Originally Posted by 75north

When it gets a little bigger (about a foot tall) you can tell by the shape of the leaves. If they start out long and thin and "sword-like" then it's (obviously) a sword sucker. Big, wide leaves on a small pup and it's a water sucker.

Sword suckers have much better root systems supporting them, and so if you separated a sword and a water sucker and planted them side-by-side the sword pup would grow faster will often produce a bigger bunch the first time around.