In a blackberry smoothie, I don’t bother de-stemming. In a super light green juice or when I’m trying to be a bit sneaky with my greens, removing the stem can help cut any bitter or super pungent green flavor from the woody stem. If you are not using a high speed blender, removing the stem may also help you get that smooth and creamy smoothie.
Grasp the end of the stalk with one hand, with the other, lightly pinch around the stalk. Pull the stalk through the pinched fingers, removing the leaves as you go. Whala! I give the stalks to our chickens or the worms- or just compost.