My plant is full of buds, but right before they open, the green healthy looking buds fall off the plant. The plant is planted in the soil, not a pot.
What you describe is often caused by insect problems. Here are more details:
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-flowers-hibiscus-blossoms-falling-off-plant.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-thrips.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/blossom-midge-in-plants.htm
The plant had one flower on the bottom. The plant is about 8 years old and has bloomed and spread every summer.
If there are few or no flower buds, this could be a soil fertility issue. You may have excessive nitrogen in the soil or too little of another nutrient.
Hibiscus plants also prefer acid soil; you may want to get a soil test to see if it needs to be acidified.
It is also common for hibiscus buds to fall off without opening in times of environmental stress, such as high temperatures.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-fertilizing.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-flowers-hibiscus-blossoms-falling-off-plant.htm
I have a large blue hibiscus, but it looks like it is dying. I found on the trunk low on the ground big quantities of white stuff with ants all over. Is this scale, mealybugs, or what? I live on central coast of CA. What can I use to kill This? I really love this plant and don't want to lose it. Thank you.
Sounds like you could have woolly aphids, mealy bugs or scale bugs. There are photos and additional links which may help you positively identify your unwanted visitors (and correct any damage they may have done) in these links:
https://www.gardeningknowhow.com/plant-problems/pests/insects/woolly-aphid-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm
After a very hot day yesterday, I gave the garden and plants a good watering. When I watered my Hibiscus, I also gave the foliage a spray. Today, I notice that some of the flowers have wilted. Did I cause that by spraying the plant itself or am I over-watering? I tend to water about every three days on average, sometimes every two days.
If you sprayed while it was still hot, the water may have heated up on the leaves and burned them. The plant will recover, but it's best to spray in the early morning or in the evening during the hot part of summer. Or, you may be watering too infrequently. During the very hot weeks you could try watering every other day or every day and see if that helps.
Something is eating my hibiscus plant. The leaves look like lace. What should I use to get rid of pests?
This could be Hibiscus sawfly or several other insects. These articles should help:
https://www.gardeningknowhow.com/plant-problems/pests/insects/skeletonized-plant-leaves.htm
https://entomology.uark.edu/Arthropod-Museum/mallow-hibiscus-sawfly.php
I bought a healthy hibiscus Luna red at Lowe's today. I live near Pensacola, FL in zone 9. I plan to plant this plant in full sun tomorrow. Any hints? Thanks. It is about 2 feet up from the ground.
This is a good time of year to plant it. These articles give some advice:
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/transplanting-hibiscus.htm
Do they flower while inside for the cold months?
Yes, hibiscus can flower indoors throughout most of the year if it gets enough light. Here are more details: