Q.Why have all of my flower buds dropped off of my Formosa, again.
My formosa is 6′ tall, in a large tub. It stands out in the sun all summer and I bring it into my frost free conservatory in the autumn. With the same problem last year, I was advised to remove it from it container, and saw off the bottom half of the root ball. fill with fresh compost and replace. This I did, and during the summer, it was covered in buds.
However once again, all of the buds have fallen off without opening?
Certified GKH Gardening Expert
I do remember this. Have you made sure to remember to drill holes in the container? without having proper drainage it will throw off the soil environment.
Other than this, and depending on the type of compost, and what animal manures are in it, there could still be too much nitrogen and not enough phosphorus and potassium.
Another thing that is common with this issue is an extreme change in environment. I wouldn't recommend full sun since it will be moved into an area in which the windows filter out some of the spectrum of light. Even if it receives direct sun through the window, a test on light intensity and spectrum will reveal quite a loss.
This drastic change will prevent flowering as well.
Have you checked the soil pH? These will not like to go above 6.0 in pH. This will certainly cause an issue.
Try correcting these last few issues and it will continue to flower.