they need plenty of water in hot weather or they wilt very quickly, what else would you like to know?

Frequent, light feedings, or a timed release plant food. Also will probably need some shade on Malta, from what I know. We give them complete shade here in the American desert, but they may only need afternoon shade there. If they were blue when you bought them, they may only be blue again if you grow them in pots and use an acid-forming plant food. Limey soil or water makes them turn pink or purple. And, as Pam says, ample water!