Why Are My Plants Turning Yellow?
One of the most common plant problems in Utah is a disorder called iron chlorosis. It is not caused by a particular pathogen, but usually occurs when plants are not able to absorb enough iron in alkaline soils. The visible symptoms of the disorder are easily identified. The leaves turn bright green to yellow and can eventually turn white. The veins usually remain a darker green. In moderate to severe instances, the edges of the leaves may scorch or appear burned. If the problem persists year after year, branches may even die.
There is no easy or permanent remedy. Even with successful treatments, plants usually need to be treated annually. Unfortunately, many commonly used landscape plants are not adapted to alkaline soils. Some of these include silver maple, red maple, Autumn Blaze maple (a hybrid of silver and red maples), quaking aspen and birch. Purple leaf sand cherry and Japanese spirea shrubs are also moderately susceptible. Many fruit crops, including raspberries, strawberries, peaches and apples, also get iron chlorosis.
The severity of the symptoms of iron chlorosis can be compounded by overwatering. Excessive soil moisture makes it more difficult for plants to absorb many nutrients, including iron. Once plants are established, they should be deeply watered and allowed to dry between irrigations. Incorporating compost into the soil around the drip line of infected trees and shrubs can help alleviate iron chlorosis problems. As the compost breaks down in the soil, its individual particles tend to free up certain micronutrients, including iron.
Consider this information for treatment.
• Many products are available to combat iron chlorosis. However, there are also many complicating factors that make certain products less effective. If a soil application is to be made, the most effective treatment is to apply chelated iron containing FeEDDHA in the early spring before the plants leaf out. Many brands are available, and garden center employees can assist. During the growing season, foliar-applied iron products can be moderately effective but frequently need to be re-reapplied to new growth, and they cannot be applied in the heat. As with any chemical, always read the label instructions.
• With larger trees, it is possible to drill into the trunk and insert capsules containing iron into the drilled holes. These capsules release iron into the conductive tissue and last one to two years. However, the trunk may be damaged if this process is repeated over a number of years.
•The best way to avoid iron chlorosis is to use plants in the yard that are more efficient in absorbing iron. The ultimate decision regarding treating landscape plants is expense over time. For more information on iron chlorosis along with a list of more resistant plant species, visit: http://tinyurl.com/usuironchlorosis.
By: Taun Beddes and Jaydee Gunnell - Aug. 2, 2012