I'm not a gardening expert myself but yes they should grow excellent in Houston. They love moisture and heat though prefer some shade. As far as timing, I start mine in the house and then transplant outside when they have at least 3 leaves. In fact it's better to plant shrubs and trees in the fall, so u have plenty of time to start these cause they're not going to grow overnight in your garden but when they DO grow, they're beautiful ;). You can find tons of info online about how best to grow them and any helpful hints too :). G'luck!
Fanned and Bidding!!! I desperately want to start some gardenias for my balconies to go in these big beautiful urns that are for trees! My mother wore the fragrance 'Jungle Gardenia' when I was a child and it brings back so many memories! These will be moved inside during the winter to my foyer so they stay warm and sunny, and I am so excited at the prospect of smelling them all summer long!!!