Chlorosis, or yellowing, refers to plant leaves that are become faded-green or yellowed, rather than a healthy, dark green color. When manifest, the leaf veins often will remain dark while the rest of the leaf becomes lighter. This condition is common with maples, but also presents itself in pin oak, aspen, sweet gum, birch, and various other trees and shrubs.
Idaho soils typically have an alkaline, high pH level, which may cause problems such as nutrient-deficiency chlorosis. In such soil types minor nutrients are often bound within the soil chemistry, making them unattainable by the to the plant roots. The most limiting of the nutrients in a high soil pH system tend to be iron and manganese. Both nutrients present similar symptoms- however, if symptoms are worse on older leaves the most likely culprit is manganese, and likewise, if the symptoms are worse on younger leaves, iron is the likelier nutrient deficiency. In wet periods or under root compaction or damage, symptoms become intensified. Additionally, clay sub-soils aggravate the problem.
Chlorosis is the most common problem that affects plants here in the valley. As always it is a good idea to bring a sample to the nursery for proper identification of the problem and its severity. Digital pictures (Please print them.) can also be useful, however, diagnosis over the phone is difficult at best. So bring your patient in for best chances of recovery.
Be aware, however, that changing the soil pH around a rooted tree is rarely a quick process. The following are a few ways to attack our common nemesis, which we at Adams Gardens will help you to choose based on the current health of the plant. If the plant is severely affected, consider spraying your foliage with a cheated-iron or manganese product, available year-round at the nursery. By testing the product on a small area at first, you may determine which element is limiting by watching for a response. During the growing season, the leaves should become darker green within a week or so if the limiting element was sprayed. This treatment only works on the leaves sprayed, so the effect is temporary and benefit’s the leaves currently expanded only. Newer leaves will not turn darker green.
The midterm treatment in terms of longevity and effective results also requires patience and attention: acidifying the soil can be accomplished by applying copperas or iron applied to the surface and watered. Depending on the severity of the condition, several applications may be required.
The longest-term treatment, usually begun once plants have returned to good health, deals with the maintenance of the correct soil PH level. This is generally done with annual to biannual treatments using soil sulfur. Soil sulfur will reduce the alkalinity and maintain the happy median that most plants prefer.
Depending on the time of year and the advancement of the chlorosis we will determine which plan of treatment is best. This way we can keep our favorite plants happy and healthy, even in some of the most difficult soils.