The formation of roots is controlled by the change in hormone balance at the base of the cutting now that it is not receiving anything from the mother plant. Using a hormone rooting powder can speed this up and the quicker the roots form the better. The speed of rooting is also considerably affected by temperature. The range at which cuttings will root is from about 14°C to 25°C (58 to 78°F) but 20°C (68°F) at the roots is ideal. The air temperature can, however, be much lower as is often the case if soil heating cables are being used.
The compost is only required initially to hold the plant in an upright position and provide plenty of oxygen where the roots are forming, with perhaps a small amount of food. There are any number of mixes that can be used, the emphasis being on the right particle size to prevent water logging, but the best way is to buy it already made up as one of the proprietary rooting composts.
So to obtain good rooting all that is required is a small pot or box of rooting compost kept at 20°C (68°F) in a moist atmosphere or with a plastic cover over it. The time of rooting is not critical but the beginning of March is about right for most general varieties. When the cutting begins to root it will be noticeable that the leaves wilt less and that by the time it is ready to be transferred it should be just starting to grow away.
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