INTRODUCTION
When a plant in the ground or in a pot begins to look pale and unhealthy, or starts to show signs of yellowing, reddening or browning leaves, it is probably experiencing some kind of problem. The exception to this is when a change is due to a normal part of the plant’s cycle, e.g. iris foliage dieback; or leaf color changes in deciduous trees in autumn. Problems may be due to a number of factors — disease, drought, insects or environmental pollution. In order to treat the problem, it is important first to diagnose it.
Solving the problem may be fairly simple if it is diagnosed correctly. When a plant, shows symptoms, check first to see if a disease organism is present. When an insect causes a plant problem, the insects themselves (or their eggs or other signs) are often visible. If a fungus causes plant disease, there are generally signs such as the fuzzy threads (hyphae) that they produce or other clear indications that can be traced. Getting rid of these organisms or restoring good growing conditions may be the answer. Environmental changes may cause plant problems that are similar to nutrient deficiencies or plant disease. Determine whether the plant is getting enough or too much sun; whether it is receiving correct moisture; and whether the temperatures are acceptable for its growth. A shade-loving plant will get burned in full sun, and a plant designed for full sun will not thrive with limited light. Likewise, when a plant is suffering from a deficiency in one essential nutrient or another, there are usually consistent telltale indications unique for each nutrient, but these may appear much like symptoms of pests or environmental conditions.
Nutrient deficiencies are often related to other problems.
- Is the plant getting enough water? Too much? Check the soil moisture, and make sure that there is sufficient drainage. Improper watering, too much or too little, can prevent the plant from obtaining nutrients.
- Is the soil too acid or too alkaline? Nutrients are more or less available in acidic or alkaline soils.
- This is measured as pH, on a scale of 1 (very acid, e.g. concentrated sulfuric acid) to14 (very alkaline e.g. lye). Neutral pH is 7.
- Many plants grow best in a pH range of 5.5 – 7.5
- Soils in the desert tend to have quite a high pH, 8.5 or higher, which inhibits normal plant growth. Soils in areas that receive much rain are usually quite acidic.
- Iron, manganese and zinc are three essential elements that become inaccessible above pH 7.8, hence deficiency of one of these minerals is common in the desert.
- Is the soil very cool?
- Certain nutrients are inaccessible when soils are cool, but the definition of “too cool”varies with the plant. For instance, a cactus will have difficulty taking up nutrients from soils at a temperature that might be perfectly fine for a pine.
Definitions:
- Rosetting: The stem of the plant does not extend normally, so that the youngest leaves grow as a tight bunch near the base of the plant on the ground..
- Bronzing: Leaves develop a shiny purplish tinge overall.
- Stunting: Growing points do not extend normally. The plant is abnormally small and compact.
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