Mandevilla laxa is also distinguished by its succulent, subterranean caudex.
From the sfgate.com
If you want a caudex, you must grow the desert rose from seed.
From the dailynews.com
A swollen trunk or root at the ground level of a plant is called a caudex and plants with swollen bases are called caudiciforms.
From the en.wikipedia.org
You can propagate the desert rose from cuttings but such cloned plants will be without the telltale caudex or swollen trunk that is part of the plant's personality.