@Hetty, I don't know about how it would look. One idea is an earth with the center latitudes bulging or glowing? Or, just an icon for people who don't have to deal with cold as a factor in planting, perhaps a circle with a slash over a snowdrop? Although I don't really like being defined by what we are not rather than what we are.
I would buy a Mexico icon but I might be the only one
The flag is red, white and green with the eagle holding a snake in the center, Independence day in Mexico is coming up soon, Sept 16th, so it is a good time.