I have had white flowered Mandevillas for three years running. At the start of each winter, I move them into my spare room, which is kept fairly cool. They stay green and healthy (though not flowering) throughout the winter, and then in February, the leaves drop off and the plant dies.
Last summer, I bought a pink flowered Mandevilla from my local supermarket (for £2.50!) I treated it the same way. It sailed through the 'February death moment' without dropping a single leaf and is now sitting on my patio, bursting with health, and just about to start flowering. The white one, which was a couple of feet away from it, died in February as usual.
What am I doing wrong? And why has the pink one survived when the white ones don't? I much prefer the white ones, so I'm really gutted that I keep losing them!
I'm living in South Wales, UK, near the border with England. In winter, the mandevillas are in a west facing room, minimum temp would be around 10C.
Can anyone help? I really want to buy another white one this summer (assuming lockdown ever lifts) but right now, I'd feel like I'd be condemning it to an early death! Please help