Hi Russell, That looks like an interesting tree. According to
The Ferns Muntingia calabura is a pretty tough cookie, thriving in most soils. I would suggest giving it a really good soaking when planted, assuming it has a pretty large planting hole, and again maybe once a week for a month or 6 weeks. Hopefully the
roots will then be growing into the surrounding soil and it
should be OK. If you get no rain for a few weeks, then it may be worth topping it up again, depending on your temperature. I'm only guessing here on your climate. It's better to water a lot but infrequently if possible to encourage deeper roots in general.