Jacaranda is a single trunk tree. What you have sounds like the original tree died and you've got a bunch of "suckers" coming up from its root system. Your best bet would be to select the tallest and thickest of the suckers and cut the rest of them off. However, you could choose three of the suckers and let it grow into a triple-trunked Jacaranda, which would be quite interesting in 15 or 20 years.

We had a jacaranda tree in Phx,AZ (pretty much a 9b where we lived) and it did okay even with a few light freezes. It was pretty huge. I have 3 sausage trees here in zone 9a FL. I usually put them in the gh for the winter and sometimes they drop their leaves but leaf back out in the spring. I left one out last winter in the ground as an experiment and when it dipped a under freezing, it froze to the ground but it eventually came back up this spring and has 2 trunks now lol. I had thought it was a goner. I am gonna dig it up again this winter. I covered it the one time we dipped to 32F this winter and it will be 34 tonight so I will just cover it again. If it looks like it will get under 32F I will have to dig it up and move it into the gh.

I have a new jacaranda tree. It has been in my yard one year and I bought it from the local nursery when it was one or two years old. So o think it's either 2 or 3 years old. At the most I think 4 years old (guessing). I don't see any branches, it's just a straight shot up about 7 to 8 ft. It does grow the green branches from the top of the tree but is there a certain point when actual wood branches will start to grow as offshoots from the main trunk? See photo:

it sure doesnt look good to me.. but what do you have to lose ... make sure you plant it at the proper depth ... so that the root flare is at soil level .. https://duckduckgo.com/?q=root+flare&t=ffcm&iax=1&ia=images the fact that i see no root flare ... and it has those problems at the soil level.. is why i wonder about its odds of success ... also.. just fyi.. 100 degree temps were not as bad as a black pot in sun.. which could have easily heated the roots over 100 .. and roots dont like that kind of heat ... try to store pots so the pot is shaded.. and the plant is in sun ... if you can ... or better yet.. just get it planted .. but heck.. life gets in the way.. i know ... good luck ken