Recently, I've been making 100% fruit smoothies for my family. They've been a hit, but I'm thinking I'd like to hide some veggies in there. What, if any, veggies can I hide in the smoothies without drastically affecting the texture or taste?

Much of the fruit in mine are frozen, so they're very cold. In fact, I've taken to mixing them a little a half hour before serving time, then letting the frozen fruits soften a little in the blender. Then, at serving time, I blend it all again. I don't know if this will make a difference in your answers.

And, so far, I haven't had to store any smoothie longer than overnight, but I was thinking of making up a bunch, then storing it in one of those mixing pitchers so I can more easily have some during the day or whenever. I know adding lemon juice will help preserve it, but for how long? How much lemon juice? Is it just going to look icky after 24 hours?

Spinach and mixed baby greens are good (but color it strongly). Cooked pumpkin, squash, carrot and the like are sweetish and good.

Just wanted to add that you CAN store smoothies but they DO separate though and begin to lose active enzyme status when stored.

sweet potatoes!

I bet avocados would blend into smoothies well and they are a superfood. You want to use ones that are on the ripe side (the softer they are, the better they will blend) and you'd want to go a little easy on them because they are very high in fat (even though it's good fat).

Also, I bet you could successfully hide some peeled eggplant in a smoothie without it making a noticeable change in texture or taste (eggplant is pretty benign).

Also, silken tofu would probably blend in well and is great nutritionally. Tofu is made from soybeans, so that counts as a veggie in my book. If you can't find silken tofu (it will say "silken" on the label), you could try soft tofu. But I think the silken would work best.

I've managed to successfully use pumpkin, spinach, cannellini beans and steamed carrots in smoothies. Spinach with strawberries worked well - and with the pumpkin I used orange and cinnamon. The beans, provided you don't go overboard, worked well with almost anything - the cannellini beans are pretty neutral. It will taste "beany" if you add too many, though! Trying to sort of "match" flavors seems to work better than just tossing everything in!

Silken tofu whips up beautifully in a smoothie, and wheatgrass is something else that works with most flavors. I can find it at my local health food store, but don't know how easy it is to find generally?

A powerful blender is helpful - I started another thread about my Vita-Mix, which is awesome. In it, everything gets blended really well - no chunks or spinach bits floating around. Even the little seeds on strawberries or raspberries get completely pulverized so everything is nice and smooth - pulp from oranges, too. I've had luck with my smoothies staying nicely emulsified for a good couple of hours after being blended, but have never tried to keep them longer. My personal opinion is that they're better fresh, especially since they take very little time to make. Maybe it would be easier to have all the fruits/veggies prepped in advance, so when the urge stirikes all you have to do is toss everything into the blender? That would save a fair bit of time.

In latin america they often blend avocado into shakes and smoothies and they taste awesome, with a creamy silky texture. (learned this during a homeschool project last year)

Also what I have done (don't know what equipment you have) is to juice some veggies and put them in smoothies. I found that some spinach, peppers and carrots in smaller amounts can be slipped into a smoothie easily. Just an idea.