Maybe this is too obvious, but does being in a cold, dry incubator for 7 years affect plant growth?

Given the fact that, say, expert cherry tree watchers in D.C. still mostly guesstimate as to when a given tree will flower from year to year and whether it will “peak” with its fellows, I’m not sure we can assume that different flowering times in different samples automatically means “climate change induced evolution.” Now if one batch of mustard plants is throwing little spears at the other one, you might be on to something.