I've put a lot of effort into learning how to root kratom this summer. I've done side by side tests comparing several variables. I have a nearly 100% success now, and I'd like to share some of my findings. I think the most important thing is to have healthy, actively plants to cut limbs from. Secondly, you need to create the best environment. I use a large, clear Tupperware box with a heat mat under it. I pour in about 2 gallons of distilled water and submerge a bubble wand connected to an air pump from an aquarium store. Next I have a plastic grate that is about two inches or so above the water level. I take my cuttings and put them in a rockwool cube that has been soaked in distilled water, place them on the plastic grate, cover, and hang a 250CFL 2700K light about 18 inches above. Generally, I'll see some plants develop roots above the rockwool in less than two weeks. Between two and three weeks, they seem well rooted but many don't have exposed roots coming from the rockwool. I haven't tested the effects of pH intentionally, but they do well when the water bath is around 6.6. Temp of 83 degrees works well too. I've had success using dip and grow, honey (somebody said it works), Rootone, and no hormone at all. I've had success with a clean cut as well as with a nicked or otherwise damaged stem. I will say that Green Malay is a little harder to root. I've noticed when I express the liquid from the rockwool form any other strain (BB, PVI, Rifat) that the pH is 6.6, like the water bath. For some reason the GM is consistently higher, around 7.4. I think the real key is healthy growing limbs to cut, fairly aggressive lighting, pH 6.6 or a little lower, temp around 83, a constant flow of fresh air bubbling through water, and cleanliness to keep bugs and mold out. Also, don't think that you can't root smaller cuttings, I've rooted some that were three inches.