PROPAGATION OF PLANTS.

New Zealand Journal of Agriculture, Volume XVIII, Issue 2, 20 February 1919, Page 93

PROPAGATION OF PLANTS.

METHODS IN REGARD TO CUTTINGS.

By

W. H. TAYLOR,

Horticulturist.

There is no plant that is not amenable to propagation in some way ; it is a provision of nature that every living thing shall be capable of increase. In most cases plants increase with the greatest freedom,' though that may occur only in their native habitat. It 'is said that every portion of a tree or plant contains all the necessities for' the making of a counterpart of itself, but in very many instances the nature of the wood of the plant renders it impossible to cause such development.

In nature plants are mostly propagated by seed. Under artificial conditions resort must in many cases be had to other means. ’ In 'some instances propagation can be carried out almost without limit in numbers by means of cuttings, which, after seed, is the most prolific mode of propagation. Other methods of propagation are by layering the branches ; by division of the rootstock, ' as in the case of fibrous-rooted iris, perennial phlox, and many other herbaceous plants; by division of the tubers, as with dahlias, tuberous-rooted iris, alstromeria, and plants with like roots ; by dividing the rhizomes, as with Solomon's seal; by increase of the bulbs, as with lilies, narcissi, and other bulbous-rooted subjects ; by using leaves as cuttings, as is done with foliage begonias, sometimes' tuberous varieties of begonias, and gloxinias ; by budding and graftingthough these two operations are rather to preserve and increase varieties than to make a plant, for the plant must exist before either operation can be performed, and therefore neither budding , nor grafting really effects an increase, though possibly this may be a new point of view. Lastly there is propagation by cuttings of rootsthe best means in some few cases. There may be mentioned apple-tree roots to make stocks, some tecomas, Ailanthus glandulosus, many herbaceous plants, amongst them Anchusa italica and Verbena venosa, which are most easily increased in this way. Those lovely flowering-plants, bouvardias, are easily progagated by root-cuttings, and the greatest increase as well as the strongest plants are secured in this way. ' . . - -

PROPAGATION BY CUTTINGS.

To be successful in the general propagation of plants by cuttings some knowledge of the nature of the plant dealt with is necessary, also the theory of plant-growth must be understood. It must be recognized that top growth makes roots, not roots make top. The growth of a cutting proceeds in the same sequence as the growth of a seed. The seed-leaves appear before roots are made, and so it is with a cutting —- roots do not begin to form until some top growth has been made. There may be some cases where this statement may appear to be open

to question, but investigation will show it to be right, and the statement stands.

Success in getting cuttings to root depends very much on the recognition of the truth just stated, for it is only by keeping life in the cutting until roots are formed that success can be attained. Cuttings that are struck in the open ground or in boxes without protection are mostly put in at a time when sun-power is low. Cuttings that take a long time to root cannot possibly succeed at any other time, because they perish for want of roots to supply them with moisture. Pelargoniums, which have fairly solid yet succulent' wood which stores up a lot of moisture’ are successfully struck early in . the —February—while the sun is hot, but besides their structure fitting them to bear heat without perishing they root quickly. But pentstenions would fail at that time, April being a better period for them. Cuttings of shrubby calceolarias should not be put out till May, when every cutting will root. And here an apparently curious thing may be mentioned. Delay putting in the cuttings till . mid-June and the chances are they will fail; but if at that time they are planted in boxes and placed in a cold frame all will root. One need not look far for the reason. The plant loves cool conditions, and during hot weather it is only surviving ; therefore cuttings separated from ■ the plant while the weather is hot wither away at once. Take the cuttings* in May and the cool conditions enable them to keep alive for some time" without roots, which are not made until the days begin to lengthen and the weather becomes warmer. In the meantime the callus has formed ; this prevents loss of sap, and roots soon come when the days lengthen. But put the cuttings in much later and the callus will not have formed in time to make roots before the weather becomes too warm for them to survive without roots. In a cold frame, however, the cuttings are protected from the weather and in a moist atmosphere which feeds the leaves, consequently they succeed.' This is the general principle which guides the propagator of plants by cuttings. Most trees and shrubs that are quite hardy have qualities that are strongly resistant to. decay, and can survive without roots for a considerable period, provided the soil and atmosphere are both moist. Cuttings of these will root in the open air during the period of short days. The kind of cuttings, and the time of taking it is a matter of varying importance. In the case of the more difficult plants, such as heaths, success is impossible of attainment unless there is a full understanding on these points. .. Many plants, such as the common fuchsia, can be propagated at any time when young growths are obtainable, though the means required vary according to the time of year. A little bottom heat is -required in winter or spring, while a sheet of glass over the pot is sufficient during the summer months. These plants can also be increased by cuttings of older wood put out in the open ground, but the resultant plants are less vigorous than those from young shoots, which alone provide plants suitable for pot culture. Most hardy shrubs can be propagated by cuttings of fairly young compound tops made 8 in. to io in. long, the base cut square across just below a joint. Others will root only if smaller shoots are taken, and with a heel, of the old wood. This is the case with’ conifers, most of which, other than the pines, root quite freely. In other cases it is necessary

