The Rose Annual (1910) pp. 46-56
Hybridisation of Roses
WALTER EASLEA

The remarkable strides made during the last twenty years in the cross fertilisation of the Rose cannot be ignored, although some grand seedlings were obtained prior to that time, many presumably from promiscuous seed sowing.

Naturally a desire has arisen among the more ardent amateurs to try their hand at this very interesting and fascinating work, and the achievements of such noted amateurs as the late Lord Penzance, Dr. J. Campbell Hall, M. Jules Gravereaux, Dr. Müller, and others, have given quite an impetus to cross fertilisation, which must ultimately result in some grand successes,

That Rose-raising is really a work for the amateur the trade growers would be the first to admit, although one readily acknowledges the indebtedness of the Rose world to the great trade firms at home and abroad who have already produced such a glorious wealth of novelties.

But the close attention demanded in the crossing and raising of seedlings makes a serious tax upon the time of a business man, which he can ill-afford to spare at that season of the year when the work requires to be done. Whereas a number of amateurs working on different lines would most certainly achieve some valuable results.

The untimely death of the late Mr. Girdlestone deprived the Rose world of one who would have been a most successfui raiser, for he was a man with a keen insight and an originality of thought that few have since equalled.

If the amateur hybridiser only succeeds in obtaining some beautiful and original forms for his own garden the effort even then would be well worth making. Who can tell what is in store for us when we hear of a cross between that erratic Rose, Rosa Gigantea and Reine Marie Henriette, named Etoile du Portugal, which may even rival R. sinica Anemone, another of those splendid achievements we owe to the hybridist's art?

As this paper is intended for the novice in Rose-raising I must ask forgiveness if it may appear to other rosarians somewhat elementary. Should the reader desire to study the subject from a more advanced and scientific standpoint I must refer him to the journals of the Royal Horticultural Society, wherein he will find ample material to work upon, and I have given at the end a list of the volumes that contain special articles on Hybridisation and Genetics.

In the first place one must possess a greenhouse, for it is practically useless attempting the work outdoors in our variable climate, although I know some who have been successful in crossing the rambler Roses in the open garden.

But the majority of beginners will aspire to raise novelties of the type of Mme. Mélanie Soupert, Betty, Dean Hole, &c., and this can only be done under glass.

A Lean-to Greenhouse is the best form of structure, having a south aspect. As it is essential to commence early in the spring so that the seed-pods may have a long season for ripening, the greenhouse must be constructed to obtain all the sunshine possible. I do not say a lean-to house is absolutely necessary. A span-roofed one would do if not overshadowed by trees or buildings. Supposing one possesses already a greenhouse, the warmest end could be partitioned off for the actual work of crossing, providing it be supplied with two rows of 4-in. hot water-pipes with controlling valves.

A structure about 24-ft. long and 8-ft. wide could, by means of a tiered staging, be made to hold 100 plants in 8-in, pots. Whatever structure be used, it must be so arranged that a strong heat can be obtained when the Roses are in bloom. Needless, perhaps to say, the greenhouse, whether partitioned off or not, must be devoted solely to Roses, as will be seen later on.

Having provided the greenhouse, the next thing to consider is the Plants for supplying blossoms for their pollen, and others to be utilised as seed-bearers. Before stating in detail the varieties to use, the question arises what kind of plant to secure.

It is well known that highly-nourished plants are the very worst seed-producers, so that it is best to secure plants that are of moderate vigour, such as gardeners sometimes discard. They must, of course, be healthy at the root, but the wood may be weak, rather than over luxuriant.

The plants, too, should be well established. Growers of pot-Roses for sale often have a number of what they would term second quality plants, or perhaps some that have not been re-potted for a year or two. Such plants are the very best to operate upon.

It may be best in the first instance to briefly describe the details of growing the plants, of cross fertilising, and of the care of the plants afterwards, as well as of sowing the seed and developing the seedlings.

Supposing the plants are all in readiness, they should be brought under cover in November. Plenty of air should be given for two or three weeks when the plants may be pruned. Do not cut back severely, as the well ripened but thin laterals are often most suitable or our purpose. The plants should receive the same care that is given to ordinary pot Roses, watering them when needed and syringing them on fine mornings. No liquid manure should be given, but ample water is necessary when the growth is active. A temperature of about 45° by night and 50° by day should be the maximum at the commencement, increasing this week by week until 55° by night and 60° by day is reached. When the sun shines, the thermometer will often go up to 75° and even 80°, but this will do no harm providing a nice growing, humid atmosphere is maintained. The plants should be in bloom early in March. Some varieties come on much slower than others, so the thin Teas should be kept in another house or cold pit until the H.P.'s and H.T.'s are advanced in growth a little, otherwise we shall have the Tea Roses out of bloom before the others come on.

