Question
Hello,

It looks like my King Sundew has started sending up some sprouts from a part of the root, and I was wondering how large they should get before I can separate them from the main plant?

Answer
This entire depends on the main plant.  If the main plant is young, then you need to wait until the plant is significantly larger before attempting to separate them.  If the main plant is mature, then you should wait until the plantlet is at least a quarter of the size of the main plant.  

Separating the plants, however, requires cutting the roots.  You'll need to make sure the plantlet has sufficient roots to sustain itself when it's cut from the main plant.  

For examples on how to do root cuttings, watch Volume 2 of the Grow Carnivorous Plants DVD series.
http://www.cobraplant.com/dvd

Good growing!
Jacob Farin