Chapter 10 - Growing Roses Under Glass
There are few flowers that can be grown in a greenhouse which can give as much pleasure as the rose—nor one that will continue to do so for so long. A rose in a nine-inch pot can be made to give good service for anything up to ten years or more. Few other flowers can ever hope to compete in giving such lasting pleasure. Only those who have seen the glorious clean and healthy foliage and the superlatively beautiful blooms during the month of April can appreciate the joy of growing roses in a greenhouse. To be successful in their culture no elaborate house is required, nor an expensive heating apparatus. In fact, so accommodating is the rose, it has no objections to being in company with the many and varied subjects that the average amateur manages to squeeze into his greenhouse.
In districts where the air is so impure as to render the growing of roses in the open garden a very difficult matter, the protection that glass will afford in keeping the particles of soot off the foliage will make rose growing not only possible, but quite successful. I remember visiting a small garden in the industrial north where even the commonest plants were having a struggle to exist, and even rambler roses were very miserable, yet planted in a tiny greenhouse was a bush rose making such growth as to quickly grow out of its position. Were I condemned to live the rest of my life in a town, my only wish would be to have sufficient space for a greenhouse in which to grow roses.
In growing roses under glass there are several courses open to the beginner. Roses may be planted out in the soil in the normal way; they may be potted-up from the garden or nursery; stocks may be potted up and budded, or one may lift stocks after budding in November and pot them with the dormant bud in them. All of these methods can be completely successful, although the potting-up of stocks and budding them in the pots is the way to get the very best results.
The disadvantage of planting out is that it would mean having very little else in the house all the year round, which few people of moderate means could afford to do. The potting-up of plants I do not consider as satisfactory as either of the other methods owing to the difficulty of getting the right root system for potting. The majority of plants obtained from a nursery will have been budded on the seedling briar stock; as a stock for planting out in the soil there is nothing as good, but for pot work, one that has been grown from a cutting is the best for the purpose.
My own choice, and I think all amateurs who grow roses in pots would agree, is the rugosa, either as a dwarf or standard. My own greenhouse, which is of the lean-to type, makes it necessary to use the standard rugosa stock in order that the plants will be nearer the glass. It has other advantages such as ease of tending to their needs, top dressing and feeding. Why the rugosa stock is so much to be preferred to any other is that its roots are fibrous and it is able to fill the pot quickly with them. In that statement lies the whole crux of successful rose-growing in pots, and the reason why the method of potting-up stocks and budding in the pots is so desirable. The wild stock being so much quicker in growth than the rose, fills the pots with roots in one season, whereas a complete plant might take two seasons at least.
The lifting of stocks that have been budded the previous summer from the open ground, can give very good results, not because I have found it better than the method of budding them in pots, but merely to save the trouble of watering the stocks during the summer. Where all the garden work has to be done by one individual, matters of this kind have to be taken into consideration.
Planting out in the greenhouse
Although for reasons given, planting out in the greenhouse is not a convenient way of growing roses, there is no reason why at least one plant should not be grown without interfering with the general use of the greenhouse for other subjects. The most popular type of greenhouse to be found in the smaller gardens is the span-roof type. The size varies, but one of twelve feet by nine is fairly common. Such a house can accommodate one plant at the end opposite the entrance. There will probably be a staging running round three sides and if there is it would be necessary to grow a standard rose, planting it in the soil and allowing the stem to come through the staging. Wire can be stretched across the end of the house to train the rose as it grows. Such roses, when established, will give three crops of bloom during the year and will not interfere with any other plants that happen to be in the house. Choose a variety that is capable of good growth, preferably one that is fairly full, since those with few petals are rather fleeting in character; a rose like Peace, if yellow is desired, or Red Ensign, Josephine Bruce or Crimson Glory for crimson, McGredy's Pink, The Doctor, Pink Favorite for pink ones. For cutting, Lady Sylvia would be a good choice, although the blooms would not last as long as the others I have mentioned.
