|Four year old beds ,previously healthy plants , now some are starting to go yellow , green veins . Ones next to it could be OK. Daisey,Lupins,Bee Balm, cat mint . All perennials. One new bed made of mostly 4yr old composted horse manure .|
|Yellow leaves and green veins are often the result of a common problem called iron chlorosis. This is the result of either an iron deficiency or iron unavailable for plant uptake.
Iron levels are usually adequate in most soils. However, high soil pH makes it unavailable for plant uptake. In alkaline soils with a pH above 7.0, most plants are not able to take up iron. To check the pH of your soil, contact your local extension office for instructions on soil testing.
Once iron chlorosis is confirmed, several methods may be used to provide iron to affected plants. Here are several ways to treat for iron chlorosis.
Foliar application - If a rapid response is needed to correct a chlorotic condition, a foliar spray with iron sulfate or iron chelate solution may be applied when the tree is in full leaf. This treatment is not very effective however. It is only temporary. New growth that emerges will be chlorotic.
Soil treatment - Since iron chlorosis is often the result of high pH or alkaline soils, lowering the pH would be the most reasonable solution to prevent chlorosis. It is difficult however to lower soil pH at depths of 18 to 24 inches. The best approach is to add iron to the soil under the tree canopy. This treatment remains effective for two to three years.
Hope this information helps you correct the problem with your plants.