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Monday, October 13, 2014

Rose Leaves Turning a Bright Yellow and Wimpy

Q. My vining roses have bright yellow and wimpy leaves. Am I over watering? Under watering? I have fertilized, added sulfur and iron too. 

Readers rose vine
A. This subject of whether a plant is over watered or underwatered is difficult to answer remotely. From your description, it sounds possible you are overwatering but probably not under watering.
Why don’t I think you are under watering? If you are under watering I would expect to see more leaf scorch and dieback on the leaves. Yellowing of the leaves of any kind is called “chlorosis” and can come from a number of sources including overwatering.
When yellowing or chlorosis is due to a lack of available iron then we will call it iron chlorosis. Chlorosis or yellowing due to a lack of available iron usually makes the leaves yellow with green veins. When iron is severely lacking, the leaf may be entirely yellow and scorched, but these are extreme cases.
Typical iron chlorosis with green veins on peach
Surround your roses with wood mulch, not rock mulch. If these plants have rock mulch surrounding them, rake it back a couple of feet and apply a couple of inches of compost first followed by some wood mulch. In this particular case do not use decorative bark mulch until the plants begin to recover. Decorative bark looks nice but it doesn’t do much for the soil.
Apply an iron fertilizer in the form of an iron chelate before you cover the soil with mulch. The chelate should be in the form of EDDHA which should be listed in the ingredients. The type of iron you add is very important. Mix the iron chelate in a bucket of water and pour it all over the soil above the roots or sprinkle it on dry and water it in. Don’t leave it on the surface because it is sensitive to sunlight.
Iron chelate with EDDHA on the label
Also, fertilize with a rose fertilizer or a fertilizer that has been formulated for flowering trees or shrubs. Avoid watering daily and try to give your woody plants a couple of days rest from any additional water before you irrigate again. Having wood mulch on the surface will help.
Specialty fertilizer formulated for roses
Always keep wood mulch a few inches away from the trunk of any plant to prevent stem diseases such as collar rot from occurring.

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