If, like me, you kill plants with ease, then I'd recommend becoming best friends with your florist. Here are my favourites around our sunny little island:

Fleurapy

Pauline is without a doubt one of the most creative florists you'll find. She once made a birthday cake, all out of flowers, for a friend of mine, and her creations never fail to surprise and delight. Call her, brief her and prepare to be blown away.

http://www.fleurapy.com/

JiMei

If you've got a knack for arranging, then the flower market is your best bet, and this particular flower market (which has been around a long time) boasts one of the most impressive cold rooms in Singapore - and it's always stocked with a variety of seasonal and staple flowers. Need a special order? Or a specific type in bulk? They'll do that for you too. 

https://sites.google.com/site/jmcomsg/