Northern & Central Midwest
Spray Roses with Cornell Fungicide Formula
Researchers at Cornell University provide the following natural fungicide: In one gallon of water add 3 to 4 teaspoons baking soda, 3 to 4 teaspoons vegetable oil, and one-half to one teaspoon dish detergent or insecticidal soap. Spray until it drips off the foliage, every 3 to 4 days.
Mulch, Mulch, Mulch Your Roses!
Add a 2- to 3-inch layer of fresh mulch in early spring around all your roses. The mulch will help cover any overwintering spores and prevent them from splashing on the leaves. Additionally, mulch is a great way to keep the soil cool. Besides, it looks great!
If you are growing repeat bloomers, such as hybrid teas and grandifloras, fertilize them in spring and again lightly when blooming. Avoid high nitrogen fertilizers as they make lots of succulent leaves and few blossoms. Choose a rose formula with higher phosphorus. Remember that organic fertilizers help improve the soil, too.
Use Bordeaux Mix For Fungus on Roses
If the baking soda formula isn't successful, Bordeaux mixture might help. It is a mix of copper sulfate and lime (calcium carbonate). Copper is a known fungicide, and the lime acts as a surfactant to make it stick. It can be toxic because of copper buildup in the soil, but it's technically an organic spray.
Cut Roses Properly to Keep Them Healthy
In spring and early summer and especially on newly planted roses, take only short stems when you cut for a bouquet. Roses are sensitive to the loss of leaves during these times, and removing too many can stress the plant. Cut in early morning or evening for the longest lasting bouquets.