It would be better to get the plants out of the cardboard cups before placing in the perlite. That’s really going to hamper root development and restrict moisture/nutrients getting from the reservoir to the roots.
I wondered if the cardboard might be bad for... biological reasons. But I'm a synthetic nutrients guy, for the most part, and tend to worry about rot and mold. Maybe those who go the "organic" route would consider such processes to be part of the cycle, IDK.
I don't like "grows roots through the container, just plant the entire thing" starter containers for garden-style plants, and always end up getting the containers falling-apart wet so that I can remove as much as possible before throwing the tomato plant (etc.) into a bucket of soil or the ground. I haven't done any in-ground gardening here for a couple years, but try to grow at least a few miscellaneous plants in containers and set up both in-ground and container plants for Mom at her house. I've never killed a plant by tearing the initial containers apart - even though I always see
some roots in the pile of crap that I toss in the corner of the yard to (presumably) compost/degrade.
Last year, I did two tomato plants in containers for Mom. The next day, she called to tell me that she had gone back after I left her house, and bought one more. I offered to come deal with it and she replied, "I watered it real good and planted it in the other container you prepared." (Guess she's not getting the jalapeño plant I was going to put in it, lol.) So, three plants of comparable size and the same variety... The ones I tore the "grows right through" off grew larger, faster.
But, again, that is with non-cannabis plants. I don't do that with them, primarily because we cannot pick them up at the local nursery here, lol. Therefore, I cannot speak to whether this little bit of stress would negatively affect them. Also, because I can buy
tomatoes in the store for a few dollars/pound.
Last year, I moved a young plant from a soil environment to a perlite one. I did what I've always done when I make the decision to go with a hydroponic method somewhat... late. Gently removed plant/soil from container, placed in a bowl of water that was ever so slightly warm - that, when I dipped my finger into, felt neither cool nor warm - and gently twirled/swished/plunged around in the water until much soil had fallen off the roots. I quickly grew bored with this (as per usual
), and proceeded to rinse and gently "work" the root mass (what there was of it) in my hands whilst holding it under cold running water. I was probably able to remove 95% of the soil - and ~15% of the root mass, heh - from the little plant. It was fine. Never produced an opposite-sex flower during its life. It was an autoflowering strain, and didn't appear to be stunted.
I don't consider myself to be a "master-level cannabis grower" (LMFAO), so I cannot say, "Do it this way! You will be
fine." Rather, I'm just recounting my experience.
I stopped using those expandable discs covered in a flimsy mesh (Jiffy? Don't even remember...) back in 2006 or 2007. Place I was working at had one of the countertop display boxes. They were inexpensive, the owner of the store let us buy whatever we wanted at her cost, so I bought a small poke full. Took them home that evening and saw tiny whitish critters crawling on them. Slowly moving dots. Into the garbage can they went. I don't suppose they were any kind of root maggot, because there are no roots in the dry, compressed discs. But I didn't want to take any chances. I've been wanting to try those newfangled ones, but they don't seem to be sold in stores in my little city.
I'm just... rambling.