So your orchid has finally bloomed, but then you’ve noticed that there are spots all over the flowers. What are those spots, and what can you do to prevent them? This post describes all these topics, so keep reading.
Table of Contents
Spots on Orchid Flowers
What causes the spots?
Some types of orchids, namely Phalaenopsis and Cattleya, are very prone to a fungus named Botrytis. It causes spots on the flowers themselves. All of the photos in this post are my own photos taken in my greenhouse of a Phalaenopsis orchid with Botrytis.
Botrytis will cause small spots to appear on the orchid flowers and they can range in color from greenish, to brown, black and gray.
Treatment
Unfortunately, once Botrytis happens, any treatment will not remove the spots, but it can prevent it from spreading to other orchid flowers. The American Orchid Society reports that a suitable fungicide to use is Daconil or even Physan 20. Some people have success with 1/2 teaspoon of baking soda mixed into a quart of water, and then this solution is sprayed on the flowers.
If you choose to use a spray, test it out on one flower first and wait a day or two to make sure it doesn’t negatively affect it.
If you don’t want to use any sprays, you can discard any affected flowers and read up below on ways to prevent the issue in the future.
4 Ways to Prevent Botrytis
Understanding the conditions in which botrytis thrives is key to understanding how to prevent it. I’ve never experienced botrytis on my orchids inside the house, but I’m battling it in my greenhouse because the conditions are more favorable for botrytis.
Botrytis thrives in certain cultural conditions. It will winter over on dead or dying plant material. The fungal spores are produced and distributed in cool, damp conditions (especially if you have poor air circulation).
It is a common fungus in the environment, so the best way to manage it is to provide conditions that it doesn’t like. Here are 4 things that you can do to prevent Botrytis infections.
1. Keep Your Growing Area Clean
Always remove any spent flowers and dead plant material. Keep your growing area clean and you will lessen the change of botrytis spores spreading to your other plants.
2. Increase Air Circulation
Air circulation is key to preventing botrytis and other fungal pathogens as well. Humid, cool growing locations with poor air circulation can really kick this fungal infection into high gear. Adding a fan or ventilation in your growing area will help a lot.
3. Keep Temperatures in an Appropriate Range
If you can keep nighttime temperatures above 65°F, this can help prevent infection. But for best results, it should be combined with a reduction in humidity (the humidity in my greenhouse is often above 90% so it’s a struggle for me!)
4. Be Careful When You Water
Avoid getting any water on the orchid flowers themselves when you water or mist your plants. If water remains for a long period of time on the flowers, especially in cool, humid weather, it can provide good conditions for botrytis growth. If you have good air circulation, this will help dry things out. I’ve added more fans in my greenhouse to provide just that.
Remember, if your humidity is too high (with poor air circulation and cooler temperatures), this can be very problematic. If you’ve had Botrytis and you are growing indoors or in a greenhouse, increase ventilation or use a dehumidifier to help.
If you can, water your orchids early on in the day so that your plants can dry out before nighttime.
If you want to learn all about how to get your orchid to rebloom reliably and have healthy, thriving moth orchid plants, don’t miss my signature, online orchid care course, Become an Orchid Master. It also includes bonuses with support from me, personally, to guide you in your orchid journey!
