Nope, you can throw the whole thing right in. The stems shouldn't add any bitterness at all. Some fruits and veggies you'll want to skin or leave greens out (Apple seeds & carrots have toxic seeds & leafy portions respectively but they're rather low levels for human consumption) but most of them you can just toss it all right in the juicer. Some even have good nutritional value in the parts you don't generally eat. Some can be bitter though but kale isn't one of them that I'm aware of unless you got a hold of some bad kale.
Hmm, I didn't core the apples, just cut 'em in half and in they went. Might have been the cucumber, lemon or ginger too, although I did peel the lemon. Ginger just went right in. Gotta get a recipe book or two, I can see it already.
There's a lot more of us ugly mf'ers out here than there are of you pretty people!
- Frank Zappa
Scrotum Diem - bag the day!
It's all shits and giggles until someone giggles and shits.....