Sweep NURBS from Dynamic Spline problem

Hi,
I'm trying to animate with dynamics kind of algae/seaweed/tentacles etc., fixed from the bottom and swinging in the air.

I tried with Spline Dynamics (with a Constraint Tag at the bottom) inside a Sweep NURBS but the base of NURBS is rotating on itself along the Y axis, not "rooted" to the ground.
The same happens if I use a Spline Wrap deformer referencing the Dynamic Spline.
This is NOT happening with the Hair Object, the guides are rooted in the ground, but the problem with this is that then I can generate just instances of singles meshes and not complex objects, e.g. nested or animated.

Thank you

Corrado Carlevaro