They grow straight up and then at some point (I'll have to pay more attention next year when the seedlings sprout) they fall over from their own weight, the main stem is small (about a 1/2-inch at the base) for the length the plant attains, which is at least 5 ft long (but probably longer). When they fall they get tangled up in whatever is around, due to the numerous small (very fragile) branches. That's another thing I want to do next year is provide some type of support and see how tall it gets, but I can see it being easily broken just from the wind, since the stem is fragile.
The result is that the plant looks like a small bush, but it's just a bunch of plants that are tangled up together and there's no real way of untangling them without severe damage to the plant(s).