Hi Mary Jane.  Thanks for contacting the Extension Master Gardener Helpline.
I think the plant you've photoed is a Mandevilla, possibly Mandevilla sanderi but I'm not sure.  It's a very big genus with tons of hybrids/varieties/cultivars.
That identification comes with a huge caveat:  you say it's in an old garden but you don't say where or what zone or how it's being grown (in the ground?  in a pot?).  Mandevillas are tropical plants and usually planted permanently outdoors only in Zone 9 or above.  Here in Vermont (Zones 3-5), they are grown in pots outdoors in the summer and in a heated greenhouse or sunny window in the winter.  I've seen them used in a lot of Vermont gardens as annuals, i.e., they are planted for just one season and nurseries usually put them with their annuals for that reason.

Here is some more information:

https://plants.ces.ncsu.edu/plants/mandevilla-sanderi/

I hope this information is helpful.  It's a beautiful plant when in full bloom.  Its cousin, Mandevilla laxa is a deliciously fragrant vine.

Jessie, Extension Master Gardener Helpline Volunteer

Hi Mary Jane. Thanks for contacting the Extension Master Gardener Helpline.
I think the plant you've photoed is a Mandevilla, possibly Mandevilla sanderi but I'm not sure. It's a very big genus with tons of hybrids/varieties/cultivars.
That identification comes with a huge caveat: you say it's in an old garden but you don't say where or what zone or how it's being grown (in the ground? in a pot?). Mandevillas are tropical plants and usually planted permanently outdoors only in Zone 9 or above. Here in Vermont (Zones 3-5), they are grown in pots outdoors in the summer and in a heated greenhouse or sunny window in the winter. I've seen them used in a lot of Vermont gardens as annuals, i.e., they are planted for just one season and nurseries usually put them with their annuals for that reason.

Here is some more information:

https://plants.ces.ncsu.edu/plants/mandevilla-sanderi/

I hope this information is helpful. It's a beautiful plant when in full bloom. Its cousin, Mandevilla laxa is a deliciously fragrant vine.

Jessie, Extension Master Gardener Helpline Volunteer