I tried bag rooting in Phoenix AZ Spring, Summer and Fall using cactus mix, which is what we commonly use to pot root. All of the cuttings rotted. I just couldn’t make the cactus mix work. I got over my fear of the hydroponic store and opened my mind and was very pleased with the results. Last year I rooted over 100 cuttings in Winter inside on a heat mat. I ONLY USE COIR for bag rooting. (Coir + perlite also works, but in my experience, this is just as easy.)
Get a block of coir. Moisten it with plenty of warm water. Some say you can squeeze out the excess water, but I prefer to break up all the clumps and make it uniform and just let it dry out for a couple of days. In Arizona it dries out quick! You want it so it does not adhere to your hand at all. If it sticks to your hand it is too moist. If you pack it in to a baggie, and insert a water meter, your water meter should read 1, 2 or 3. (On a scale of 10 where 10 is completely saturated.) Too moist coir will rot your cuttings. Too dry might not root them, but it won’t rot them either!
Prepare your cutting. I have better luck with a straight cut. I sometimes use rooting hormone, but do not think it is necessary.
I like to use disposable baby bottle liners. There is an 8-10 oz size that is perfect. I cut the hard plastic ring at the top off, and I pack the coir in. You can compress it with a lot of pressure or a little, just don’t leave it super fluffy. Add your cutting then pack in some more coir. Seal with electrical tape or a zip tie.
I place my cuttings on a pan on my heat mat. I have a 48″ by 20″ heat mat that fits perfectly on top of a shelf from Costco. It can fit four large catering trays. You want your cuttings to remain upright.
The room I root in is very warm with indirect light. The light does not matter. It could be dark. It is the constant warmth that helps them root quickly.
The baby bottle liners are great because you can see the roots, and when enough grow and harden, the bag can be cut off leaving a solid mass of roots and coir that can be planted directly into coir or your preferred soil mix.
Some large cuttings, white or yellows, or fast-rooting varieties can root in under a month. Red, 8-10 inch cuttings, older cuttings, and greener growth may take longer to root.