Question
From reading several articles, I think I have spider mites on my indoor gardenia plant. There are cobwebs and residue on some of the leaves. Some of the articles recommend spraying the leaves with a solution of Dawn detergent and water. Do you agree with this? Will this solution harm the roots? Any information will be appreciated. Thanks

Answer
Hi Jan,

I always worry a bit when someone has found information elsewhere. That is because there is so much incorrect indoor plant information readily available.

Spider mites are so tiny that you can get a half dozen of them on the head of a pin. They look like specks of dust and they cause the leaves to have a mottled appearance. Their webs are very wispy and difficult to see unless they are misted and the water droplets make the webs more visible. Spider mites do not leave any residue. So I have some concern that you may have problems other than spider mites. If you post a clear photo here or email it to my email address below, I can more properly ID the mites for you.

To treat spider mites, fill a spray bottle with water and add a squirt of any liquid dish soap. (It does not have to be Dawn or any other brand name!). The key is to spray all leaf and stem surfaces of the entire plant until they are dripping wet. If you miss even a few between the spray droplets, they will reproduce and the problem will return. So thoroughness of coverage is of paramount importance, no matter what you use to treat them.

Some of the soap solution will drip into the soil and that is not a problem. However, I don't recommend pouring it into the soil. Spider mites survive only on plant tissue and do not live in the soil.

When a plant has pest problems, it very often has other problems, as well, because plants under stress are much more vulnerable and appealing to pests. Gardenias are not easy indoor plants. They require lots of very bright, but mostly indirect light. They must also be kept quite potbound and unnecessary repotting often leads to root rot. When properly potted and given proper light, Gardenias should be watered thoroughly as soon as the top half-inch of soil is dry.

Finally, I will note that mites thrive in very warm, dry air.

Good luck with treating the spider mites.

I have written detailed articles on treating indoor plant pests and on Gardenia care that I will email for free to you (or anyone else) who emails a request to me at [email protected]. I have also written an indoor plant care book in a PDF format that I can sell you if you contact me at my email address.

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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