plus regular summer watering. Mulching around the roots with organic material (eg, compost, straw, bark, etc) will help to retain soil moisture in summer, but only apply the mulch over moist ground, not over dry ground, otherwise the mulch might prevent rain reaching the soil. A thickness of no more than 50mm of mulch is recommended.
While jacarandas can be grown from seed, their flower colour varies more and they take longer to flower, but as seedlings often pop up around the base of trees, transplanting them is worth a try and doesn’t cost a cent.
Don’t prune them!
Forget about pruning jacarandas altogether or you will spoil their good looks, and the tree’s shape, forever. When you prune a jacaranda it then sends up vertical shoots (you’ll often see the effect on jacaranda street trees which have been pruned to make room for overhead powerlines). The normal shape for a jacaranda is that of an elegant umbrella, and the appearance of vertical branches ruins its good looks. Your only solution, if you have pruned a jacaranda, is to persist in cutting off the vertical shoots.