If a trial is to be made with Rambler Roses, these being rather slow in growth should be brought in earlier. There is an idea abroad that the plants must be subjected to a sort of roasting right from the start. This should not be, simply grow them rationally until such time as they commence to bloom.

Insect and fungus pests will be a source of trouble, but green fly can be effectually kept in check by means of McDougall's tobacco sheets, and mildew is best combated in a small structure by syringing the plants with carbolic soap solution, Mo-Effic, or Cyllin soft soap. Red spider will be our worst enemy, especially later on, therefore before the plants blossom keep it down as much as possible by well syringing the under side of the foliage. When the blooms are being cross fertilised is the time this pest gains the ascendency, as, of course, no syringing must be done, and the floor and all parts of the house should be kept as dry as possible. I have known some plants to lose all their foliage even before the seed pods were ripe, but this did not seem to materially affect them as regards bringing their seed to maturity. During March and early April the plants will be in full bloom. The ingenuity of the hybridist will now be taxed to the utmost for it requires some skill to obtain the various varieties in blossom at the time they are required, either for their pollen or for using as seed bearers. When any variety blossoms and its pollen is not immediately wanted the pollen may be preserved in small glass vessels, well corked, without losing, its power. I have preserved it by dusting the pollen grains on to small pieces of clean glass, laying another piece of the same size upon it and labelling with stamp paper. Lord Penzance believed pollen improved with age, but most hybridists prefer to use it within a few days of its maturity.

The operation of crossing the flowers is very simple. In order to prevent the bloom fertilising itself we must remove the stamens before their pollen is developed. To do this one must operate upon the flower in the early bud stage. Cut right round the bud towards its base with a sharp knife without cutting the calyx if possible, and gradually pull off the petals until the stamens and pistils are seen. Some varieties of the thin petaled Roses may be readily pulled to pieces without cutting, even when the buds begin to show colour. Having reached the stamens, these are removed with a pointed quill, small scissors, or something that will do the work without bruising the delicate parts that surround them. Frequently the stamens are found quite hidden at the base of the pistils. It is only necessary to remove the anthers or pollen bearing heads of the stamens, but every one of these must be removed. In order to see that they are all emasculated a powerful magnifying glass is useful. I use a glass such as linen merchants employ to examine the texture of the various fabrics, and I have been amazed at the wonderful beauty and individuality revealed in the fructifying organs of the various kinds. Having prepared the blossom ready for crossing, it should be enveloped in a small paper cone, screwed tightly at the top, and tied tightly beneath to the stalk. This answers the purpose of excluding insects which might pollinate the bloom, and also to raise the temperature which is favourable to impregnation when the pollen is applied. This should be done about three days after the bloom has been prepared.

A paper label tied on to the stalk answers the double purpose of securing the paper cone and providing a place on which to enter the date when the bloom was emasculated and the details of the cross.

I have found the best method of applying the pollen is by means of the finger. This is better than a camel hair brush, as one can rub off any pollen grains when the crossing of one flower is completed before attempting another. Just place the tip of the finger upon the anthers of the variety it is proposed to use as the pollen parent and then dust on the pollen grains to the pistil of the seed bearing variety. Having done this put on the paper cone again and retain it there for a week or two. The bloom may be pollinated again the next day to make certain it has been crossed; but be sure and use the pollen from the same flower.

A careful observation of the pistil when the flower is first emasculated and when pollinated will usually show that a sticky substance has appeared since first examined. The pistil is then in the best state for pollination.

I need not say that no moisture must be allowed to fall upon the reproductive organs; the paper cones will, however, prevent this occurring. I owe the hint as to the paper cones to M. Claude Pernet-Ducher, whose talented father has enriched our gardens with some of their choicest Roses.

If a number of plants for crossing have been grown the amateur hybridist will be kept busy for a week or two. It is best to carry out the pollination about 10 a.m. on a sunny day when possible, but of course one cannot always do this. The crossing of such flowers as those of Dorothy Perkins is very tedious, and in their case the magnifying glass will be most useful.

