Propagation Of Roses
Propagation - the creation of new plants is one of the great pleasures of the horticultural world. Propagation lies at the very base of horticulture. Whether from seed, cuttings, grafting or budding, the result is the same -a new generation of plants. Through centuries of trial and error, propagators have discovered the easiest ways to produce the many plants that gardeners have been interested in growing. Several methods of propagation are used. Each method has its own merits and problems. Some methods work for some roses and not for others.
Starting Roses from Seeds
Growing roses from seeds is the oldest form of propagation. Growing from seeds is not difficult and requires a minimum of equipment. This includes pots, sowing flats, and ideally a green house or fluorescent lights. If you do not own a greenhouse, you can grow seeds on a windowsill, under lights in the basement, or outdoors in containers or the ground.
About one year will have passed from the time a cross is made until the seedling of a new variety first blooms. For most growers the prospect of beholding a new and unusual variety makes the wait worthwhile.
Propagating roses from stem cuttings
One of the simplest techniques of propagating new roses is to cut off pieces of stem and plant them directly into a growing medium, where they will eventually take root. Commercial growers use stem cuttings primarily to multiply miniature and old garden roses, which take root readily by this method. However, some large modern bush roses, especially the larger and more vigorous varieties, can also be rooted from stem cuttings. Like budding, rooting stem cuttings is an asexual method of propagation that produces plants identical to the parent.
To take a stem cutting, use pruning shears to cut a 4- to 6-inch length of stem, making sure that the cutting has at least four five-leaflet leaves. Make the cut at a 45-degree angle, just above the highest leaf that will be left on the plant. It is sometimes possible to cut a longer stem and make two cuttings out of it, but the upper portion will usually root better.
The best time to take the cuttings is right after the flowers have faded, when the wood of the stem is neither too soft nor too hard and will thus take root readily. Remove from the cutting both the two lowest leaves and all its flowers and flower buds, then poke the cutting into a container of soilless medium. Make sure that the medium covers the two nodes from which leaves were removed. Use your fingers to firm the medium around the cutting.
Cuttings will root more quickly if you dust their bases with powdered rooting hormone before placing them in the medium. Rooting hormone is a powder available in packets or jars at garden centers. Cuttings that are started indoors will root faster if heated gently from the bottom. You can supply this warmth with a heating coil, a special electrical device, or by placing the cuttings on top of a warm appliance.
If you are rooting cuttings in the house, place the container in a plastic bag and set it in bright light but not direct sun. Remove the plastic bag for a few minutes each day to circulate the air and prevent disease. After several weeks test the cutting for signs of root growth by tugging lightly at the stem. If it offers resistance, the cutting has rooted. Remove both the plastic bag and the source of heat. If the cutting pulls out freely, replace the bag and wait several weeks before testing the cutting again. If you have access to a greenhouse, so much the better. Its moist environment is exactly what young cuttings need. You do not need to place them in plastic bags, but frequent misting helps them root more quickly.
Rose cuttings can also be rooted outdoors in beds of well-prepared soil, as long as the beds are not in full sun. Prepare the cuttings as you would for rooting in containers, and keep the air around them moist until they take root. You can do this by daily misting or by covering plants with plastic film stretched over a frame or glass jars. The plastic or glass will retain much of the soil moisture, but check for dryness and add water as soon as the ground starts to dry out. Test the cuttings for rooting, and remove the plastic or glass when rooting is complete. Apply extra winter protection to get the plants through the first winter, because young rooted cuttings are more vulnerable to the cold than mature plants. Cuttings can be moved to their permanent positions the following spring.
Reproducing roses by division
Division is the least popular method of reproducing roses because it cannot be accomplished with budded varieties. However, it can be done with any rose that is growing on its own roots. A rose is divided by cutting it in half lengthwise, thus making two plants from one. Division can also be used to thin old, overgrown plants. Roses should be divided in early spring or late fall when the plants are dormant. In warm climates plants should be divided in winter.
To divide a rosebush, dig it from the ground after a thorough watering and examine it closely. The goal is to split the plant lengthwise so that each half will have an equal number of canes and roots. With a sharp knife or a pruning saw, carefully sever the plant in half by cutting through its crown. Then brush on tree wound paint or orange shellac over the exposed areas. Replant the two divisions as soon as the sealant has dried.
