There's a nice voronoi node on gumroad somewhere that some of our foliage artists have used to great effect. alternatively you could look at igor elovikov's nodes which shuld allow you to create the same sort of effect
What you're asking for is the same problem as growing trees or cracks. It's possible to do implement in designer but it is a truly obnoxious endeavour. fx-maps are the easiest way to handle recursion but you are very limited in terms of blending. Pixel processors are basically the opposite