It must not be forgotten that a hot dry atmosphere is necessary during the time of pollination and for a week or two afterwards. Everything, even the soil in which the plants are growing must be kept on the dry side. Let no water be sprinkled on the floor. The plants will need a little water at the root to just keep them alive, that is all. A temperature of 90° by day should be maintained if possible, certainly not less than 80°. After two or three weeks the pods will be seen increasing in size if the pollination has been successful. The paper cones may now be removed. Keep the pods from drip and on no account syringe the plants. Just give enough water to keep them from becoming exhausted. Too much water at the root will often spoil the pods, and they will develop black blotches, even when they begin to show the colour of ripening. When about as large as gooseberries the temperature may be reduced somewhat, and by this time air may be given, increasing this as the summer advances, but always keep the house on the dry side. By June and July air may be left on night and day, and by August the pods will be colouring, some a beautiful soft apricot, others a lovely ruby red, some shaped like miniature Jargonelle pears, others like flat tomatoes. The variation in the shape and size of the pods is almost as remarkable as that of the pear family. I think Mme. Abel Chatenay and Joseph Hill would take the prize for size of fruit, often measuring as much as two inches in depth.

The pods are allowed to remain on the plants as long as possible, then when they are about to drop, gather and duly label them and stick their stalks into pots of sand, that must be kept damp, where they remain until sowing time—November or December.

Sowing the seed is a very important work. I will explain it as briefly as I can. Do not on any account sow it in the open ground or in cold pits. It is far too valuable to risk losing by the depredations of birds, mice and slugs. The same greenhouse that was used for the crossing would do well for the seed raising, giving a temperature of about 50° by night. It is very essential that when once sown the soil should never get dry. To prevent this the best plan is to place a small 60 pot inside a 48 pot. Bring the two rims level by means of crocks beneath the smaller pot and fill up the intervening space with old peat, broken up into small particles. Leave an indention of about half-an-inch so that water can be poured on to the peat without wetting the soil. The small 60 pot is now furnished with one-fourth its depth of small clean crocks, and then filled with a compost consisting of loam, one year old leaf soil, and silver sand, the two first one part each, and the sand half a part. All should be passed through a very fine sieve. Having placed the soil on the bench of the house to air a little, the pots are then filled and the soil pressed fairly firm with the fingers. As only three seeds are sown in one pot, and as one pod will often contain as many as thirty seeds it will be seen that quite a number of these pots are required.

Now proceed to take the seeds from the pods. The pods are broken with a hammer and the seeds picked out. They are usually quite moist with a peculiar acid-like substance supplied by Nature for some wise purpose. Many thousands of Rose seeds have been destroyed by allowing the pods to become as dry as chips. I remember seeing on one occasion a bushel of foreign seed quite spoilt in this way. As the seeds are picked out lay three on the surface of the soil and push them down with the blunt end of a lead pencil to a depth of half an inch. Cover the surface with sand and duly record the cross on a label, and when several pots are sown give a watering with a can having a fine rose.

Stand the pots on slates or shingle as near the glass as possible. Gently spray over the surface of the soil in the pots with a fine syringe each bright morning. By March the seedlings will begin to appear, and they will need careful watching and especially to remove with a camel hair brush any drops of water that lodge on the tiny leaves after spraying. Have some compost such as is recommended above in the house in readiness and a number of clean thumb pots. As soon as the seedling appears take a sharp label and push it into the soil and lift out the seedling and pot it off into a thumb pot, placing the latter inside a larger pot to shield it from drying too rapidly. Be careful not to break the tip of the root. If lifted and potted before making a leaf the plantlet will not flag at all. When a few inches high it should be potted on into small 60's, then into large 60's, and later into 48's. Place the pots as near the glass as possible. Harden off in June, and plant outdoors in July, unless house room can be found for them which is much the best, and is the method adopted by all practical raisers. By the autumn they will be quite strong plants and some will bloom. Buds may be secured of some of the strongest even the first year. Good ripe buds are then obtained which may be budded on briars in the open ground or on potted-up briars; if the novice hesitates to pot off the seedlings, they may be kept in the seed pot and potted on later, even if only one seed has germinated.

It is very essential to secure a bud or two, although very tiny. I have put them on to half-standard briars, the buds having the wood retained. If the amateur is not used to budding he should call in the aid of an expert. The plant often will die after it has flowered. I have saved some beautiful seedlings by budding as advised above, while the little seedling plants have died in their first year.

Do not discard the seed pots for over a year as frequently some of the seeds will take twelve months ere they germinate.