to take .the same kind of cuttingthat is, with a heel, but before the growth is quite matured“ half-ripe ” is the term used. Clethra arbor ea and Choisya ternata are instances of this. There are also other methods, chiefly economical, which need not be mentioned, as they are not conformable to conditions in this country.

SOIL FOR CUTTINGS.

Soil that will not set hard during dry weather nor run together in wet weather, and that will hold a fair amount of moisture in summertime, is suitable for open-ground work. Light manuring is advisable if. the soil is poor ; most of the plants raised from' cuttings in the open ground have to pass a year in the cutting-beds, and little growth would be made in poor ground. Cuttings of soft-wood plants that are struck in pots or boxes usually remain in them but a short time, - and in this case the quality of the soil, apart from being mechanically right, is of very little consequence. When,, however, the cuttings are a long time rooting it is almost , a necessity to employ poor soil. The term poor ” here implies absence of manure or fertilizers rather than natural soil of the poorest description, though that description of soil would answer better than naturally rich soil. For cuttings struck in artificial heat soil ordinarily used for potting does very well, with the usual surfacing of sand, of course. For boxes intended for conifercuttings which will not be disturbed for a year anything of a perishable nature, such as leaf-mould, should be avoided. Fairly good and clean garden soil will answer, its quality not being of much consequence, as it will have a covering a good inch deep of sharp sand. For pot-work for shrub-cuttings which will occupy the pots for about a year the quality of the soil is of more importance ; either good fibry loam or a mixture of loam and peat (when it can be got) will answer well. What is required is soil that will keep sweet as long as the cuttings remain in it. Very little top growth will be made in the boxes or pots, for the young plants are to be taken out when rooted and placed where .they will make growth. As top growth will not be made to any extent richness of soil would be wasted. Moreover, the constituents which would make it rich would tend to make it sour. And equally important is the fact. that plants make more roots in poor than in rich soil. • .

STRIKING CUTTINGS IN THE OPEN GROUND.

, For the striking of cuttings in the open ground it is absolutely necessary to make the base of the cutting firm ; soil must come in close contact with it and be trodden firm. The plan is to first dig a narrow strip, keeping a good trench open in front of-the spade. When a sufficient width is dug to accommodate a row of cuttings draw a line along the strip clear of the trench. Then, holding the spade perpendicular, strike a straight wall along the line,- the displaced soil falling into the trench. The depth to strike the wall.depends on the length of the cuttings, which should be uniform. The cuttings are then placed along the line, their bases entering the soil deep enough to keep them in position. When a row is filled with cuttings a light spit of soil is dug against- them and trodden firmly down. Then proceed to dig another strip, filling the soil up to the proper level as regards the tops of the row of cuttings, breaking all. lumps and leaving

the soil in good tilth. Digging proceeds till there is room for another row. The line is then lifted and brought forward, and work proceeds as before.

