Gardenias gone yellow.

Hi could anyone help my sister in law who lives in southern spain? Her gardenia buds have gone yellow and don`t look like they will bloom. :( The plant itself looks healthy with a good cover of leaves. Any ideas?

 

Not had much experience of growing gardenias in Spain I'm afraid pip.
But at a guess could it be dry at the roots, how long has it been planted?
Is it a well established bush?

 

Bought as a young bush 6 months ago and it is currently sat on the roof terrace in a container. As regards the dry roots, it`s rained quite a lot these past few weeks. I thought the buds might react like rosebuds do after a soaking and then rapid drying off in a strong warm sun, they shrink and don`t open at all.

 

Possible I suppose, but my money's on dry roots, rain doesn't get into containers very well, is it in erecaceous compost?

 

I dont`t know what compost she has used but I am visiting next week and I will find out more, take some pictures also