What Does It Mean When the Leaves Fall Off Your Rose Bushes in the Spring?

Blackspot

• Wet, warm weather with temperatures above 75 degrees F and falling leaves may mean the rose has blackspot. This fungus causes black spots on the leaves that eventually develop yellow rings around them. The leaves turn yellow and fall off as the fungus progresses. Remove infected leaves and those that have fallen around the bush. Mix 1 tbsp. of baking soda, two to three drops of mild dish soap or 2 tbsp. of fine horticultural oil into 1 gallon of water. Spray the bush thoroughly, making sure the bottoms of the leaves are coated. Spray the bush again after it rains. Sulfur dust, lime sulfur or commercial fungicides may be required. Follow the manufacturer's application recommendations.

Downey Mildew

• Temperatures below 75 degrees F and high humidity are the right conditions for a downey mildew fungal infection. This infection causes dark purple-red irregular-shaped blotches and streaks on the leaves and possibly fuzz on the underneath. Leaf tissue within the blotches dies and turns brown. Eventually, the entire leaf turns yellow and falls off, new stems die and the blotches spread to the canes. Prune off leaves and stems with symptoms and throw them in the trash. Mulch or debris around the rose should be removed. Hose the shrub down in the morning with a garden hose. Mix 2 tbsp. of fine horticultural oil, 1 tbsp. of mild dish soap and 1 tbsp. of baking soda into 1 gallon of water. Spray the rose bush thoroughly with the mixture, including the bottoms of the leaves, stems and soil around the bush. Spray the rose with the mixture every two weeks until the humidity drops and temperatures warm up.

Rust

• If the rose leaves had rusty or bright orange spots before falling off, it means the bush has a fungal infection known as rust. The spots can appear powdery or warty and commonly form on the stems and leaves. The spots turn dark brown and eventually black. Small rose bushes will be killed if they are not treated right away. Prune off any parts of the bush that have rust spots and throw them away. Fungicides containing oxycarboxin can be used to kill this fungus. Follow the manufacturer's recommendations carefully.

Fertilizer and pH

• Roses should be given fertilizer in mid-spring, mid-summer and very late autumn or very early spring. If it has been over-fertilized, water the bush generously until the soil is well saturated two mornings in a row to help wash the fertilizer away. If the bush has not been fertilized, give it the manufacturer's recommended amount of a fertilizer formulated for roses. If the rose is relatively new, the falling leaves could be due to alkaline soil. Have the soil tested by the local extension office if the pH is questionable. They can also test for nutrients and recommend fertilizer or sulfur applications if necessary.