Gooseberry and currant cuttings are put out in this way, as well as a great number of evergreen shrubs, such as euonymus, escallonia, eleagnus, and olearias. Speaking of escallonias, I am reminded of that fine autumn-flowering species Escallonia montevidensis. So far as I know, this species does not propagate at all freely from cuttings of the kind taken for the others, but small heel-cuttings' inserted in pots and kept in a cold frame root freely. In practice hardy shrubcuttings are set out at any convenient time from the middle of April till the end of August, and it appears to make little difference. The popular shrub known as “musk-tree” is an exception. I find that in the conditions of my own place it does not like to be long in the soil without roots, and dies ; but rather long heel-cuttings put out in September root like pieces of willow. •

METHODS WITH SOME WELL-KNOWN PLANTS.

Some brief details of methods of rooting cuttings of a few wellknown plants will now be given. ’ ■ ■ Among the roses, hybrid perpetuals and most hybrid teas root freely if firm wood without branches is cut to lengths of about 8 in. and twothirds of the length buried in the soil. The last week in April to the middle of May is 'the best time. . Tea roses root ..with equal freedom, but with them - compound sprays must be taken. Tear these off with a heel of old wood, lightly trim the. tops, bury them rather deeply, and nearly all.will root.

Many shrubs, of which Clethra arborea and Choisya ternata are types, can be freely propagated by taking heel-cuttings early in April.' Insert them in pots surfaced with sand, water well, and,place them in a cold frame. ,

With daphne, take heel-cuttings about 3 in. long about Christmas, bed them fairly close together in boxes in free sandy soil, water well, allow the surplus water to drain off, place the boxes in a close frame in a greenhouse, and ventilate + or a few minutes daily. Be careful not to give water except .it be actually needed. Regarding erythrina (coral-tree), my experience is that the old wood will not make roots. Cut pieces of firm shoots of last year into lengths of 12 in. or so, lay them flat on a box of soil in a hotbed, doing This at any convenient time early in spring. Side shoots soon spring from them, and these can be cut off with a little bit of the old bark and used as cuttings ; they soon root in the hotbed, from which they must be gradually hardened off. . Clematis of the garden species will root from cuttings of the young shoots when ripe, but a departure from ordinary methods of cuttingmaking is necessary. The usual plan is to cut just below a joint. If a clematis-cutting is so made it makes such a large callus that roots cannot get through. Leave from | in. to in. of internode and no callus will be formed ; roots will come from the joint. I know these plants are usually raised by grafting, but there is a very strong crusade now being carried on in England against that method, great numbers dying, it is claimed, through being grafted. < They are also' raised by layers.

Passion-flowers of the flowering species are readily rooted in a close frame in a greenhouse. The long' vines may be cut into' lengths of two joints, the lower to be trimmed to form the base, the other forming the top. Place the cuttings as close as they will go in 5 in. pots. Any time of the year is suitable. For diosma the style of cutting usually employed is young tips during summer. A better way is to wait till April, then take small sprays about 3 in. long, each with several branches, tearing them off with a heel of the older wood. Insert these close together in boxes surfaced with sand, water well, and place in a cold frame, or in a sheltered position outside where they will not get too much rain. Remove them to a greenhouse or frame when winter sets in. Smaller cuttings, just single shoots, also with a heel, will root, but they must be kept under shelter, and require a little more skill.

Cuttings of heaths are made about 1 in. long of the last growths. Use 7 in. or 8 in. pots with a good amount of drainage —crocks in the bottom, coarser in the ■ next layer, finishing with finely broken brick or potsherds ; blind with old sphagnum, coconut-fibre, or fibre from loam. Fill the pots half-way with drainage material, and .fill up to within an inch of the top with clean sandy peat or loam, surfaced with clean silver-sand. The cuttings are usually made with a small pair of scissors, cutting just under a joint, and carefully removing a few of the lower leaves. The cuttings may be placed as close together as they will go without actually touching each other. After the pot is filled with cuttings water through a fine rose. Let the water drain off and the cuttings dry, then cover with a sheet of glass. It was formerly the custom to use bell glasses, but propagators now prefer a sheet of glass. When bell glasses were used they had to be wiped out every day to dry them. The sheet of glass has merely to be turned over — a great saving of time. The cuttings are inserted so that their tops are just clear of the glass. The cutting-pots are stood on a bench in the greenhouse, not in a propagating-frame. The time for taking cuttings necessarily varies ; growth must be in a certain condition or they will not succeed.. The months of September and March are periods when most cuttings are taken. Cuttings must be well ripened ; , soft fleshy growths will not root. The thing of most importance is that the growth of the shoots taken must be finished. If the leaves at the top look soft and are bunched together they are not ready. When ready the leaves on the point of a shoot are distinctly separate and fully formed, and their colour is uniform with that of the rest of the leaves.

