A common problem I hear when talking to fellow gardenia care experts and lovers is that of black gardenia leaves. We strive to keep our gardenia healthy with lots of loving care, only to see our prize plants succumb to black leaves. So what are the causes of gardenia black leaves?
 

The Gardenia Care Expert On Causes of Gardenia Black Leaves

There are a number of causes of gardenia black leaves.

• Is the actual gardenia leaf turned black or is it covered in a black residue that can be removed by hand? If the black can be removed then your gardenia black leaves are caused by a fungus growing on the gardenia leaves namely sooty mould. This is the most common cause of gardenia black leaves.
  
  

  Gardenia black leaves caused by sooty mould

  While sooty mould isn’t harmful to the gardenia plant it looks very unsightly. Sooty mould affects gardenias and citrus plants and is a common cause of black leaves. Where does it come from? Well the sooty mould on your gardenia black leaves is most probably growing and feeding off the sticky excretions of sap sucking insects like aphids and white fly. While the mould itself isn’t harmful to the gardenia a gardenia care expert would look to eradicating the cause of the problem namely the insects.

  The insects feasting on you gardenia can be treated with horticultural insecticide although I feel this is a little harsh on your garden environment. I only use a green / organic insecticide sparingly and as a last resort if the insect infestation is particularly heavy and brushing and squashing isn’t addressing the problem. The mould on your gardenia black leaves can be simply washed off, but if you don’t address the insect problem you’ll find that you are doing this more and more.
  

  

  Aphids can be the root cause of gardenia black leaves

  You can try and prevent gardenia black leaves issues, by using horticultural oils and soaps but I believe your best protection is to try and attract more of the insects natural predators into the garden like ladybugs. As always when using chemicals and products always read the label and instructions and see proper advice if you are unsure.

• Is the actual leaf black? Gardenia black leaves can be caused by the gardenia plant being exposed to sub 50º temperatures. If you regularly experience sustained temperatures below 50º maybe you should investigate if your gardenia plant is suitable for your zone. If you know that the temperatures are about to drop then try covering your gardenias in order to keep them warm and keep out the cold.