Question
We have 5+ hibiscus plants in our garden window above the sink. It faces west. Some leaves on the various plants have been turning yellow and dropping off. Some of the plants have drooping leaves, like they need water, but are already wet. Then tonight we noticed a sticky substance on the backside of the leaf at the junction to the stem. Do you have any idea what we might be dealing with? We can't see anything on the back of the leaves; there does not appear to be any webs - just the sticky substance. Thank you for any assistance or suggestions you might have.

Answer
Rebecca,

Overwatering can cause the roots to rot then the plant can no longer take up water and the leave droop no matter how much water you put on them. The more water you give them just causes the remaining roots to rot. You are right the sticky stuff indicates insects and it is most likely spider mites or aphids even though you do not see webs. First take each plant to the bathtub and remove the drain tray and drain off as much water as possible. Then do not water the plant till the soil is dry.  To allow the roots to grow back you must follow the directions below.

The leaves will continue to turn yellow and fall off for awhile because the damage has been done. The plants may loose most of their leaves. It will take time for the roots to grow back first before you will see leaves grow back. You have to learn to water the plant without overwatering it.  When the soil feels dry insert a bamboo skewer from the grocery store like you would use to make shish kabobs or meat skewers on the grill. If the skewer comes out of the soil dry it is time to water, if it comes out wet it is not. Wait until the soil is dry to water it then water it enough that most of the soil is moist but do not give it as much as you have been giving it in the past, cut the amount by about half. An hour after you water it if there is any water in the drain tray suction it out with a turkey baster. Then do not water again until it is dry again. If you follow these watering instructions the roots will slowly grow back and within 3 months you will see new growth on top. You just have to be patient, it takes time. Keep it in the sunniest location possible and keep the drapes and blinds open. When the temperatures are above 60 degrees at night your hibiscus plants can go outdoors in a semi shady location on then east or west side if that is possible at your house, they will recuperate faster outdoors.

In the meantime as they recuperate from the root rot you also have to treat the insect problem. You need to spray the plant with rubbing alcohol in a spray bottle in the crotches of the leaves where you found the stickiness and on the fronts and backs of all the leaves. Spray them every other day for ten days then twice a week for 2 more weeks to kill any eggs that hatch. After that watch closely for signs of any more insects. Good luck.

Darlene