Isophenes

[nightshade]

I came across the word Isophenes today,which are apparently imaginary lines
which follow the progression of spring flowering across the country northwards at an estimated 2mph walking pace do you think that this pace has altered much due to the global warming?

[StuartDH]

Sounds like that's the same sort of thing that was on Countryfile the other week, where some farmers with enormous combines travel up the US to harvest the crops. Starting in Texas, they slowly make their way up to the Canadian border over the course of a few months, and harvest fields along the way.