Plant Propagation: Different Methods
PLANT propagation is one of the most fascinating and interesting of the gardening arts, and one from which it is possible to gain much pleasure and a great sense of achievement. Success is often attributed to the possession of ‘green fingers’ — a belief which is not without some foundation. It is true that some people are gifted and have little or no difficulty in propagating young plants, especially by vegetative means such asor ‘slips’. But there is no reason why others should not successfully propagate many different kinds of plants, provided certain essentials are borne in mind and applied.
The methods by which plants may be propagated are many, but generally they may be grouped under five main headings: Seeds, Cuttings, Division, Layering, andand Grafting. The first is known as seminal propagation, and the other four as vegetative propagation. Propagation by seeds, cuttings, division and are the methods that mainly concern the beginner, although, with experience, budding and are not beyond the scope of those whose enthusiasm is not damped by early setbacks and failure.
Only by working with plants and observing their habits and modes of growth can the gardener know instinctively which method of propagation to apply to any given plant. Generally,, and most perennials are grown from seed, but established perennials can usually be divided. Shrubs, soft fruit and trees may be started from cuttings, while such plants as the strawberry, which produces stolons or runners, can have their ‘daughter’ plants severed from them in the summer.
Nature’s method of reproduction is by seed and wherever possible it should be used, for not only is it an easy means of securing a large number of young plants, but plants raised from seeds are usually more healthy and less prone to disease. They are completely ‘new-borns’ that have been derived from the fusion of two cells, one male and one female. Seedlings raised from a plant of mixed parentage (a hybrid), or from one that has been cross-pollinated, will not produce plants that are identical in habit, form and colour of flowers to either parent. The amateur should, therefore, obtain seeds from reliable sources — that is, from seedsmen who are experts and have reliable supplies from certified stocks, or by purchasing seeds in packets which bear a reputable trade name.
Vegetative propagation includes the many and varied methods in which parts of living plants other than seed are used. Plants that are propagated by vegetative means have a separate existence, but they are not completely new plants in the way thatare, because their characteristics are exactly the same as those of the parent plant. For example, if division is used to propagate a given variety of Michaelmas daisy the part divided from the parent will grow in the same way and be identical in habit, form and colour of flowers to the original plant. This is also true of cuttings taken from the varieties of or carnation. The size of the plants may, however, vary because of the season or the richness or poorness of the .
Seed is the best method of raising quantities of plants required for spring and summer bedding displays, such as antirrhinums, lobelias, marigolds, stocks, asters and petunias. Greenhouse plants such as calceolarias, cinerarias, schizanthus, primulas and cyclamen are also raised in quantity from seeds. It is also the only method of propagation for annuals and biennials, which flower, seed and die in either one or two years.
STORAGE OF SEEDS
If seeds purchased from a seedsman or shop are not sown immediately they should be stored correctly, otherwise the percentage of germination will not be as high as it should be. The seed is a resting stage in the life history of the plant and, although dormant, is alive and capable of promoting growth as soon as it is subjected to warmth and moisture. Under natural conditions seeds fall from the parent plant and spend their resting period among fallen leaves and loose soil, often being frozen or in a fairly low temperature; when warmth and moisture arrive with the spring, germination starts. The storing of seeds under dry and warm conditions is, therefore, unsuitable and can result in loss of viability or growing power. Store packets of bought seeds or any that are home-saved in a cool, airy place away from any form of dry heat, and not in an airtight tin. The ideal place is one that is not subject to great changes of temperature, but warm enough to dispel dampness.
TYPES OF SEED
Seeds vary considerably, not only in size and shape, but also in their formation.
SMALL, DUST-LIKE SEEDS
, calceolarias and lobelias are examples of these seeds, which should be sown thinly on the surface of firm and even soil in receptacles. If any covering is given it should be a mere sprinkling of fine sand or sandy soil. To make thin sowing easier, mix a small quantity of fine, dry sand or peat with the seeds in the packet to serve as a carrier and to ensure an even spread as the seeds are scattered. After sowing, cover the receptacles with a pane of glass to conserve moisture and put a sheet of paper on top to exclude the light.
Acorns,, runner beans and chestnuts are a few of the fleshy seeds. Some fleshy seeds become hard externally and have a hard skin or seed coat, especially if they have been stored for any length of time. They should be soaked in water, preferably tepid, for 2-t hours or more before sowing. This will soften the seed coat and help the process of germination to start.
Seeds like those of the sweet pea, the various nuts such as the walnut, hazelnut and almond, and others having a hard outer shell, need pre-sowing treatment to ensure reasonably quick germination. If sown without treatment the seeds may remain dormant for a long time or fail to germinate.
To make sure that the hard seed coats do break down and that moisture enters to start the seeds germinating, chip the outer casing of the seeds with a knife, or file or rub them on a rough surface. The filing or chipping should be done carefully and on the opposite side to the ‘eye’ of each seed, or the embryo or ‘germ’ may be damaged.
On most seeds the eye can be seen fairly easily, because it is the point where the seed was attached in the seed-pod.
There are seeds which have an oily content, and because of it do not retain their viability as long as other seeds. Good examples of oily seeds are carrot, parsnip, celery, castor-oil (ricinus), magnolia and camellia. Do not store these seeds in a warm place and for any longer than is necessary, because once the oily content dries up, the seeds shrivel and will fail to germinate. For this reason it is unwise to retain parsnip and carrot seeds for a second year, because old seeds will either fail completely or there will be very poor germination.
COMPOSITE OR MULTIPLE SEEDS
There are plants which produce several seeds together within a dry or fleshy case. Theis a good example of a dry case which contains several seeds. Thin sowing or station-sowing is essential for these seeds as three or four seedlings usually arise from one station.
The cotoneaster, holly, hawthorn and crab apple are some of the shrubby plants and trees that produce fleshy and often highly coloured fruits with a number of seeds embedded in the pulpy mass.
Before sowing the seeds of fleshy fruits, put the fruits in boxes of sand in a cool, shady place. The fleshy covering will rot away to allow the seeds to be separated. This process is known as stratification.
Its purpose is not only to allow the seeds to be separated from the pulpy matter, but also to soften the hard seed coat or ‘testa’ that surrounds each individual seed and prepare it for germination. The stratifying of seeds will often take several months, so leave the fruits of holly, roses and the firethorn (pyracantha) in the boxes of sand throughout the winter. Place them in an exposed position out-of-doors, where the effects of frost will also help to promote quicker germination when sowing takes place in the spring.