Requirements for Healthy Rose Growth

• Roses should be planted in full sun. The Oregon State University Extension recommends planting locations offering about six hours per day of full sunlight exposure. Depending on the type of rose, some variations will also thrive in partial shade. Roses should receive 2 inches of water weekly from the end of April to about the first week of September. Along with watering and sunlight, roses should be pruned to remove diseased or dead leaves and canes. The best time to prune roses is after the last frost of the season. When cutting back diseased and dead canes, flowers should be "dead-headed" (removal of dead and wilting blossoms.) The soil should be well drained and boast a pH level of about 7. OSU recommends adding 1 cup of lime for each rose bush if your soil tests at a pH level lower than 7. Test kits are available at garden centers.
  
  

Causes of Leaf, Flower or Root Rot

• The main causes of rose rot are over-watering and poor soil drainage. Water pooled around the base of the rose bush encourages the growth of fungi, root rot and plant death. There are many types of fungi that attack roses and most depend on where you are located and your weather conditions. Soils heavy in clay content do not drain well and should be mixed with sand and nutrient-rich organic matter such as manure or mulch.
  
  

Evidence of Rot

• Rotting roses will be evident in many ways. Roses and Everything About Them website says that when roses begin shedding yellowed bottom leaves, leaving behind barren canes it is a good sign that the roots are rotting. Fungus sets in around the roots and chokes off the air circulation which prohibits the leaves from absorbing nutrients. Sometimes the evidence is very visible in the form of mold growth, black or white spots, curling leaves or moss growing around the base of the bush. All of these conditions are caused by over-watering and bad drainage. Molds and other disease can sometimes be treated, but roots that are rotting almost always means the demise of the rose bush.
  
  

Treatment and Prevention of Rot

• Powdery or black spotted leaves are caused by fungal diseases. The leaves should be removed immediately and discarded away from the infected rose bush. Failure to remove evidence of the fungi-infected parts of the bush will result in spreading of the disease. Roses and Everything About Them website suggests mixing 1 tbsp. of baking soda with liquid dish detergent in 1 gallon of water. Spray all infected bushes weekly. Baking soda will inhibit the growth of the fungus. Air circulation should be increased around rose bushes by thinning canes if the bushes are planted too close together. Rot is encouraged by too much water and underexposure to sunlight which is necessary to dry out the water on the leaves, flowers and around the base of the bush.