1、Chemical or Fertiliser Burn

Chemical burn is caused either when chemicals are too concentrate when spraying, fertiliser is added at planting time or spraying was done during the heat of the day. Sprays must be used during cool weather as drops of water held on the leaves act like a magnifying glass and burn the plant.

2、Necrosis: What Does Leaf Scorch Look Like? – Cowbell Plant Co.

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.

3、What's wrong with this rose bush? A lesson in irrigation

A sunburned bush will shed damaged leaves and recover, as long as it has enough water. Foliage burn happens when time-release or other fertilizer is introduced to the soil and there's not enough water for the roots to process it. The plant pulls moisture out of its foliage and sends it to the roots so it can pick up those nutrients.

4、Heat Stress Or Fertilizer Burn

Typically, the browning of Knock Out rose leaves may be the result of too many nutrients. They do thrive in fertile soil, however, over-applying fertilizer may lead to high salinnity content in soil as well as brown leaves.

5、SUN BURN

Commonly found on roses during hot summers. Caused mostly by watering where salt in the water is deposited on the leaves along the edges and the sun evaporates the water leaving the salt which then burns these areas. Solution is to avoid getting too much water on the leaves with watering.

Common Cultural: Fertilizer burn

Excessive use of fertilizers can damage or kill plants. High levels of salts in the soil will damage plant roots, resulting in reduced water uptake. The salts may also accumulate in leaf tissues, causing a dieback or necrosis of leaf tips and margins.

Heat Scorching

Sunburnt stems will not normally affect the plant but can look unsightly. Wait for new watershoots to grow before removal. Ensure you follow the watering guide as this will prevent the majority of damage occuring. Chemical burn is when a spray is too concentrate.

Heat Stress, Water, and Tips to care for roses in heat

Some liquid/water soluble fertilizer like fish fertilizer can be used as a supplement, but once again not too much. I've compiled some articles relating to caring for roses in hot summer months that I found from different sources/referces below: Q: Heat Damage and Heat Tolerance in Roses explained. Q: How to indentify if my roses have heat stress?

Leaf Scorch

This damage may appear as either leaf spots or marginal leaf burns. The damage may show up on one sector of the plant, one limb of a tree or shrub, or the entire plant, depending on how much of the root system is damaged by fertilizer.

Salt burn or Fertiliser Burn

Fertilizer burn occurs when plants absorb too much fertilizer, particularly when the nutrients are too concentrated. This can lead to the scorching of plant roots and foliage, resulting in stunted growth, leaf discoloration, and, in severe cases, plant death.

Fertilizer burn and sunburn are two common plant disorders in roses, differing in appearance, symptoms, transmission methods, and control measures. This article will elaborate on the distinctions between them from the following aspects:

1. Appearance and Symptoms

• Fertilizer Burn on Rose Leaves: Typically characterized by yellowing, scorching, curling, or deformation of leaves. Affected areas may develop water-soaked spots, and severe cases can lead to entire leaves turning yellow and dropping. This disorder is often linked to nutrient excess, such as overuse of nitrogen, potassium, or phosphorus fertilizers, which overstimulate plant growth and weaken resistance.
• Sunburn: Caused by prolonged exposure to intense sunlight or high temperatures, resulting in leaf yellowing, dryness, and symptoms like burnt edges or necrosis. Sunburned leaves usually lack distinct patches but appear lighter in color, brittle, and prone to cracking.

2. Transmission Methods

• Fertilizer Burn: Primarily arises from soil deficiencies in microelements or improper fertilization practices. If fertilization strategies are not adjusted promptly, the condition worsens, harming the entire plant.
• Sunburn: Mainly triggered by environmental factors, such as consecutive hot weather, drought, or intense sunlight. Its progression is relatively slow, but timely intervention is critical once symptoms appear.

3. Control Measures

• Fertilizer Burn: Addressed by revising fertilization plans to avoid excessive nitrogen, potassium, or phosphorus. Proper watering to maintain soil moisture helps reduce nutrient-related damage. For existing burns, foliar spraying with balanced nutrients or microelement supplements can alleviate symptoms.
• Sunburn: Prevented by shielding plants from prolonged sun exposure, especially during heatwaves. Cooling methods like shading or misting can mitigate risks. Damaged tissues should be pruned, and enhanced irrigation promotes recovery.

4. Prevention Strategies

• Fertilizer Burn: Ensure balanced fertilization during cultivation, avoiding overreliance on specific nutrients. Regularly monitor plant health to detect and resolve nutrient imbalances early.
• Sunburn: Before hot seasons, use shade cloths or shelters to protect plants. Opt for drought-resistant or heat-tolerant rose varieties to minimize sunburn risks.

While both fertilizer burn and sunburn affect roses, their causes, symptoms, and management differ significantly. Growing roses requires careful fertilization to prevent nutrient excess and proactive adjustments to environmental stresses. Vigilant observation and timely intervention are key to maintaining plant health and mitigating these disorders.