Question
I live in Maldives (south of Perth) and have three gardenias in my front garden.   They are about to flower even though the plants are pretty paultry.  They have yellowing leaves and not much foliage.

How do I care for these plants.

Answer
Dear Daphne,

Hello there, my name is "Coach Dave" and I work for The Home Depot. We are a "boomer" of a home improvement center in the USA and a few other countries. In regards to Gardenia shrubs, let's see what we can figure out.
Gardenia shrubs come in over 250 species. I would guess by your location that you have a heat tolerant variety, however this still is a guess.

The first thing to do is to make sure they have proper amount of nitrogen. A high acidic slow release fertilizer rated for "acid loving plants" is what you are looking for.

When there are no blooms in sight it is time to trim off dead or dying branches. This keeps the plants energy focused on blooming and new leaves.

Gardenia's like shade and indirect light as much as possible. Sometimes they need to be relocated to keep them happy.

The soil should have peat moss, mulch, or other type of organic matter to keep the soil soft. There are many types of Azalea and Camellia soils available that can do a great job for this. I like to add used coffee grounds every chance I get to keep my Gardenias leaves green and waxy, this is a real treat for them.

I hope this answers all your questions, if you still have more questions let me know, I'm here to help.

Yours Respectfully,
Coach Dave