What sort of bloom fertilizer are you using? It doesn't have a higher % of Nitrogen than Phosphorus, does it? Three weeks is a bit long for it not to be showing any flowers. If you are already using a bloom fertilizer, make sure the plant isn't rootbound before upping the bloom fert dosage.

Might be a good idea to fill out the troubleshooting form at the top of the Plant Problems section. If there's something else ailing it, that info (along with pictures, preferably) will help to clear things up.