The propagation of plants is one of the most fascinating areas of the science and art of horticulture, and has increased immeasurably the ability of gardeners throughout the world to maintain, extend and share their collections of plants. In theory there is no part of a plant which cannot be used to propagate a species, for every living cell contains the genetic information of its parents, just as we do ourselves. In practice the ability to successfully propagate plants is not only a matter of technique, but also of available facilities. Nowadays the laboratory has become part of the potting shed.
Generations of gardeners have known that it is possible to get roots on hard wood ‘cuttings’ of trees like poplar and willow which are well over six feet in length. Gardeners the world over utilize the ability of plants to form roots when they insert hard wood cuttings of trees and shrubs far smaller than this – bougainvillea, mussaenda, hibiscus, may all be rooted successfully from hard wood cuttings about 9” to 12” long. They have also discovered that many hard wood cuttings root more readily when they are taken from thick, old wood, as is the case with the bougainvillea and mussaenda.
Coming down from cuttings 10ft long (willow) and 10 inches long (bougainvillea) we are down to selecting cuttings just a few inches long from the semi-hard or soft wood parts of a plant. That is taking them from the youngest parts of the plant, rooting them in sand, and covering them with a glass or plastic cover to prevent or at least reduce the loss of water from the leaves.
For well over thirty years gardeners have benefited from the expertise of laboratory technicians who have been able to extract the tiniest groups of cells from the tip (meristem) of growing plants, place them on a kind of jelly called agar and get them to produce roots.
No hints of potting shed work here. For just as long technicians have been able to extract masses of single cells from plants (usually but not always from the leaf surface), float them in special solutions, and get them to grow exactly like the parent plant.
So from ten foot cuttings, to 10 inch hard wood cuttings, to soft wood cuttings a couple of inches long, to meristem cuttings of a micron or so in size, to single cell propagation.
Gardeners utilize all parts of plants for their purpose. Having just briefly mentioned cuttings from stems I am sure you have all at some time had experience of plants which produce shoots from their root system which can be severed and which will lead an independent life. Think of plants which you have tried to remove from the ground and which keep on sending up shoots from the roots you have failed to get out! The Rangoon creeper is such a plant.
Finally what about leaf propagation? African violets, Kalanchoe, and certain types of begonia, to mention just three plants, may all be propagated from their leaves. With the African violet it is just a matter of severing the leaf with its stalk and putting it into sand or water until roots appear. With Kalanchoe (particularly K. blossfeldiana ) one just has to place the succulent type leaf sideways on into sand and wait patiently. Begonia rex, and several of the other large leafed, thick veined types like Begonia ‘Iron Cross’ can be propagated simply by taking a healthy leaf off the parent, laying it flat on a sandy surface after slitting the veins on the underside every few inches to encourage root formation, and pegging it down with hairclips or something similar, watering thoroughly, and then making sure that it doesn’t dry out by covering the container with a glass jar or clear polythene bag (taking care to remove the moisture from the inside every day).
Until next week may your God go with you wherever you may be.
