Rangoon creeper or quisqualis, hides its seeds under leaves after all blooming is done in the fall, you have to search for them, but do not pull them off while green. Wait until they are brown. If a seed falls in fertile soil it will sprout but I dont know how long they take. In the past I sowed them in pots and had no luck so I decided to crack the seeds a little, (do not crack the seed completely open) and Eureka!, they sprouted in about 30 days. I gave some little plants away and they died (or got killed) so maybe they dont like transplanting.
About invasiveness, let me tell you that they come up in a lot of unexpected places, and they seem to be growing underground from the mother plant, the roots go all the way to China. I pull them out and they come back. I place a heavy paver on top and they sneak around the edge of the paver and come back. Very persistent!
The other problem is pruning because of the spines, but since quisqualis drops most of its leaves in the winter it's easy to prune the undesired branches then, when you can see the spines.
By the way dont worry about the maroon color of the leaves in winter. Its OK.
In spring it will get green again. Happy gardening!