This is the first bloom from the second of the five seeds I bought on e-bay. A very pleasant surprise

Pink? Salmon? Very pretty either way.
Meanwhile the first one is blooming insanely.
Need some advice. It's starting to get cool at night now (low 50's). I don't want to lose any buds and future blooms. This guy is coming inside for the winter. What's the coldest he can take before he starts to drop buds?