Here are several homemade recipes for preventing fungus such as powdery mildew or blackspot on perennials. The emphasis here is on prevention. That means these methods are meant to be used before you notice a fungal infection.
1tsp. baking soda
few drops Trounce or 2 drops liquid soap
2 cups water
Mix and spray generously on plants. Repeat every two weeks.
- Spray roses and new seedlings with a “tea” made of ground cinnamon.
- Steep and cool chamomile tea (4 tea bags in 2 cups water), spray new seedlings to prevent “damping off”.
Heat and humidity in mid summer are key contributors to the development of fungus. Perennials prone to fungus should be spaced in a way that promotes air circulation.
Some perennials that are susceptible to powdery mildew are: Garden Phlox and Bergamot (Bee Balm)
Black Spot typically strikes roses.