Bonsai trees, in general, require more attention than your standard every day house plant. The soil needs to be kept moist (but not wet) at all times. Bonsai can very easily die due to over watering. On the other hand, bonsai root systems are much smaller and can easily dry out if not kept moist. So you can see it is a delicate balance that you need to juggle. The gardenia is hardy in zones 7-9 so your bonsai can be grown outdoors in some places around the country. Remember, you bonsai will still need a good deal of attention even though it is growing outside.