How to Propagate Roses
The majority of roses grown in the United Kingdom by commercial growers are propagated by the method known as budding, a technique in which a dormant bud of the required variety is inserted under the bark of a rootstock. This system has several advantages; in particular, it makes for rapid and uniform growth of a plant in full possession of vigour from the rootstock. It is particularly valuable in the case of new of scarce varieties, since only one bud is required to produce a plant; in consequence, multiplication can be quite rapid, especially in the hands of an experienced propagator. A good plant can be expected to provide as many as 50 buds in one season, and some of the more robust varieties have been known to produce many more.
I have always been fascinated when visiting rose nurseries in July and August to see the skill and speed with which specialist budders cut out the buds and insert them in the T-shaped cut made in the rootstock. An assistant closes the cut bark around the bud with a plastic or rubber tie stretched over the bud and fixed with a wire staple. These ties eventually disintegrate as the stock swells. Within a few weeks, close examination will ascertain whether or not the bud has ‘taken’. If successful, the stalk ‘handle’ attached to the bud drops off; but if the handle and bud remain brown and shrivelled, it indicates that the union has failed. In this case another bud can be inserted in a new cut made in the opposite side of the rootstock.
Budding is a simple surgical operation which should be performed with reasonable speed, although it takes time to acquire the manipulative skill of the professional. Special budding knives are available in which the handle tapers off so that it can be used to lift the bark of the stock. Remember always to keep the blade of the knife clean (it may carry disease organisms) and very sharp.
In nurseries nowadays dwarf stocks are invariably planted, by machine, about 20 cm (8 in) apart, with 1 m (3 ft) between the rows. These distances allow mechanical cultivation, spraying, and lifting to be carried out, but they are modified by some growers to suit their particular methods or circumstances. Amateurs and small growers who operate on a less ambitious scale generally plant by hand, and rows 100 mm (2 ft) apart will be found quite satisfactory. Plant the stocks so that they lean at a slight angle, which makes budding easier, and place the roots just below ground level. On completion of planting, draw someup by hoe to cover the stem. This helps to prevent the bark becoming hard and difficult to open for bud insertion. Plant in well-prepared soil from December onwards, ending in March in southern England, but extending into April in colder areas.
Stocks are grown mainly by continental specialists, although in recent years interest in stock production has increased in England. Modern stocks, grown from seed, have the great advantage of a good root system, which transplants happily and is less likely to be affected by virus diseases. These stocks are graded after a season’s growth and are generally available in stem thicknesses of from 3 to 5 mm, 4 to 6 mm, 5 to 8 mm, and 8 to 12 mm.
Nurseries generally plant the 5 to 8 mm (3/16 to 5/16 in) size, which grow rapidly in late summer, when rootstocks will reach 12 mm (1/2 in) in diameter. Those who wish to bud early, especially if buds are available from roses grown under glass, will find the larger sizes easier to work with. Northern growers almost invariably use the larger rootstocks. This is because their climate enforces late planting and causes slower growth.
In general, budding is carried out during the months of July and August, when the stock is in active growth and the bark lifts easily. Soil should be drawn away from the rootstock with a hoe or trowel as far down as the roots. Clean the stem with a duster or piece of cloth to prevent soil getting into the T-cut. If the stock has been planted on the slant, push its top growth further over to one side, placing a foot on it to keep it out of the way. Make the cross cut of the T about 25 mm (1 in) above the roots, and deep enough to penetrate the soft bark and free it without method. Pinching back also encourages bushiness.
Budding roses in quantity is quite a strenuous activity and can be taxing for the amateur gardener. If you are interested in this method, you would be well advised to begin with budding half or full standards, which at least is easier on the back muscles. Half-standards are about 750 mm (22 ft) high, standards about 1.1 m (3-1/2 ft), and weeping standards about 1.5 m (5 ft).
The method employed is the same as described for bush plants. The fine old standards sometimes seen in well-established gardens are usually grown on very vigorous stems which were culled from hedges and woodland areas by itinerant workers and supplied to nurseries in the autumn. When planted up in rows they were budded when well rooted and making free growth. This source of supply has virtually disappeared and the workers have found more lucrative methods of making a living. If you are lucky enough to find an available source of Rosa canina (dog rose), they should be budded on side stems which have grown to the correct height. Choose three or four of the best buds, rubbing out or removing any others. Insert the buds on the top side, as near as possible to the parent stem. Such standards are exceedingly hardy and long lived. I have had very good results from R. canina ‘Pfander’, a stock which produces uniform stems rapidly, is fairly easy to bud, and produces few thorns; although it readily produces suckers, these are easily recognized and can be quickly removed. ‘Pfander’ is also reputed to give longer life than standards on R. rugosa.
As standard stems are only one year old when transplanted for budding the following year, the buds can be inserted into the main stem at the required height. Commercial growers usually insert two buds, but amateurs can insert an extra bud to provide an evenly balanced head, staggering them on different sides of the stem.
The most generally used stock for standards is a selected form of R. rugosa which, when pruned back hard the following spring, produces stems 1.5 to 2 m (5 to 6 ft) tall in the second year. Unfortunately some of these stems, which appear quite normal when budded, are infected with strawberry ringspot virus, so that growth from the buds is inhibited and unhealthy. Such stems should be removed and burned as soon as the, disease is apparent, and the supplier informed.
During the past decade much research has been carried out on rose stocks to help commercial growers to select the best for their purpose. Previously, the dog rose, R. canina, was most commonly used. At one time it was grown from cuttings and later from seed known as R. canina ‘Wild’; the seedlings varied widely in quality and vigour and many produced suckers very freely — indeed, far too freely to satisfy the ultimate growers. Some cultivated forms, grown from seed and providing much more uniform growth and less inclination to send up suckers, have resulted in a decline in the use of the ‘Wild’ form; but an ideal replacement has not yet been found.
Most generally grown at the present time, largely because of its low production of suckers, is a variety of R. dumetorum known generally by commercial growers as ‘Laxa’. Many growers raise roses under the protection of glass or polythene, in some cases to produce early blooms, but also to produce early buds. As Taxa’ stock begins growth early, it is very suitable for early budding, producing strong growth which makes a high-quality plant, and it is easy to bud.
R. multiflora and its cultivar ‘Inermis’, which has few thorns, are also popular stocks which make rapid growth and large plants. When grown from seed they produce a good stock for floribundas, but they also suffer from some disadvantages. They do not grow successfully on alkaline soils and produce many surface roots, which are apt to suffer in dry weather and may make budding more difficult. They also break into growth early, so that growers in cold areas have found them unsuitable, and transplanting can be uncertain as the root system is apt to dry out. Some sweet briar, R. eglanteria (R. rubiginosa), is also grown, mainly for late budding, but because it is thorny in the extreme, and therefore unpleasant to handle, it is not a favourite with budders.
Varieties of R. canina, which at the present time are used in smaller numbers, include ‘Brogs’, with few thorns; ‘Heinsohn’s Rekord’, with few thorns and easy to bud; ‘Inermis’, with hardly any thorns and easy to bud; ‘Pfander’ with hardly any thorns and fairly easy to bud; ‘Pollmers’, with few thorns and fairly easy to bud; ‘Schmid’s Ideal’, thorny but fairly easy to bud; and ‘Superbe’, with few thorns and easy to bud. Plants produced on these stocks differ in various ways, including resistance to disease, number ofand suckers produced, and in the size of the mature plant.