The time for boronias is the month of March. Cuttings about 1 in. long are prepared as with heath-cuttings, but with the extreme tip nipped off. Strike in a frame in a greenhouse. Every day just raise the light and close it; this will effect a change of air and is all that is wanted in that way. Cuttings of young bouvardia-shoots root readily in a little artificial heat. A more prolific source of increase, and one that requires less skill, is by cuttings of the roots. In early spring lift a plant from the ground or knock it out of a pot, as the case may require. Remove all the soil from the roots and cut off as many as may be required ; those that are as thick as a lady’s hairpin will do, but a little thicker will answer as well. Cut the roots into | in. lengths. Seed-pans are handiest to put them in, but shallow boxes will answer. Fill the pan

with' light sandy soil and lay the pieces of root flat upon the surface, keeping the pieces just clear of each other. Just cover the pieces of root with fine compost and place in mild bottom heat — a hotbed answers well. The young plants will break through in about a fortnight, the time they take depending on the amount of heat. When they are strong enough, which will be before many days have passed, prick them off into boxes and return to heat. The plants so raised usually have several stems, and soon make fine plants, the aftertreatment being to pot them up and gradually harden them off.

Carnation-cuttings —“ pipings ” they are termedcan be rooted at any time of the year provided the means are adapted to the'weather. In spring-time they can be rooted on a hotbed or in a propagating-case in a heated house. During summer the process is carried out under hand-lights or bell glasses in the open ground, selecting a -spot sheltered from the midday sun ; the soil should have a covering of sand.. In autumn, when sun-heat is not strong and the soil is moist, they will root anywhere in the garden (or better in boxes) in a semi-shaded position, but plants so raised are slow in growth and do very little the first year. Pipings are made from flowerless shoots taken off where the substance is firm. Remove a few of the lower leaves and cut square across just below a joint; cut off the tops of the grass, but be careful not to injure the young grass breaking up in the centre. Layering is the best way to propagate carnations, layers providing strong plants straightaway. For layering clear away a few leaves from the base of a shoot, then with a sharp knife make an incision on the under-side, starting just below a joint. Taper the knife in till it reaches near the centre of the shoot, carrying it upward for a little more than | in. Peg the layer firmly into the soil, making the grass stand nearly perpendicular, which will keep the cut open. Pegs may be made of wire in the form of a lady's hairpin, but thicker, or, which is much better, from the ripe fronds of bracken-fern. Layers root in four or five weeks. They should be then lifted and planted in nurse-beds where the soil is of a free nature. When speaking of pipings it was said that the tops of the grass must be cut off. This is done to stop their demand for sap, which there are no roots to supply ; the young leaves in the centre are sufficient to promote the formation of roots. But on no account cut the grass on layers ; the half-divided stem is able to support it, and it effects a rapid formation of abundance of roots. If the grass were cut, nearly all the advantage of layering would be lost.

Pinks —near relatives of the carnation —are easily propagated in autumn by tearing off the shoots with a heel of old wood, bedding them closely in boxes of garden soil with a good surfacing of' sand, well watering, and standing in a semi-shaded position sheltered from strong wind. Practically every piece will root.

Milk-products Investigation. — The officer of the Dairy Division selected to visit the United States and Canada for the purpose of acquiring first-hand information regarding the preparation of milkproducts, such as milk-powder and sugar of milk, is Mr. W. Dempster, Dairy Instructor, Hamilton. Arrangements have been made for Mr. Dempster to leave for America in April.