Indoor hibiscus

[Tyto Alba]

I've got 4 of these indoor hibiscus on the kitchen windowsill. They really are terrific, massive flowers, brightly coloured and they flower nearly all year. They are evergreen too.

The leaves on one of the plants has started to turn yellow, the veins of the leaves remain green longer than the rest of the leaf. Also, there is a small patch of fuzzy black stuff just where the stem meets the leaves on the back of the leaf.

I'm assuming this is some sort of disease, but what and how to treat?

A couple of normal looking leaves on the plant next to it has also got the black stuff.

What do I do?

[SueA]

Hi Tyto Alba, sorry I'm no expert on hibiscus but I think it sounds like they may have been over watered, they don't like their feet standing in water.They can drop leaves which are old & have turned yellow due to age even though they are generally evergreen, but as you say they still have green veins it could be some kind of deficiency, maybe magnesium? This could be due to irregular watering or maybe needing a feed.Hopefully someone else with more knowledge of hibiscus will come along & offer some advice, I would separate them from each other though as being crowded next to each other could cause problems even if it's not a virus or disease. Have you checked for aphids also , they could cause the sooty/mould effect that you describe & change the colour of the leaves if they have been sucking the sap from them?

[Tyto Alba]

Thanks Sue A.

I kept them fairly dry over the winter, and have only just started watering them again.......same with feeding. They haven't been overly wet, but maybe I have started watering too quickly.

I haven't seen any signs of aphids, but I will look more closely tonight.

I'm wondering whether I should remove the affected leaves, or if I should spray them with something. The sooty patches are only a few mm wide and only occur where the stem meets the leaf.

[SueA]

Hi Tyto Alba, you sound as though you're doing everything O.K. as far as I know. I think I'd be tempted to take off the affected leaves too, just be careful if you cut them off to wash/disinfect the scissors/snips you use in between so you don't spread anything around from one plant to the other or wash your hands if you pull them off. Good luck, hope they recover.

[bramble]

Hi Tyto Alba,
I have some indoor hibiscus and find that tap water tends to turn the leaves yellow.
The black i would think is sooty mould. Ezamine the underside of the leaves and see if there are any insects on.
Wash with soapy water and they should be ok. I have had this happen to mine and after the soapy water treatment they were fine.

[Tyto Alba]

Thanks very much. I will do as you suggest.