Chlorosis is an Easily Solved Problem

By Jim Janke | Aug 08, 2013

Do you have a plant whose leaves look like this? Chlorosis is a common problem in annuals, perennials, houseplants and shrubs. Here are some simple ways to deal with it.

Chlorosis occurs when a plant can’t manufacture enough chlorophyll. The leaves turn yellow, and the plant may die unless the problem is corrected. Chlorosis may be caused by a lack of sunlight; damaged roots from poor drainage, mechanical injury, or soil compaction; herbicide damage due to misapplication or overspray; or plant disease. So the first thing to do when you see yellowing of the leaves is check for one of these causes.

Another frequent cause is when nutrients aren’t getting to the plant because the pH is too high or low. Every plant has a desired pH range where its roots most efficiently absorb nutrients in the soil; if the pH is outside this range chlorosis can occur. (For a list of optimum pHs for specific plants, go to: http://www.ces.ncsu.edu/depts/hort/consumer/quickref/soil/pHplants.html.)

My petunias next to the driveway sometimes turn yellow because of high pH, especially after heavy rainfall has leached the acidity out of the soil. So I spray the leaves with a soluble fertilizer for acid-loving plants (like Southern Ag’s MaxAcid® or Scotts’ MirAcid®) at the rate recommended on the label. These fertilizers have iron and other micronutrients as well as soil acidifiers. Spraying the solution on the leaves accelerates their intake into the plant tissue. A couple of applications normally take care of the problem.

Sometimes an entire group of landscape plants will exhibit leaf yellowing. When this happens I get the soil tested and add either sulfur or lime depending on the results of the test. If the pH is too high applying an acid-loving plant fertilizer will get quick results, but applying sulfur to the entire area is a better long-term solution.

Even in the greenhouse pH can be too high if you are using water from a water softener or if pots and flats were not rinsed well after washing.

When you solve one pH problem be careful not to create another. My worst pH headache was rhododendrons planted in a field of ground cover. The ground cover liked a higher pH than the rhodos. If I satisfied one plant’s pH desires, the leaves of the other turned yellow. I tried to keep the ground cover happy, adding sulfur to the area only immediately around the rhodos. But this didn’t work, and eventually the rhodos were pulled out.

Keep an eye out for chlorosis in your garden.

Jim Janke is an Extension Master Gardener Volunteer in Haywood County. For more information call the Haywood County Extension Center at 828-456-3575.  © 2013 NC State University.

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