-No ferts at all to start
-Unless you are going into hydro, and even then, rockwool may not be the best choice for seeds. I find it difficult to work with, and prefer unferted soilless mix or rapidrooters for seedlings.

How large are the cubes? If you started in the little plugs or 1 1/2" cubes (coorect size for seeds), you should definitely see roots by now.
stinkyattic Reviewed by stinkyattic on . Where's my roots???? Hey all! After taking a nice 10 year hiatus from growing, I am realizing that I have forgotten way more that I realized (wonder how that happened?). Long story, short. I have planted seeds into rockwool cubes exactly 16 days ago. I have nice little sprouts, but there isn't any sign of roots starting to protrude from the rockwool. The cubes have been kept moist, but not wet with 1/3 strength solution and are in a dome to keep the humidity up. The spouts look great, but no roots. Rating: 5