Budding is by far the most widely used method of producing roses. Success with budding, even on the smallest scale, gives one a very satisfying feeling of achievement and there is no reason why the amateur should not try to produce a few rose bushes by this means. All that is needed is a budding knife with specially shaped blade and handle, available, in various designs. Budding is an acquired technique, and nurseries employ skilled propagators who are capable of working very rapidly, handling up to 400 bushes an hour. Speed is essential since budding is usually done at the peak growing season with both stock and scion in active growth. Stocks for this purpose are normally planted as one-year seedlings in rows during the preceding winter. By mid-June these are ready for budding and will remain in this state of readiness for about two months. The stocks are planted in such a way as to leave 1-2 inches (2.5 - 5 cm) of root protruding above ground level. The scions or buds are selected by taking a ripe flowering shoot from a ready-made rose bush. The shoot is usually ripe when the flower has started to open. The flower and the top 2 inches (5 cm) of the stem are removed together with the leaves, to facilitate handling. It is a good idea to leave about 1/3 inch (1 cm) of leaf stalk attached to the stem, depending upon the cultivar. Most rose 'sticks' will have between four and eight buds. At no time must the stick be allowed to become dry. It can be kept fresh for several days if necessary by placing it in damp newspaper and polythene.
To perform the budding operation, first make sure that the stock is clean and free of soil at ground level. Open the bark of the stock with the knife to form a T-shaped cut, taking care not to damage or scrape the tissue inside the bark. A vertical cut about 1 inch (2.5 cm) long is enough to tease back the bark at the top of the 'T'. The stock prepared, the scion is then placed in the free hand and held by the index finger and the thumb, palm uppermost, with the thin end or top of the scion pointing towards the wrist. The index finger should be placed directly under the first or top bud on the stick to give support. The first bud is then cut from the stick with one cutting motion of the knife. With the thumb of the knife hand, press the 'sliver' that is being removed firmly on to the knife blade. Having made a clean cut to about 1/3 inch (1 cm) above the bud, the bark can then be torn back to remove it completely from the stick, still holding it between knife blade and thumb. Experts retain the stick in their hand as they complete each budding operation but at this point the novice is best advised to place the stick aside and retain only the bud between finger and thumb. The wood from the bud is then separated from the bark, usually in two stages. Holding the blunt end between thumb and finger, with the thumbnail for support, remove half the wood from the top downwards and the other half from the bottom upwards, exposing a plump little bud on the inside of the bark. If there is a hole instead, throw it away and start again.
The next stage calls for dexterity. Hold the top end of the bud with one hand, and use the other to hold open the bark of the stock with the handle of the budding knife; then carefully slide the bud into position under the bark of the stock, finally cutting off any spare bark from the bud at the top of the 'T'. Lastly, the wound has to be bandaged, both to hold it together and to prevent moisture getting in. Nurserymen use special, inexpensive latex patches for this, but if these cannot be obtained, use some thin raffia, winding it around the cut: beneath the bud three times and above the bud four times, and knotting it carefully at the top. After three or four weeks the 'bandage' can be removed; success or failure will be immediately obvious. If the bud has failed to take and there is still time, another attempt can be made on the other side of the stock. If it has taken it should be left untouched until mid-winter, when the complete top of the stock should be removed at about 1/3 inch (1 cm) above the bud.
Layering is not often practiced with roses but, depending upon the cultivar, it is quite a feasible method of propagation. Although it is not possible with sturdy, upright growers, since they will refuse to bend to the ground, it is, however, a fairly efficient way of propagating the more flexible old-fashioned roses, climbers and ramblers.
Simply arch a one-year shoot to the ground and place the point of contact -about 12' (30 cm) from the tip -into a shallow trench, tethering it with a wire pin or similar aid. A knife wound in that part of the bark which is placed underground will sometimes aid rooting; then cover with soil. This can be done at almost any time of the year but rooting is naturally quicker in spring, just before seasonal growth begins.
Once rooting has occurred, the protruding tip will start to grow and the parent shoot can be cut away. The new rose can then be transplanted into a permanent position at any time during the dormant season.
Micropropagation of plants is a form of vegetative propagation carried out in sterile growing rooms or laboratories. Roses produced in this way are grown on their own roots, like cuttings. Before the technique was discovered, biologists and botanists believed that roots and shoots could be formed only from the actual growing parts of plants. Micropropagation is a type of tissue culture and involves the taking of a small piece of tissue, or even a single cell, from a growth point or axillary bud and stimulating this to produce more growth points which, in turn, produce more and so on. At first the shoots are without roots, so these are induced by adding naturally occurring, root-stimulating hormones to the medium in which they are grown. Once roots have formed, the tiny plants are grown on for a time and then carefully weaned into ordinary compost to take their place in the outside world.
There is still some way to go before this form of propagation becomes common practice in the commercial production of roses. The most difficult stage is the weaning of plants into ordinary soil, but research work is going on all the time and there is no doubt that ways and means will be found to make this easier.
