in Texas when is best time to plant nasturtium seeds?
You will want to do this during early spring. This will give them plenty of time to flower before it gets too hot. I fear it would still be too cold in your area in the late winter for them to grow year round. You are right on the line between them being able to survive and not. Here is an article for more information on their care: https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm