2 cups packed spinach or lettuce (this is what makes it a "green" smoothie)
1-2 cups of other fruit
1-2 cups orange juice, water, or a combination
I prefer spinach or lettuce as the flavor is milder than other greens. I tried swiss chard at one point, but I found both the bitter taste and texture a bit off-putting in a smoothie.
I will often use 1 banana, 1 cup of berries, and 1 apple, cored and chopped into big chunks but with the skin still on as my fruit combination. I also buy big bags of frozen fruit to keep on hand for this.
If you use lighter colored fruits like peaches, mango, pineapple, etc. your smoothie will actually be a bright green color. Very fun!
I often add 1-2 TBSP of ground flax seed and wheat germ for added fiber and nutrients. My family REALLY does not like it when I do this. My husband describes it as "chewy". I get that, but especially if I just use the flax seed, it just seems like a few more berry seeds floating around. I think that the bit of texture is balanced by the huge nutrition boost. If I am sharing my smoothies, I make it without the grainy extras, pour theirs, then add in the rest and give it one more quick pulse to make mine just the way I want it.
My mom has added red bell pepper strips to her smoothies in the past and swears that you cant't taste it because they are pretty sweet. I can see this being particularly good in a strawberry smoothie.
Last summer we added cooked beets to our yogurt smoothies. I am sure they would work in green smoothies too!
I read somewhere (sorry, can't remember where) that someone added cooled green tea as their liquid. That would be another really good addition to increase the "power" of this drink.
Do you have any other tips or tricks for green smoothie making? Has anyone ever added yogurt to their green smoothies?