PROPAGATION OF PLANTS

Press, Volume CV, Issue 30982, 11 February 1966, Page 6

PROPAGATION OF PLANTS

Considerable interest is always created in raising one’s own plants, and this can be done in several ways.

By far the most common method is from seed, which can be bought over the counter from various stockists ranging from milkbars to nurseries, or from such establishments as botanic gardens, forestry divisions, or specialists’ clubs.

Most plants are capable of seed production and reproduction but many of these do not come true to form.

Seed sometimes requires special conditions to start it into germination, in spite of completely favourable germinating conditions, such as moisture, warmth, sunlight, ventilation and soil conditions.

The reasons for delayed germination may be due to a seed coat which is impermeable to water, such as are many seeds produced by members of the geraniaceae family; very hard strong seed coats which cannot absorb moisture: or it could be due to the necessity of the effects of a change within the seed itself to take place first. There are various other reasons, too, which can forestall imminent germination. OVERCOMING DORMANCY

Dormancy can be broken by means of stratification (berberis) which may imply exposure to abundant moisture oxygen and cool temperature. It may necessitate the use of acid (cotoneaster) or scarification (peach) whereby the seed coat is scratched with an abrasive, such as passing it between two revolving abrasive wheels. Hot water treatment is used on some seed such as acacia, the seed being immersed in boiling water and then left to cool. Seeds from alpines are sometimes subjected to alternating treatment whereby they are soaked for twentyfour hours, then sown and frozen for another twentyfour hours. In all cases care must be exercised in carrying out treatment and always the final response to germination is dependent on satisfactory conditions being provided both before and after sowing. ANOTHER METHOD Bulbs, corms and tubers are another method of raising plants. The bulbs may be propagated by scooping out the base of the central bud or by cutting it in a certain way so as to promote bulbils or lateral buds. Fleshy-scaled bulbs such as those of the Lilies can be propagated by scale separation, while bulbils formed in the leaf axils provide another means of raising plants. Self-division or the development of offsets from the base, as for example occurs with tulips, affords further means of propagation. Tubers give the opportunity for sectional root stock division while corms may produce, and can be treated, similarly to bulbs. So can rhizomes also. CUTTINGS Cuttings are taken at various stages of maturity in order to perpetuate a particular plant. Soft wood cuttings are taken in spring before there is a trace of lignification of the plant stem tissues. Semi-ripe cuttings are taken in summer (or autumn in the case of some plants) at tlie onset of lignification. Hardwood cuttings are taken in winter when growths are firm and mature. The practice of plant increase by means of root cuttings is practicable as also is the taking of leaf and leaf bud cuttings. These may consist of the leaf with an axillary bud, or no bud included at all. The leaf may be indented on the leaf margins, cut transversely or have the veins severed, each of these methods yielding considerable numbers of new plants. Finally, we come to the methods by which plants are propagated on the roots of

other plants—grafting. This may involve the use of special rootstocks, established trees or potted material using several buds, or a single bud when it becomes a specialised form known as budding. Over the next few weeks : it is intended to give practical details of some of the various aspects outlined in this summary of plant propagation methods. RUNNERS Runners, of which the strawberry plant is most 1 easily associated with, are 1 produced on long or short shoots from the parent crown. Where really good quality plants are desired the runner should be stopped, at most, after it has made two joints. Suckers may be produced from the stem, as in the blackberry, or roots, for example the raspberry. Associated with these natural methods is the forced method of layering whereby root initiation is induced by covering part of the plant with soil. There are numerous modifications of layering such as stooling—cutting the plant back and earthing up the basal shoots then produced; layering down—where the shoots are pegged down, and Serpentine layering—pegging at several nodes; etiolation; aerial; and tip layering.