The reason you don't want a tangled mess of roots on your transplants is that the slip develops it's sweet potatoes from the roots which go down, into the soil, from the new plant. You want those roots to GO DOWN and away from the slip, thus developing nicely shaped sweet potatoes. Stunting can also be a result. If you simply pop a started plant from a cup and plant it, roots and all, and if those roots are abundant and tangled, then you stand a good chance of getting gnarled sweet potatoes. I've had this happen when I finished planting my slips and decided to just plant my starter roots, which had grown an extensive network of thin roots in the pot or tray. The resulting harvest was smaller and it was misshapen. Here's a quote from Sandhill Preservation Center, and the link from which it came: "Do not think you need lots of roots on the slips when you plant them to be able to insure success. The more roots the more stress when transplanting and the more they will be stunted. The key when setting out the slips is to have very few roots and keep them as wet as possible in the garden for the first seven to ten days. Then back off on the water and they will go crazy. The worst possible thing you can do upon receipt of the slips is to pot them up and wait a few weeks and then transplant to the garden. You will have lost a good two weeks of positive growth and will have given them two chances to slow down. The more you slow them down, the less yield you have. The more times you transplant them, the more nonuniform roots and the less roots you will get." Here is a link that might be useful: Sandhill Preservation Center Sweet Potatoes

Yes, I forgot to mention that the water here is neutral to slightly acidic, and soft with low TDS. And humidity is high. Thank you, Kim, for adding the info. I'd like to add, about the issue of humidity. Besides misting or covering, perhaps having shorter cuttings put in tall cups might also help if the humidity in your area is not enough. Pictured below, I've tried taking very short cuttings (two leafy nodes) and placing them in 7-inch tall transparent cups. There's a hole drilled an inch from the bottom of each cup for overflow of excess water. I put this batch under full sun, with much success (in December, when the weather is nice and cool in Taiwan, any other time the cuttings would be fried under the subtropical full sun here I guess). As everyone says, hope you'll try different methods and good luck! :-) Hardy

But at least you can see anything that gets caught in them and clean them immediately b/f a major germ colony is established! It would also be a lot easier to spray w/lysol (if you like, I don't since it aggravates my asthma big time!) as you can easily get in the nooks & crannies w/o having to go into contortions to see underneath them, especially the bottom ones...which would probably have to be taken off to clean! And, trying to get all the PB&J from a cup pull would be just as trying as birdcage! See...it's all a matter of perspective and personal preference! [I wouldn't want to have to clean PB&J from either one! The solid/smooth knobs & bar-type pulls are probably the easiest to keep clean, if that's an issue for you.] Ours have not gotten dusty in the 7 months or so that they've been installed and only once did one get dirty (on the trash pullout), but it easily cleaned right up.

I will tell you how I do it, but be forewarned I have no idea if this is the proper way lol. I take the cutting, dip the fresh cut end in rooting hormone powder, then put it in a wet paper towel. Then I place that in a cup of dirt, and I slowly move up the container sizes if it works. I personally like to graft mine onto citation rootstock after its growing well. My neighbors and I root from cuttings frequently. How long has the branch been down?