Chlorosis
DiseasesA condition in which leaves produce insufficient chlorophyll, resulting in yellowing of leaf tissue while veins may remain green, often caused by nutrient deficiency or high soil pH.
Chlorosis is the yellowing of leaf tissue due to inadequate chlorophyll production. The most characteristic pattern is interveinal chlorosis, where leaf tissue between the veins turns yellow or pale green while the veins themselves remain darker green. This pattern is commonly seen in iron or manganese deficiency, which is often induced by alkaline soil conditions that make these micronutrients unavailable to roots.
Iron chlorosis is particularly common in species like pin oak, river birch, and red maple when planted in high-pH (alkaline) soils. These species are adapted to acidic soils and cannot efficiently absorb iron when soil pH exceeds about 7.0. The problem is not that iron is absent from the soil but that it is chemically locked up in forms the roots cannot absorb. This is why simply adding iron to alkaline soil often fails to resolve the problem.
Effective management of chlorosis depends on the cause. For pH-induced iron chlorosis, acidifying the soil with eleite sulfur or acidic mulches can help over time. Trunk injection of iron compounds provides faster but temporary relief for symptomatic trees. Long-term solutions include selecting species adapted to the local soil pH and amending planting areas with organic matter to improve nutrient availability. Chlorosis can also result from root damage, compaction, over-watering, and various diseases, so accurate diagnosis is essential.