Six feet tall isn't big enough to bloom, Zambujal. It also isn't very big for a 5 year old Jacaranda, either! Normally, a healthy young Jacaranda will grow around 3 feet a year. I would feed it something like rose food--8-10-6 proportions--three times a year, to get some growth on it, and to promote early maturity. If it is small due to frequent freezing back, every time it freezes, it will set back the clock. It may have been blooming when you bought it because growing it in a container will cause it to mature early. Once planted in the ground, it will usually grow at least 15 feet tall before trying to bloom again.

I was in the Canaries recently and the streets were lined with Jacarandas, 20 to 25 feet tall and full of bloom they were beautiful, so patience is needed as Tug. says!