Why Are My Gardenia’s Leaves Turning Black?

May 30, 2013 | By | Comments (7)
Miami Supreme' gardenia

‘Miami Supreme’ gardenia. The garden’s most fragrant plant. Photo by Steve Bender.

When terrible things happen to your plants, who are you going to call? The all-knowing Grumpy, of course! Who else would know why your gardenia’s leaves are turning black and what you can to fix it?

The photo above shows gardenia the way it’s supposed to look. Voluptuous, seductive, waxy, white blossoms redolent of perfume so intoxicating it could make Mother Teresa randy. Glossy, deep green, healthy leaves. So what’s going on  in the gross picture below?

Sooty mold on gardenia

Sooty mold on gardenia. Photo: farmcarolina.com

A desperate Lisa Phillips writes: “My gardenia bushes are being attacked by some kind of small insect and black mold.  I have sprayed the bushes with detergent and water several times and treated with Sevin dust, but they bushes are still showing mold.  HELP! I don’t want to lose these bushes, as they are an old variety that produces large fragrant blooms.”

Grumpy replies: Relax, Lisa. Release those endorphins. Grumpy has come to the rescue. Your gardenias are probably under siege by sucking insects, such as aphids or whiteflies. These bugs secrete a sticky honeydew as they feed. Black, sooty mold then grows on the honeydew. Get rid of the bugs and the mold will go too.

To do this, spray your gardenias according to label directions with horticultural oil, making sure to wet both the tops and undersides of the leaves, as well as the stems. You may have to spray more than once. Or apply a systemic insecticide that’s absorbed by the plant and lasts a long time, such as Bayer Advanced Tree & Shrub Protect & Feed. You can get both products at garden centers.

One more problem expertly solved!


  1. Mario Rojas

    Great information my plants are been attacked by this kind of fungus, thanks for sharing.

    April 5, 2017 at 6:11 am
  2. Angelina Wormald

    I have the same problem with my gardenias. My issue is that I now have a lizard family tending to my gardens as well and they are eating the bugs…I can’t spray any chemicals in any of my gardens. How can I keep my gardenias alive and flourishing and keep my lizard family alive as well?

    March 5, 2017 at 8:28 am
  3. Quiet bob

    I respect holy persons also, but it is obvious that the reference to Mother Theresa was not disrespectful. It was a metaphor. No intent, no foul.

    February 26, 2017 at 10:30 am
  4. Anthony G. Coppola

    Really . . did you have to say, “make Mother Teresa randy”? Some of us still respect holy people and you did not need to disgrace a holy woman by mentioning her getting sexually intoxicated off a gardenia.

    February 16, 2017 at 11:07 am
  5. Melora

    Thank you for this article. We just pruned our gardenia way back. It had been neglected for many years. We may sacrifice next years blooms but I don’t want to lose the bush forever. We will start spraying it to get rid of those bugs and hope to get the beautiful bush back.

    September 16, 2015 at 6:57 pm
  6. Margaret Macy

    I hate aphids

    May 30, 2013 at 6:54 pm
  7. Arthur in the Garden!

    Whiteflies love Gardenias here in North Carolina. I spray a few times a season and it keeps them and the sooty mold under control .

    May 30, 2013 at 11:17 am

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