If for one reason or another it is not possible to plant the roses in the soil of the greenhouse, the difficulty can be overcome by building up a bed with bricks, breeze blocks, or concrete blocks. For the bed to be successful it should be not less than eighteen inches deep and should, if possible run the whole width of the house. The bottom of the bed should be deeply dug and well broken up to allow any surplus water to drain away. It should then be filled up with the best soil available and left to settle for a few days before planting the roses. Should this method be impracticable, a large barrel or tub could be used, although the ultimate result could hardly be expected to be as good, owing to the absence of a free root run. Then again the barrel or tub would not have the permanence of the bricks or concrete. The whole idea of giving the plant as much room as possible in which to grow is so that it may be induced to develop a climbing habit which it will do if it is allowed to grow freely. I have three plants occupying the wall of my greenhouse, a space of thirty feet by twelve, and the problem is what to do with all the growth, in spite of its being cut back twice a year. Incidentally two of the roses are varieties which do not grow well with me in the open garden—Miss Willmott, an old cream rose, and McGredy's Yellow. It is eight years since the last-named was planted, and I have counted as many as eighty blooms at its first flowering in the spring, and during the summer one can often see blooms poking out of the ventilators.
Do not plant climbing Hybrid Teas, for the terrific vigor that these roses have when planted under glass is overwhelming, and so much growth must be cut away in order to keep them within bounds that nearly all the bloom is pruned away. If the ordinary Hybrid Tea is used no non-flowering growth is made and the plants can be kept to reasonable proportions without sacrificing very much bloom. Of course, one cannot plant such a rose and expect it to cover all the available space in a year or two, but the plants bloom freely and increase in stature each year.
The treatment is rather different from that given to roses in pots or those grown in the open garden. We want to induce the plant to climb, and it does this by ripening its growth, so that each year the growth is extending. It will be found that there is little tendency to produce basal shoots, such as there is with the same plants in the garden, and it is very possible that the wood that is on the rose when first planted will be there after many years. By this we can see the importance of getting a plant with its growth well placed. That is why it would pay handsomely to visit the nursery and select one's own plant. One on the rugosa stock would be best, and also one that is budded in one place, having three or four growths to form a fan. The nurseryman will be only too happy to oblige, since standard roses budded in one place sell badly as a rule, although they should not do so, for they grow equally as well as those that have been budded in three places.
Having procured a suitable plant, the growth should be shortened back to about a foot and any weak or soft growth removed; and see that there is no snag on the stem at the point where the rose growth emerges. If there is, pare it off neatly with a sharp knife so that in a year or so the cut will be healed over, thus prolonging the life of the plant.
In planting, the soil should be well dug and some good turf material mixed in; also some hoof and horn and bone meal. If there is some well-rotted farmyard manure to add, so much the better, as long as it is mixed with the soil and not put underneath the plant. After planting, the staging can be put back in its original position. The plant should not require any further pruning and the subsequent treatment consists in inducing as much growth as possible by frequent spraying during sunny weather, and tying in to wire supports as much of the new growth as possible. It is unwise to cut the blooms as they come, with long stems; cut blooms by all means, but in doing so do not remove too much foliage. When the plant is making good growth it will not object to being cut about, but it will when it is building up its structure.
I have dwelt on this subject rather at length, but I believe that to have a rose doing well in the greenhouse is a real joy, not merely for a little while but for many years.
Roses in pots
Although the growing of roses in pots does not present many difficulties, they do not more or less look after themselves as do those planted out in the soil. Furthermore they do not produce large quantities of bloom, which is quite natural in the restricted space of a pot. What one does get, however, is a much finer bloom, and the advantage of their mobility.
There are three methods of growing roses in pots. They may be purchased and potted-up; stocks may be potted and budded the following July, or they may be budded in the garden and lifted and potted with the dormant buds. All three methods are practicable, but the best of all is to pot up stocks and bud them in the pots. The most important thing is to get the pot full of roots before any forcing takes place, and since the wild stock is more vigorous than the average hybrid rose, an established plant is obtained in so much less time. The stock that I favour for the purpose is the rugosa, which, being fibrous rooted is well suited for pot work.
In the past a great deal of importance was placed on the preparation of the soil for potting roses, but now, thanks to the adoption of the John Innes compost, the whole business is simplified. It must be realized, however, that not all potting composts that go under that name are as good as one another, because the value of the compost depends upon the quality of its ingredients, such as the loam, peat and sand, although there should be little variation if the formulae are strictly adhered to, using the grades of materials specified by the original workers. There are quite a number of firms who make a speciality of producing this compost and I should strongly advise the purchase of it from those sources. There are three potting composts, each varying in the amount of fertilizers they contain. JI.P2 contains double quantities of fertilizer and chalk and JI.P3 has a treble dose of fertilizer and chalk compared with JI.PI.
