I get fabulous roots under 24h.
Your root vigor is largely dependent upon soil lightness and oxygenation.
I recently did a test where I put newly-rooted clones in rapidrooters into party cups full of very light compost/perlite mix. The roots hit the sides of the cups in 2 days under 24h light. No complaints here!
stinkyattic Reviewed by stinkyattic on . vegging who has tried both th 18/6 and 24hr veg cycle?which best ,,what diferences are there? doesnt the 24hr stress the plants? can u use 24hr straight from seedling? Rating: 5