I've been drinking green smoothies in the morning, and I've thrown zucchini, peas, cucumbers, spinach, kale, swiss chard, arugula, romaine lettuce, and bok choi in there.
While I wouldn't feel like eating these green vegetables on their own in the morning (especially not raw), I do like them in smoothies. I think it's cause I add some fruit (tasty, sweet ;-) ) and because the blender really breaks down the tough parts, so my teeth and stomach have less work to do.
For some reason, I don't really have an appetite for green smoothies at night. Maybe having a "warm dinner" is too ingrained in me...
But anyways, upping the "green intake" really worked for me when I started drinking green smoothies. Dust off your blender and try it :-)