The task of potting should be carried out about the middle of October. If the plants to be potted have to be purchased, the nurseryman will have to be notified of the need to send the plants before the usual orders are executed. It is very essential that plants intended for potting should be of the best quality. To pot up small, weak plants is to invite disappointment. The best size of pot for the purpose is one nine inches across the rim. A size smaller may be used, but the plants are apt to get very root-bound in a year or so. Naturally one will start off with clean pots, even if they do not remain in that condition long. Over the drainage hole place one large crock and over that about an inch of smaller ones, for it is very important that the water should drain away freely. A few pieces of turfy soil or a handful of coarse peat, placed over the crocks will prevent the soil choking up the drainage. Now put some soil in the pot so that it will be about half full and ram it fairly firm with a potting stick (a piece of broom-handle serves the purpose quite well). Then try the plant in the pot to see whether it is possible for the roots to be contained, at the same time leaving the point where the rose and stock join about an inch below the rim of the pot. This may entail either putting some more soil at the bottom of the pot, or taking some out. Assuming the depth is correct, have a shovelful of soil ready to hand, pressing the roots down at the same time. When all are in position, add the soil, rocking the pot so that it falls into position; ram again until firm and add the rest of the soil, which can be pressed down with the hands. Allow one inch below the rim of the pot so that an adequate amount of water can be given. After potting, the plants should be placed close together in a sheltered spot, and can stand on tiles or ashes so that worms cannot get into the pots and choke the drainage. There is no need to water the plants, since there is usually more than enough rain for the purpose.
The pots should be brought into the greenhouse about the end of the year, coinciding with the removal of the chrysanthemums. If, however, the greenhouse is unoccupied, they could be brought in a month earlier, but such a practice would only be advantageous in the event of severe weather, when soil in the pots might become frozen, thereby giving the newly-potted plants a setback.
On housing the plants no heat should be given that would be likely to start the plants into growth; in fact the principle to work on should be to imitate the kind of weather conditions that might prevail from March to June in the open. With the present price of fuel as the limiting factor, it is hardly likely that the roses would be unduly forced.
After housing the plants they should be pruned. The pruning of roses in pots should be drastic, for it is rare to have more than two growths from a cut-back stem, so that if the pruning is done with a light hand, a leggy plant will result. It is very necessary to prune to an outside bud so that a symmetrical plant will be obtained, much more so than plants grown in the open ground where several basal growths are produced.
Roses that have been potted up in the autumn should have cool treatment from the beginning, and with such treatment they can be expected to be in bloom by the first week in May. Those that have been budded in the pots, and are therefore established, can, by applying a moderate amount of heat, be brought into bloom a month earlier. Rugosa stocks that have been budded in the open ground and have been lifted and potted can be treated similarly to those that were budded in the pots, since they will be found to have an enormous root system when lifted and will quickly establish themselves in the pots. Heading back the wild growth to the dormant buds should take place at the same time as pruning.
Except for the established plants, no feeding should be done while they are in the greenhouse. For those that are established a liquid manure made from any of the proprietary complete fertilizers should be applied once a week when the buds are first seen, until the blooms show color. Most growers of roses in pots have their own special feeding mixtures, but as they are all made up of nitrogen, phosphates and potash in various forms, as far as my experience has taught me, there is very little to choose between them.
The great thing in achieving success in growing roses in pots is having the correct buoyant air conditions as afforded by correct ventilation, and attention to spraying the plants with clear water whenever the weather is bright enough. In dull weather, such as we sometimes experience in March, with a north-east wind blowing, it would be wise to close the ventilators and withhold watering and spraying until more genial weather prevails.
Aphides are sure to put in an appearance sooner or later; fortunately they are very easily dealt with by fumigating with nicotine or spraying with malathion. It is best to do this as soon as the pests are noticed, and not leave it until the plants begin to suffer.
Red spider is a much worse enemy than aphis, for it is often not noticed until it is firmly established. Here again we are fortunate enough to have a good remedy in the form of azobenzene smokes, which operate in the same way as nicotine fumigants. There are full instructions given with these articles and they are sold by nearly all horticultural sundriesmen.
Rose mildew may put in an appearance, especially if sufficient attention has not been given to ventilation, for to allow the greenhouse to become overheated by sun, and then to let in a draught of cold air through door or ventilator, is a certain method of encouraging the disease. Where the greenhouse is heated by boiler and pipes, a little sulphur rubbed on the top pipes should be sufficient to keep mildew down to a minimum.
