Can you tell me what this is on the gardenia leaves.  It does rub off but I'm thinking it's mildew and don't know what to use to eliminate it.

-Joan

It's hard to tell but it is probably Sooty Mold. This is usually caused by an insect (probably whitefly). There are different ways to solve problem.  My favorite is with Bonide tree and shrub. Lasts a full year. I keep it and other remedies at the Nursery.

-Sam