I bought a labeled mandevillia from (? can't remember)-- some nursery in Houston back in...like March. It has gotten HUGE and has gorgeous blooms all over, but NO trailing/climbing! It is situated in a pot, gets full sun and lots of water (1-2 times a day) and has a structure over it for climbing. Do some of the varieties not climb?
Can you post a picture of yours? There are some cultivars (the ones that were formerly in Dipladenia genus but have now been moved to Mandevilla) which tend to less viney than the ones that were always in Mandevilla so you may have one of those. Or maybe it was mislabeled and it's something else entirely.
It looks good and healthy despite the non-vining. If it makes you feel any better mine are still not vining and I bought them in full flower in April. Generally by mid August they've climbed and are full of blooms.
This just shows the difference between May and July but still no vining.
Pirl and ecrane, thanks to both! I just assumed all mandevilla screamed VINING! The one I had in this same pot with climbing structure vined like crazy but died last winter after giving with all its heart for 2 years. Texas weather...hmmmph! ;-)