It will be found advantageous to have some kind of shading material, for, in bright sunshine in March, the young and tender foliage is, especially in some varieties, likely to be scorched. Failing that, a cheap and effective way is to mix some whitening with water thinly, and spray it over the outside of the glass, sufficiently to shade the roses. This may have to be repeated if the whitening is washed off by heavy rain, but it will be found to be less trouble than other forms of shading unless one has blinds fitted that can be adjusted easily.
At the beginning of June the plants will be removed from the house, for by then the roses in the garden will have claimed our interest. The plants should stand out in an open position near a tank so that watering is not likely to be neglected. An occasional feeding with some weak manure water will help to build up their vigor. If the watering during the summer is likely to be a problem owing to absence during the holidays, the plants may be taken out of the pots without disturbance and planted in the garden until the autumn, when they may be repotted. This is a practice I have followed for some time, and the results have been quite satisfactory. When repotting, as much of the soil as possible at the top of the roots should be removed and replaced with fresh soil; this applies whether they have been removed from the pots or not.
Choosing varieties for the greenhouse
In making a choice of varieties for growing in the greenhouse, it is best to choose those that have a greater number of petals, for not only do such roses grow to perfection with the kindly protection that the glass affords, but, what is very important, they last so much longer. Here are a few which I believe should satisfy all tastes and have good lasting qualities. Dame Edith Helen—a real beauty; William Harvey—a rose that retains its form longer than almost any other; Red Ensign—another good crimson with a very powerful scent; William Moore—a pink rose of grand form; Peace—very good in the garden and superb in the greenhouse; Sir Henry Segrave —pale yellow, lovely elegant buds; Percy Izzard—a very large cream with a deep centre, a poor garden rose but excellent inside; Madame Joseph Perraud—under glass one of the most beautiful roses, with shades of orange and salmon; Mrs. Charles Lamplough and McGredy's Ivory—two roses of similar colour with different petal formation, and it would be difficult to know which one to choose if a choice had to be made; Julien Potin—the best pure yellow and one well suited for the purpose; Glory of Rome—with its brilliant cerise-red blooms is one that should always be included.
This by no means exhausts all the suitable varieties that could be selected for growing in the greenhouse. It is a matter of choosing the type of bloom required. The growth of the plant is of very little consequence as nearly all roses will grow fairly well under glass, even those that are an utter failure when grown in the garden.
If one should have a structure large enough to accommodate tall plants, many of the Rambler roses are quite easy to grow and make very handsome specimen plants for the conservatory. Strong two-year-old plants, lifted and potted, could be flowering the following year in a cool house, and could be forced earlier the next year if so desired. Those varieties with pliable growths are the best for the purpose, because the growths can be wound round four canes placed on the outside of the pot, and secured with a few ties. Lady Gay, Lady Godiva, Excelsa, Dorothy Perkins and Sander's White would be suitable.
Then there are the Dwarf Polyantha roses which are delightful greenhouse subjects. I like these best when grown as dwarf standards, although they are quite suitable for any height usual for standards. The Floribunda roses, too, could be relied on to give a gay display for very little trouble. I have found Sarabande particularly fine. Donald Prior and Dusky Maiden are both good. The growth of Frensham is, I am afraid, likely to be embarrassing. Pinnochio is very lovely, as is Independence, with it extraordinary orange coloring, adding to the interest of greenhouse roses.
There is a desire with many greenhouse owners to grow that old rose Maréchal Niel. I grew a plant of it some years ago and it gave me very little trouble. It seems to prefer a half-standard briar stock, rather than a dwarf. The blooms are rather pendulous, so that it is a variety suitable for training over the roof of the house. The blooms look very beautiful as they hang away from the glass. It is a poor rose for cutting, unless one cares to go to the trouble of wiring each bloom. The best blooms are borne on the new growths and pruning consists in cutting out the older wood and retaining as much new growth as possible. Short lateral growth should be cut back to an inch or two from the older wood. This should be done at the end of the year. Although it can be grown in a large pot, a rose of the habit of Marechal Niel is far better grown in the soil of the greenhouse, so that one can be more or less assured of a supply of new growth each year. Let me say at once that unless one is prepared to go to the trouble of growing it really well, one would be well advised to grow instead one of the modern yellow roses, such as Dorothy Peach or McGredy's Yellow.
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