My hibiscus is very large and I would like to divide it. It is planted outside. Please help!
Generally, no. However, you can propagate the plant by cuttings. If the plant has gotten too large, you can prune it back in spring. These articles should help you with that: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-propagation.htm
Why do my hibiscus leaves have holes and look as if they are being chewed around the edges?
It sounds like the plant has a pest. There are several it could be. I would treat the plant with and insecticide. Check under the leaves and at where stems meet to see if you can see what the pest is exactly. They may look like fuzzy or bumpy spots and may not look pests.
How do I propagate a hibiscus?
Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-propagation.htm
The hibiscus leaves are green and begin to turn yellow in the middle of the leaf, then all the leaf turns yellow and falls. They are in pots in the yard and get the morning and noon sun. I am in FL for the winter months. There are no bugs on the leaves.
Most hibiscus in the winter tend to shed leaves (because the sunlight is not as intense in the winter), but just in case, make sure the plant is getting enough water and add some slow release fertilizer (like osmocote) to the soil.
My hibiscus has black powder on it. What is it?
This is sooty mold. This article has more information:
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
I have hundreds of tiny white bugs on my leaves and flower buds. They eat the flower and the stem falls off? What is it? How do I get rid of it?
It sounds like mealybugs. They are common this time of year on indoor hibiscus. This article will help:
https://www.gardeningknowhow.com/plant-problems/pests/mealybugs-white-residue-on-plants-leaves.htm
I have five hibiscus plants that thrived last summer. I left them in the ground during freezing weather (somewhat northern Florida). Now that they appear to be dead, is there any chance that they may come back if I trim the dead wood back to the ground?
As long as the stems are still alive, they will come back. This article will help you with caring for cold damaged plants: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm
As for cutting it back, I would wait until spring before doing so. This article should help: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm