Propagation
Plectranthus can be easily propagated using both tip cuttings and stem cuttings.
A. Cuttings can be taken from the tips of non-flowering stems, or from the part of the stem that has not turned woody, known as semi-ripe stems. Although cuttings can be taken at any time of the year, the optimum time is early summer for tip cuttings and late summer for semi-ripe cuttings.
It is easier to take cuttings from a plant that is already growing in a pot. Choose a plant that is vigorous and free from pests and diseases. If you are collecting cutting material from the garden, put the cuttings in a plastic bag straight away to stop them loosing moisture or place them in a container of water.
B. Fill a 10-12cm pot with a proprietary cuttings compost and gently firm it down. To prepare a tip cutting cut the stem, using sharp and clean secateurs or a sharp knife, just below the third set of leaves down from the tip. The point where the leaves attach to the stem is known as the node.
C. Using a pencil, a dibber or a piece of cane make a hole in the compost close to the edge of the pot and insert the cutting so that the first pair of leaves is just above the level of the compost.
D. The leaves of large cuttings can be cut by up to a half to prevent them from touching their neighbours and to reduce transpiration. Semi-ripe cuttings can be taken from further down the stem, cutting just below a node at the bottom of the cutting and just above a node at the top of the cutting.
E. Label the pot, and water the cuttings from above to settle the compost and leave in a shady place. A 12cm pot will generally have room for about five or six cuttings. Pots of tip cuttings taken early in the summer can be placed inside a plastic bag or a propagator but they must be removed for short periods each week to prevent diseases developing in the humid atmosphere. After a couple of weeks give the cuttings a tug to see if roots have formed. Once they have, pot the cuttings into individual containers of potting compost.
NOTE ON NOMENCLATURE All names given are correct at time of going to press but it is expected that some plants will be reclassified as Coleus in 2018.