blooming white flowers and red flowers how did that happen
This is typical of multicolored cultivars, like "Sundaville" so it could be possible that, while it appeared to be white, was only showing white flowers at the time.
My other thought would be that another seed made it into your pot and was not flowering until recently.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla
I have had mine a few years and it’s gets full sun and has lots of flowers the entire summer. It has never had seed pods and I am wondering which ones I should look for that do.
It is very easy to miss the seed pods. They can resemble twigs, or fat stems, or bean pods, and contain very small and hairy seeds. (They kind of remind me of milkweed or dandelion a bit.) Cutting off spent blooms will remove potential seed pods. Potassium can help with seed formation, but make sure that the soil does not have plenty, already.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-propagation.htm
Does this require full sun, partial sun or shade? How can I keep it over the winter?
This series of articles will have everything you need to answer your questions about Mandevilla.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla
Both planted withing 5 feet of the other. same soil mixture, sunlight and fertilizer - Miracle Gro. Mostly sun with some shade in aafternoons. Both climbing nicely but no flowers/blooms on the white one.
This article should help:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/getting-mandevilla-to-bloom.htm
Unfortunately, this might be a complex issue that I am not able to offer much assistance on. If it comes down to it, you may need to sacrifice shade, or accessibility.
Otherwise, a different plant that stays evergreen could be an option!
https://www.gardeningknowhow.com/ornamental/vines/ovgen/creating-shade-with-vines.htm
https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-6/zone-6-evergreen-vines.htm
I don’t have any
th how much water. Please advise
That will get you about 1/4 of a gallon in my experience! You can use between 1-2 tablespoons per gallon, depending on the results of your soil test.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/epsom-salt-gardening.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/test-soil-for-pests-and-diseases.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/making-sure-soil-drains-well.htm