1: Milk Spray
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Although this one may sound a little odd, try spraying down your zinnias with a milk spray made with 1 part milk and 10 parts water. Proteins in the milk can actually help break down the fungal spores and combat powdery mildew really well.
This one is also great for other plants with powdery mildew, like strawberries and zucchinis!
2: Baking Soda + Mild Soap
Mix 1 tablespoon of baking soda with half a tablespoon of mild dish soap in a gallon of water and spray your zinnia plants with it at least once a week.
3: Potassium Bicarbonate + Horticultural Oil
Like the soap and baking soda spray, you want to mix in 1 tablespoon of potassium bicarbonate with 2 tablespoons of horticultural oil to create a stronger mildew-combating alternative.
For more gentle, chemical-free solutions like this, check out these natural garden sprays that tackle pests and diseases without harming your plants.
4: Neem Oil
Plan your best garden yet! This printable 2026 Sowing Calendar tells you exactly when to plant your favorite vegetables, herbs, and flowers for a thriving garden all year long.
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While neem oil is conventionally used to reduce pest populations in the garden, it can also help fight fungal infections if used correctly. Use 2 tablespoons of neem oil per gallon of water and spray the solution onto your zinnia plants for quick relief. Use this neem spray once weekly for the best results.
5: Garlic Extract Or Compost Tea
Although there aren’t any particular studies done on this for zinnias, some research does show that garlic and tea might have some antifungal properties that could be of use in the garden.
And while you’re treating powdery mildew, don’t forget to deadhead your zinnias regularly to keep those blooms coming strong all season long.
How To Apply Treatments Safely & Effectively?
So, application of treatments isn’t rocket science. Since we know that these methods work effectively, we can use them safely and without worry.
Plan your best garden yet! This printable 2026 Sowing Calendar tells you exactly when to plant your favorite vegetables, herbs, and flowers for a thriving garden all year long.
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It’s generally a good idea to time your applications around early morning or evening, and not when the midday sun is blasting heat. Make sure to coat your entire zinnia plant evenly with the solution and not miss any affected areas.
In case of heavy damage, you want to cut off all infected parts of the plant and dispose them off as far away from the garden as possible. DO NOT compost them at any cost!
When It’s Okay To Just Let It Be…
While immediate action is typically encouraged, if the infection seems mild, you can just let the plants be. They don’t always need treatment and can often make surprising recoveries on their own.
Your number one indicator for whether to intervene or not should be bloom development. If it’s stagnant, changes may be necessary; if not, just let the plants be.
Let’s Conclude
Powdery mildew can be a serious hindrance in the way of zinnia blooming. It can make blooms stagnant and even stunt overall growth if allowed to dwindle on plants for too long. Take action as necessary and give organic remedies a try; you’ll definitely be surprised by how well they work!
