Potted climbing plant is dying - any suggestions?

I’m not sure. If it is because of over-watering due to excessive rain, which seems logical as many plants will experience root rot under this condition, you would want to dry the soil out by not watering for a while, keeping rain out, and hopefully setting the pot under some serious sunlight. Alternatively, you could basically replant it in new soil. If you get a lot of rain, or if you have a very clayey soil, you might want to consider mixing the soil with some kind of rock or other aggregate or even potting soil to get better drainage.

This site says excessive water will lead to root rot.

I’ve taken a plant out of the soil and washed the roots off with lukewarm water, then replanted. This was recommended by some forgotten plant person. Can you make holes in the bottom of your pot?

sounds like overwatering to me.

Crappy Soil- repot and save your baby!

Re-potting several months ago may have been not advisable because of weather and seasonal change, any replanting/potting should be done in January when things are hibernating. If the location is sunny and the pot is movable to a shady spot then this should be done as soon as possible, then the odd thing is Water water water to saturate and prepare for a removal from the planter. The watering fills the plant and suspends it so it has less shock after being messed with, then remove from the pot and if the root ball has caked soil on it dunk in a bucket. Keep it under water and carefully remove the soil considered a full repotting procedure. Go to the nursery and get an soil mixture that is Not a potting mix with all the peralite white stuff, you want a mixture that has sand and forest humus and be sure to test it- most mixes have clay that is currently killing your friend because when you water it forces out the air then the plant droops from Overwatering.

test the mix by wetting a handful and squeezing then tapping and it should fall gently apart but be like a sponge, then put some in the bottom of the pot and saturate then put the plant in then add soil compressing softly with a closed fist. half way up water again and continue untill done and then water filling the top three times. on the third then wait thirty minutes and check like it is a cake using a long knife or skewer and it should come out moist, then dig a little and all should be moist like when you tested the soil when you purchased it.

Keep in shady spot for at least this summer and feed and if there are any flowers Remove them so the energy goes to the roots, check stems even if they are bare bending slightly and if pliable they are Alive!

I’m no botanist by any means so I take no responsibility for your plant’s future… That having been said: I have a Mandevilla in a pot as well. The pot is about 12 inches in diameter (at the top). I leave it out in the morning sun because I live in Texas (it’s 100 degrees everyday). It’s been poured on several times and seems to keep thriving. I wouldn’t recommend repotting at this point because you just recently repotted and I think that will cause more damage. I would try to just keep it dry. You could also try blow drying (probably on a cool temperature) the top of the soil and that might dehydrate it a bit.

According to this, it sounds like the full sun is not the problem, but the overwatering probably is.

An important “how to” in mandavilla care is to use a well drained soil as these plants can be very sensitive to over watering. Allow plants to dry between waterings. When you water, make sure you water thoroughly. Remember to water SLOWLY so all of the soil gets wet.