There are as many different mediums and various mixes as there are people to talk about it! The main thing to consider when choosing a rooting medium is “will it or the chemicals I supply, make an hospitable environment to grow in”. That is the six million-dollar question. The cutting wants; pure pH 6.2 water, root oxygen, weak food, CO2 and low levels of light. It wants this delivered in quantity when it wants it too. Here are a list of the more common rooting mediums and the pros and cons of each.
Peat Moss
Is organic so the pH is of low priority because organic mediums provide a pH buffer for the plant, it also holds water well in small quantity. In large quantity it provides something like Perlite to increase drainage. Drowning is the biggest concern. You may also need to add oxygen to the food.
Sand
Is natural, but it has no pH buffer, do a pH check on some of the water that has sat over night with sand in it to see if your stock of sand needs pH help. Sand doesn’t hold water well although it does drain well. You will need a frequent watering schedule for sand. Wash sand well so the fine particles can’t plug up the cutting as it takes water. Sand has an almost ideal although temporary climate to root in.
Perlite
Is a synthetic and requires a pH test and help to correct to 6.2 it also has no nutrient so you will have to supply food. Perlite is also a very loose medium offering minimal support to the stalk. For those who want to get a clone with just roots, Perlite washes out with minimal damage to the roots. Actually the stuff doesn”t hold together at all. Perlite is white and floats. Perlite is great for root oxygen. Perlite doesn’t hold water well although it does drain well. You will need to water often. Perlite is single beads of Styrofoam.
Vermiculite
Is a natural medium but still requires pH testing due to the mineral content. Vermiculite drams well and provides a bit of water retention as well! There is plenty of air to oxygenate the roots too. Vermiculite is Mica that has been superheated until it pops into flakes like popcorn. When cool it has zillions of micro fissures in the flake that holds the water.
Rockwool
Is natural but it needs some serious help with pH. Soak Rockwool in pH 4.5 for 24 hours from dry before use. The problem is that over time the core of the Rockwool will alter the pH considerably. Water the Rockwool from the top so the nutrients in the block are exchanged. Rockwool has excellent drainage and keeps an ideal environment for propagation.
Professional Potting Soil
Is organic and is usually peat moss based. This stuff combines the best of the organic worlds to create an excellent rooting medium. Usually the only problem is if the medium is saturated with water or if you add food to the water. Most potting soils contain an initial charge of fertilizer to get the plants going. They also will hold too much water for propagation, drain extremely well and squeeze out as much as you can of the moisture with your hands.