Gardenia Problem

Question

What is wrong with my Gardenia? Photo’s attached..

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Answer 1

This is a case of multiple, severe infections. I see algal spot, bacterial spot, and sooty mold, which will be fungal.

Something this severe will not be an easy cure. The first step will be treating with the fungicide of your choice, however. This article will help:

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

Next will be correcting the environmental factors causing the issue. This is usually overwatering, or it can be insect issues that cause infections.

Here is an article that will offer information on how to keep these picky plants healthy:

https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm

Answer 2

I suspect that you have pests in your gardenia causing the spots: white aphids and either white scale or mealy bugs (cousins of scale). As these pests feed on plant sap from the leaves, they leave clear, sticky honeydew (an excrement) that fungi turn black and is called sooty mold. The sooty mold is not particularly harmful but it may yellow out some leaves that do not get enough sunlight. You should address the pest infestation first and then clean the sooty mold. Most of the pests will be sucking sap off the leaves so hit them with the hose. Many will die from injuries. Some will fall and climb again so hit about 3 times after you notice them returning. Clean the leaves similarly -with a high pressure hose- or by hand, using a wet cloth or a wet sponge to remove mold residue. These pests may visit again next year so, make a note in the 2022 calendar to be on the look for them about a month before you first noticed them this year.