While Ranunculus is the name of a genus that includes hundreds of species, R. asiaticus is the species most typically grown in the home garden. Ranunculus thrives in cooler temperatures and may not survive extended periods of temperatures over 60 degrees Fahrenheit. Grow it indoors if you experience warm weather in the fall. Officially, the plant is hardy to U.S. Department of Agriculture plant hardiness zones 8 through 11.
Wherever you choose to grow your the ranunculus, provide it with lots of sunshine and good air circulation to avoid fungal diseases. For added protection, treat the ranunculus with a protectant fungicide.
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Type of Fungicide
The ideal fungicide to use to protect the ranunculus contains the bacterium, Bacillus subtilis. While this biological fungicide does eradicate powdery mildew, it is more effective at preventing the fungus from infecting the plant.
Time the application carefully as the product degrades off the plant after a week or so and is only effective if applied before the spores land on the plant. This typically occurs during periods of high humidity and moderate temperatures.
How to Apply the Fungicide
The product linked to above is ready-to-use and requires no mixing. If you purchase a concentrate, or you’ll be spraying more than a few ranunculus, use a spray tank Fill the spray tank with half the amount of water listed on the product’s label. Swirl the tank as you add the specified amount of fungicide. Finish filling the tank with the required amount of water, swirling the tank as you do so.
Spray the fungicide on the ranunculus until it is covered and the product just begins to drip from the plant. It is important to continue swirling the spray tank during application to ensure that the product remains mixed in the water.
Reapply the fungicide if it rains within four hours of application; otherwise reapply every 10 days to protect new growth.