A stem cutting is made by slicing off a section of stem, roughly four to five inches long, with a diagonal cut made just below a leaf node. If the plant from which you are making the cuttings is overgrown you of course can make a number of cuttings from it. The slips, as the cuttings are called, should always be made with a sharp knife or razor blade and never with a scissors, as a scissor will crush the stem and the bruised fibers will tend to rot. The cut is always made diagonally to expose as much rooting surface as possible. If there are any buds or a great many leaves on a slip, they should be cut off as they will retard the rooting process.
Fill however many pots you need with the starting mixture and with a dibble or pencil make a hole for each slip you want to insert. Place the slips in the holes and press the soil around the stem. Slips should never be forced into the soil as this will cause them to bruise and then to rot; you should make certain, however, that the end of the slip is at the bottom of the hole and in contact with the mixture or it will not root. Once the slips are “planted” the pots should be given a complete soaking, either from above or below, and the slips should be covered with an inverted glass or mason jar, as illustrated. This procedure is necessary to contain all the moisture possible for the rooting plant. If you have a terrarium or an unused fishbowl in which you can drill holes, you can save yourself the necessity of having to handle so many separate pots. You can set out quite a few cuttings in one of these larger containers quite efficiently.
Once the slips are in place, put the containers in a shaded spot and keep the soil moist. When they have produced roots which are an inch or two long, it is time to move them to individual pots containing your standard potting soil. As indicated above, this stage should come some three to eight weeks from the time the slips are cut, depending on the plant. Patience is a virtue that pays off with cuttings, don’t dig them up too often to inspect the roots or you will injure them. After they have been set out for a three or four week period, hold the stem at the base of one of them between your thumb and first finger and give it a gentle tug. If it resists, then dig it out and check the roots. The roots of any group of cuttings from one plant should grow at about the same speed, so you can judge the progress of the whole group by inspecting just one plant.
Although you must make sure that your cuttings have sufficient moisture, if they are properly covered they will probably not need to be watered too often. It is a good idea to check them once or twice a week and at the same time give them a short airing. When the time comes for transplanting, remove the covers, transplant the new plants and give them another good soaking. They should then be kept in the shade for another couple of weeks before being moved into a light and sunny location.
There is no set season which is best for making cuttings, any time from late February to August is all right for most plants.
Of the most popular house plants, Impatiens or Patience plant, English Ivy, Coleus, Geranium and most varieties of Philodendron lend themselves best to this method of propagation.