Not all types of roses take readily to micropropagation. Hybrid Teas and Floribundas, by and large, do not grow as well on their own roots as they do when budded, and some shrub roses are even more reluctant. Many of the Miniatures and Procumbents seem to thrive, however, and it is these that are mostly produced by micropropagation at present. This is probably because plants formed in this way sprout many more shoots from the base in the first year than those produced by budding or from cuttings. One significant advantage of micropropagation is the speed of rooting; another is the large number of plants produced from just one small piece of tissue. By harnessing this technique, breeders can build up numbers and launch new cultivars far more quickly than by conventional means, but this practice is by no means widespread.
Grafting and budding accomplish the same task. Only the technique differs. Instead of placing a bud under the bark, a section of stem is placed on top of the rootstock. Grafting is usually done on dormant rootstocks in winter or very early spring. Several different methods are used to join the variety to the rootstock. The most commonly used are the splice graft or, alternatively, the whip-and-tongue graft.
Two things are absolutely necessary to the success of grafting. You must have a razor-sharp, thin-bladed knife and tough fingers. Rose thorns are difficult to deal with at the best of times, but they can be a real nuisance when you're grafting. Grafting requires dexterity, and gloves just get in the way. However, if you have thin leather gloves, you may find them useful. Many rose varieties have thorns that are easily removed by gently pressing them sideways. Your job will be much easier with such roses.
To make a whip-and-tongue graft, cut the rootstock with a sharp blade just above the roots at an angle that leaves the length of the exposed surface about three times the diameter of the stock. Halfway down the cut, and with the blade pointing down the slope, make a second cut. When making this cut raise the blade just slightly from the surface, so that a thin flap is created. This cut should be no longer than one-quarter the length of the exposed surface of the initial cut. Using a section of stem containing one to five buds, make the same sequence of cuts on the bottom of the piece from the desired variety. This piece is referred to as the scion. Slide the scion down onto the rootstock. The thin flaps at the center of each cut should lock the two pieces. Fit them gently and snugly together. If the cuts are flat and the flaps are thin, there should be good surface-to-surface contact. When you fit the graft, it is essential that at least one side of the union have the cambiums aligned. (The cambium is the thin green layer just under the bark.) This is where cell division occurs and therefore where the two sections will knit together. Without proper alignment, the cells will not be able to connect, and the graft will fail. If the scion and rootstock are different sizes, make certain at least one side is aligned.
Once you have locked the two pieces together, bind them tightly with a budding rubber, masking tape or even string. When tying, be careful not to shift the alignment. Once tied, brush on a grafting wax to seal the graft. This will prevent the graft from drying out before healing takes place. Several grafting waxes are available on the market. If you are unable to find a commercial preparation, melted paraffin wax will work.
There is a variation of the grafting process. This technique is used in the greenhouse, but could be adapted to a cold frame or humidity tent. Collect sticks of both the desired rootstock and the variety in late spring and summer. Only slightly hardened, new wood is used, and this should be vigorous and reasonably thick. First remove the leaves from the rootstock sticks. Cut these sticks into sections 3-4 in (8-10 cm) long, being sure to keep track of which ends are top and which bottom. Using a sharp knife, make a vertical cut down into the center of the top of a rootstock section. This cut should only be 1/2 in (1.3 cm) deep. Next cut a section of the variety stick, leaving 2 or 3 leaves on each section. Slice the base of the variety section into a 3/4 in (2 cm) long wedge. Using the tip of the knife to open the top of the rootstock section slightly; insert the wedged end of the variety into the cut, aligning the cambium layers as you do so. Push the wedge far enough so that it is snug, but not so far that it will split the rootstock section. If properly made, the graft will be snug enough without needing to be tied.
Dip the base of the completed graft into a rooting hormone. Gently stick the cutting into a rooting medium, which should be clean and perfectly drained. A mixture of 4 parts perlite to 1 part peat works well. Clean sharp sand will work as well. If kept sufficiently moist and warm, this grafted cutting will root within two or three weeks. Once rooted it can be potted up until it is sufficiently acclimatized to be planted outdoors.
Grafting is a reasonably simple and rewarding technique for producing roses. Like budding, it creates plants that are the union of two different varieties, and the problems of suckering and rootstock hardiness are the same. On the whole, grafting is somewhat more reliable than budding when done on rootstocks growing in the field. Newly budded roses can suffer winterkill in areas with very low winter temperatures, especially when there is no snow cover. Grafting is one of the oldest propagating methods for roses, and it is still one of the most dependable.
Hybridizing is the inducement of hybrids or crossbreeds by the deliberate crossing of two species or cultivars. Hybrids can also arise from the natural cross-pollination of two plants by insect activity. In days gone by, rose growers would collect the hips of roses grown in close proximity to others in the hope that nature had taken its course and produced hybrids. Nowadays hybridizing is more sophisticated and breeders create their hybrids by the deliberate cross-pollination of two pre-selected varieties. To be sure of success, cross-pollination is best carried out under glass. In a greenhouse regime, roses are induced to flower earlier and this enables seeds to ripen fully, even in the most inclement summer.
