I have many hibiscus plants in my yard. All of them seem to not be blossoming and/or very sparsely. They all have numerous buds which seem to turn yellow in many cases and fall off. It seems strange that the whole yard of at least 50 plants are doing the same. The leaves also, esp. in the hybrids, are shriveling up in a shriveled cluster with the bud. It appears something is sucking the life out of it. The plants are nice and green. What is it and what can I use to correct it?
There can be several reasons for yellowing leaves on Hibiscus, including infestations of insects.
Neem Oil is a good treatment, it is safe for people and pets and should take care of any insects on the plants.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/answers-to-what-causes-hibiscus-leaves-turning-yellow.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-sticky-leaves.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
Many yellow leaves...why?
Here is a link that will help you pinpoint the cause.
My freshly planted blue hibiscus has a limp look and some yellow leaves falling off.
The soil will need to be kept moist but not soggy. If the roots dried out, the plant will suffer greatly, and possibly not survive.
Make sure the soil is well draining, if the soil does not drain and the roots sit in water, the plant also will die from root rot, or develop a fungus.
Make sure you have planted in a full sun location. Your plant needs a good 6 hours of sunlight.
Make adjustments to the watering and wait and see.
You can prune back the plant, by 1/3 to help it recover.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/transplanting-hibiscus.htm
They are planted outside. Could you suggest a way to make the plant less appealing to eat?
Keeping your Hibiscus growing healthy will help but several insects to like to feed on Hibiscus.
Neem Oil is a good treatment.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-sticky-leaves.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
Do the flowers open and close, or once the flower has bloomed, does it close and die?
The flowers on a Hibiscus last about 24 hours and then will drop off the plant.
Here is a link with more information on care requirement.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm
Why are the leaves turning yellow and falling off?
This is a common occurrence with Hibiscus.
Here is an article that will help you.
My plants did not die this winter. The branches are long and leggy. Do I leaves them like that or trim them? And how and where do I cut?
Prune the plant per the directions in the link below.
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm
https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm