Tropical Zone Gardening: Hydrangeas in the tropics , 1 by ardesia

ardesia wrote:
Your statement about the stems "growing very long" might indicate there is not enough light. Hydrangeas do not like full sun in the warmer climates but they will not bloom well in full shade either. They need dappled light or the stems will elongate reaching for the sun.

We don't know which variety of Hydrangea Lsp has; so many of the newer varieties bloom on new wood which makes them ever blooming in the right conditions and they can be pruned any time. Maybe you can identify which variety you have by checking with a nursery.

Make sure there is plenty of air circulation, they get fungal diseases easily in our humidity so it might be an issue in Malaysia also.

Which zones we live in only seems to serve as a guideline. I am in the same zone as the Pacific Northwest yet our climates and growing conditions could not be more different.