When I raised Juliet, which was obtained by crossing Captain Hayward with Soleil d'Or, the plant flowered in the pot it was raised in (a 48 size) with two other seedlings from the same cross which proved worthless. The seed was sown in January, 1906, and the plants were grown in pots under glass all that year. In March, 1907, the seedling plant blossomed. Grafts were taken from the plant and by the autumn about 50 plants were obtained which yielded buds that were budded the same year, and grafts the following winter. I have sown in one season as many as 2,000 seeds, all obtained by crossing, and they represented some 130 distinct crosses. I could give details of the various crosses I have made, but will content myself by recording a few that have produced what will be very popular Roses, although at present some are not named. Each hybridist must strike out a line for himself. We want new breaks such as Mr. George Laing Paul has given us in his lovely little dwarf Perpetual wichuraiana Roses. I would suggest that the latest results of the most celebrated raisers be utilised as seed and pollen parents. Although I know most raisers have their own special strain, yet if we work upon their most recent introductions then we reap, to a large extent, the benefit of their labours. There is a wide field for the amateur, and the more who take up the work the better it will be for our favourite flower, and if gold medal Roses are rarely obtained many delightful and original forms may be raised for one's own pleasure.

Compound crosses should be carried out. That is by crossing two sorts together, then cross the seedling with the seedling of another cross. This was how Conrad F. Meyer, Gruss an Teplitz, and that lovely gem, Gottfried Keller, were obtained.

I would suggest that the Lyon Rose be freely employed as a pollen parent, for as a rule it is the pollen parent that gives colouring. Then there are such distinct sorts as Arthur R. Goodwin and Entente Cordiale (Guillot), André Gamon, Duchess of Wellington, &c., that would be lovely from a colour point of view. Remember it is not always from Show Roses that one obtains seedling Show Roses. Far from it. I have raised from K. A. Victoria quite worthless seedlings, whilst from the almost single-flowered Corallina I have raised a flower so double that it would not expand. Whatever object is aimed at, be prepared for very many disappointments, but by crossing a large number of blooms, some good novelties, are sure to follow. That grand Rose, Earl of Warwick, was raised by crossing Souvenir de S. A. Prince with Mrs. W. J. Grant, and the cross was made by the son of the late Henry Bennett when engaged at Waltham Cross. Cynthia I raised by crossing Frau Karl Druschki with Paul Lédé, and a very beautiful rambler named Elsie was the progeny of Blush Rambler crossed with Jersey Beauty. Fairy I raised from a self-fertilised flower of Perpetual Thalia, and Margaret was raised by crossing Mme. Lambard with Caroline Testout. Amateurs should take courage and go in for Rose raising. It was an amateur, Mr. Postans, who raised Lord Bacon, from which Mr. Hugh Dickson evolved Hugh Dickson, crossed, I believe, with Gruss an Teplitz. I could give numbers of crosses that have produced glorious Roses, many not yet in commerce, but each amateur must use his own discretion, and try and break fresh ground.

I believe from nearly every variety pollen may be obtained, so I need not name any specially, but a few good seed bearing kinds are Antoine Rivoire, Mme. Abel Chatenay, Pharisaër, Joseph Hill, Frau Karl Druschki, Mme. Edmée Metz, Mme. Ravary, Paul Lédé, Le Progrés, Gustav Grunerwald, Laurent Carle, Killarney, Earl of Warwick, Caroline Testout, White Lady, K. A. Victoria, Mme. Lambard, Souv. de Wm. Robinson, Richmond, Mme. Mélanie Soupert, Warrior, Mme. Gamon, Captain Hayward, Mrs. J. Laing, Mme. Jean Dupuy, Betty, General McArthur, G. Nabonnand, Farben Koenigin, K. A. Victoria, Lady Battersea, Etoile du France, Mme. Hoste, Corallina, White Lady. Lady Roberts, Lady Mary Fitzwilliam, Prince de Bulgarie, Instituteur Sirdey, Marie Van Houtte, Countess of Caledon, Mme. Segond Weber, Dr. Grill, Marquise Litta, Mme. Berkeley, President, Souvenir d'un Ami, Beryl, Souvenir de Pierre Notting, &c. From all of these I have obtained good seed after crossing with various varieties.

To those who would wish to pursue the subject on a more scientific basis I would refer them to the Journals of the Royal Horticultural Society, where some excellent material has been gathered together from which the student would derive much valuable information.

1906 Report of Third International Conference on Genetics.

Then, in addition, those who possess the Rosarian's Year-Books for 1892 and 1896, will find some inspiring thoughts by the late and much esteemed Lord Penzance.