In botanical terms, the flower of a rose is perfect Both male and female organs are present in the same structure. To avoid self-fertilization, the male parts of the flower, the anthers, are removed before pollen is applied from another flower. This is termed 'emasculation'. During this operation care is required to avoid any damage to other parts of the seed pod or 'receptacle'. In order to remove the anthers, the petals must also be removed. The timing is fairly critical in that the flower should be fully developed and ready for fertilization and yet in a state when no self-pollination or chance cross-pollination could have occurred. This, in the case of a rose, is at a time when the petals are still furled around the reproductive organs, and just before the pollen is ripe.
Knowing full well that nothing is predictable when crossing two hybrids, hybridizers usually give careful consideration to the merits of possible offspring by looking at the pedigree of the roses they wish to cross. In this way they hope either to perpetuate a particular attribute or to avoid a serious fault. All possibilities are considered, such as color, fragrance, habit of growth, foliage, hardiness and, above all else these days, resistance to diseases.
Having prepared the seed pod by emasculation, pollen from a selected pollen parent is applied to the stigma a day or so later when it has become receptive and slightly sticky. This stickiness normally manifests itself as a change of color from creamy-yellow to orange or gold. Pollen is applied with a camelhair brush or direct from a fully open flower removed from the parent plant. Depending on the variety, pollen grains can be large, plentiful and very visible, or small, scarce and difficult to see with the naked eye. Most modern roses are fairly free with their pollen so that, depending on the method used to apply it, pollen from one male can fertilize several seed parents. After the pollen is applied, the cross is recorded on a label which is attached to the stalk below the pod. The standard method of recording crosses is with the seed parent's name written first. If crosspollination is successful, the seed pod starts to swell and ripen and after about six to eight weeks turns orange or red. At the end of the summer the hips are collected and the seeds removed. Each separate lot of seeds is best placed in a small polythene bag with their label, so that they can be handled easily.
It is important that rose seeds are exposed to fluctuating temperatures while dormant in the winter. In days not too long gone, they would be mixed with sand and placed outside to take all weathers, a process known as 'stratification'. To achieve the same effect these days, some breeders leave them in a freezer for a few weeks prior to sowing. Before sowing, germination can be improved if they are soaked for a time in a mild solution of gibberellic acid. Seeds are sown about half-an-inch (1.25 cm) deep into good compost on a bench in a preheated greenhouse in February. Germination is erratic and usually starts in April when the soil temperature is at about 7-10°C (45 - 50° F). After germinating, the seedlings grow quite rapidly and some can be in flower as little as six weeks later. At this stage only the best and most promising are kept. These are potted on or budded outside in the nursery for further observation. At the seedling stage as few as 10 per cent are sufficiently different or promising enough to warrant further testing. After the first year of trial out of doors, less than 1 per cent of those originally selected will be considered good enough for further or prolonged trials.
Planting bare-root roses
Bare-root roses can be planted at any time during the dormant season, which in the northern hemisphere usually means between the last week in October and the end of March. They should not, however, be planted during heavy frost.
Roses prefer good, deep, heavy loam, but with a little help they will grow in most soils. Do not despair if your soil is light and sandy or even chalky, for a careful choice of type and variety should still produce fine blooms. A good rule of thumb is to choose vigorous roses for light soils. Providing your soil has a pH of between 6.5 and 7.5, is of reasonable depth and your roses are given some love and attention, they should succeed in almost any conditions.
When planting a new rose, it is important to incorporate as much organic material as possible in the soil that will be packed around its roots. Well-rotted farmyard manure is best, but if this is not readily available then a mixture of peat and bonemeal -one handful of bonemeal to a bucketful of peat -makes an adequate substitute. Whatever is used must, however, be well mixed with the soil before planting. The hole should be large enough to accommodate the rose without cramping its roots and should be deep enough to enable the union -the point where the roots and shoots join -to be placed about 1 in (2.5 cm) below ground level. When the soil is replaced around the root it should be trodden firmly enough to eliminate any air pockets, with the last spadeful being used to cover footprints and to provide a good tilth around the plant. A top dressing of bonemeal or proprietary rose fertilizer will help the rose get off to a good start.
Planting distances vary according to the type of rose, but most modern Hybrid Teas and Floribundas are best placed about 24 in (60 cm) apart. Shorter varieties will tolerate 18 in (45 cm), and some Compact Floribundas and Miniatures can be planted even closer than this.