Whether you planted the rose bushes yourself or have been taking care of them in your yard, you want them to look good. Walking by them one day to see the leaves turning yellow can be disturbing, but it is not a symptom you should ignore (unless its fall and the leaves are changing, but even then rose leaves tend to turn a rust red, not yellow). Here's what you need to do to identify why the leaves are turning yellow, so you can treat the problem and reverse the process and prevent your rose bush from dying.

One of the most likely causes of yellow leaves is iron chlorosis. In general, chlorosis is caused by iron deficiency. It is particularly common in the Southwest, where soil tends to have a high calcium carbonate content. Chlorosis can usually be remedied by soil treatments. Add 1-2 pounds of iron sulphate or sulphur per hundred square feet for a single application, followed by mulch that is at least four inches thick.  For an immediate treatment, spray your roses' leaves with an iron sulphate solution comprising of one ounce of iron sulphate diluted in three gallons of water. Most garden centers will carry one or two products like this.

During the hottest parts of summer, heat stress can cause yellow leaves. This is especially true after a wet, cool spring. This is common among new roses, as they have not had enough time to establish root systems that support leaf transpiration. Clues that heat stress is the culprit include scorched leaf margins and dark petal edges on blooms. To treat heat stress, mulch heavily around the roots and prune to encourage root development. Be sure to water deeply enough so that the water is getting 2-3 feet below the surface. You want to encourage deep root growth, and short shallow waterings can sometimes train roots to grow more shallow.

Overwatering is another source of yellowing leaves. Soft, brown cane centers, droopy mature leaves, and blooms that do not open fully are also signs of overwatering. To treat this situation, improve the drainage by increasing the amount of organic matter in your soil and replacing any claylike soil with loose garden soil.

You can add top-dressings like mulch to the soil to amend it, but really the best and only effective way to amend soil is to dig down about twelve to twenty-four inches and mix in the soil amendments. Clearly this is going to be a problem if your roses are already planted and established in soil that has poor drainage. Digging around your roses is an acceptable solution. One way to know for sure that your soil has poor drainage is to dig a six inch hole and fill it with water. If there is still water in the hole an hour later, you have a drainage problem.

If you use a large amount of water-soluble fertilizers, yellow leaves may be the result of salt stress accumulated from nitrates in the fertilizer. Salt stress also reduces plant growth and causes scorched leaf margins. Treat salt stress by switching to organic fertilizer with a low salt index. You can leach salt out of soil by running lots of water through it, but this technique can be hard on your water bill.