To echo Jakedatc, save the static stretching for after the ride. Static stretching (going into a stretch and holding it for 30+ seconds) does help increase flexibility long-term, but has been shown to leave the muscles slightly weaker and less responsive for about 30 minutes post-stretch. If you just generally feel better after doing a good stretch, and prefer to start a ride off that way, there's no harm in it, just as long as you're not going to go full-gas right away, but it's not the most useful thing to do pre-ride.

However, dynamic stretching (continually moving through your range of motion) can be a good pre-ride warm up. Think along the lines of stepping back and forth quickly from one foot to the other, while kicking your heel of the free leg up towards your butt (dynamic stretching of your quads) or doing a goose-step sort of march around, swinging your leg up in front of you with each step (dynamic stretching of the hamstrings). If done with ease--not excessive force--this moves your muscles through their range of motion and helps get blood flowing through them, starting the process of warming up the muscles. Or just hop on the bike and ride, slowly amping up the effort as you warm up.

(FYI, in real life I teach ballet, and have spent a lot of time researching--and practicing--best stretching methodologies.)