Willow Bark Extract ( very weak - aspirin ) is good for toughing up the plants immune system mostly - known as the SAR response . Some extra root growth happens regardless of how started, as long as the plant is still in the veg. stage. Seaweed extracts are very good for plants in veg., boost vigor, increase root mass and help keep plants on the shorter / wider side. I prefer seaweed over all others. Like quoted above it shifts the ratio of auxins to a more veggie side of the force.
Johnny-come-lately products like Bush Master (Humbolt Co.), that are way over priced are just seawead extracts at double strength - like Liquid Karma (great stuff) - is mostly unsulphured molasses. Both will drain your wallet, fast, both can be equaled with cheaper substitutes - like at Wormsway (
www.wormsway.com) plenty of cheaper alternatives there, or search for Organic Fertilizer or Organic Tonic (Ebay) - if you find any made by Blue Mountain Organics - buy it. It's cheap & totally kicks...*ss..... The mychorrizal fungi in that stuff, will cause a plant in a 55 gallon barrel to get root bound.... Amazing - Hippie - Organics... & it's cheap..... Just proving more expensive is not always better....