace lily, pothos, or begonia—you can tailor your care to prevent these issues. Gradual acclimation to light, careful fertilization, and monitoring of temperature and light levels are key to maintaining healthy, vibrant foliage. Remember, early detection and proactive care can save your plants from the damaging effects of necrosis.

Happy gardening, and may your leaves stay lush and healthy!