Plants, whether cultivated or wild, generally grow well when the soil provides them with adequate nutrients and moisture, sufficient light reaches their leaves, and the temperature stays within a “normal” range. However, plants can get sick, most often from a disease-causing agent like a bacteria or fungus. But there are also plant ailments that may look like a disease but in fact are caused by factors other than living (biotic) agents. These are known as abiotic disorders.
Common abiotic disorders include:
- Nutrient deficiencies – when a plant lacks a required material for growth. Example – iron unavailability in the soil resulting in yellowing leaves (chlorosis).
- Nutrient excesses – too much of a given nutrient. Example – burned leaf edges especially during drought periods from overfertilizing with a fast-acting nitrogen fertilizer.
- Herbicide damage – plants that have been exposed to weedkiller. Example: New foliage is cupped, curled, or small leaves as a result of weedkiller spray drift.
- Sunburn – direct or reflected sunlight hitting canes or foliage. Example – blackened areas, especially on the south and west sides of canes.
- Leaf scorch – excessively high temperatures combined with low moisture levels. Example – leaves turn yellow or have brown leaf edges, with a scorched appearance.
- Desiccation – water loss from the leaves and canes due to temperatures, wind, water availability. Example – wilted, drooping leaves, stunted growth.
- Frost damage – exposure to freezing temperatures followed by warming. Example – leaves appear water-soaked, shrivel, and turn dark brown or black, cracks in wood of canes.
Prevention is the key for most of these abiotic conditions. While you can’t control temperatures or wind, you can make sure your plants are adequately watered and fertilized (not too little or too much), keep pets away from the plants, and protect newly planted bareroot roses by surrounding the new plant with mulch until it has developed roots and can withstand drying winds. Keep in mind that any of these conditions can weaken a rose and allow invasion by many secondary fungi and insects.
By Nanette Londeree, Master Rosarian