Bougainvillea Losing Leaves
Three years ago we bought a Bougainvillea for our conservatory, for the first year it was full of lovely pink leaves. However, the year afterwards it didn't grow as many leaves and the pink leaves it had fell off very quickly. It also developed pale brown spots on a lot of the leaves. We removed as many of those leaves as we could, and eventually these spots seemed to reduce although not disappear altogether. This year, we have hardly had any new leaf growth and the plant is now looking quite sparse, and we're still getting the same pale brown spots on the leaves. We've tried reducing and increasing the water we give it and applied both a general plant food and a potash one, but nothing seems to be improving it. We're really, not sure what to do know, we don't want to lose the plant.
Yellowing or tan leaf spots can be signs of watering issues and or nutrition deficiency.
Red-brown spots are a more serious issue, and are likely a fungal or bacterial leaf spot.
You should keep the foliage dry and by pruning you can keep the leaves open to good air circulation.
When fertilizing make sure you use a special Bougainvillea fertilizer or a Hibiscus formulation.
Here are some links to refresh you on the care requirements.