The greenhouse favourites grown from cuttings are in themselves enough to keep every greenhouse full of bloom all the year round, as well as providing a special hobby for a wide variety of people.
The actual process of taking cuttings has been revolutionised in recent years for the less skilled. Hormone rooting powders hasten rooting and make difficult species easier to strike, while the plastic bag has created a simple way of ensuring a moist environment for a potful of cuttings until rooting takes place. Mist propagation is a sophisticated option, but it is a luxury for those who do not need to raise many plants.
Although there will always be room for judgement and experience in the choice and timing of difficult cuttings, the miracle of reproducing an exact replica of an admired plant at will from a small piece is open to all.
In general terms it is the vigorous young shoot, which has not yet reached the point of flowering or ripened its wood, that roots most readily. There are green tip cuttings, semi-ripe cuttings and hardwood cuttings, as well as leaf and root cuttings, but the favourite greenhouse plants in this chapter are increased by young shoots. These need to be neatly severed, with a sharp knife or razor blade, just beneath the node or joint and put into their rooting medium while still crisp and fresh.
The compost for cuttings should hold moisture yet drain freely, and there are many alternatives. The John Innes formula is 1 part loam, 2 parts granulated peat and 3 parts coarse sand, all measured in bulk. Peat and sand in equal proportions is a much favoured mixture, while peat and sand, vermiculite or perlite are often used. Under mist pure sand is satisfactory, and it can be used without mist so long as it never dries. For cuttings that are not going to be potted up separately as soon as they have rooted, equal parts of loam, peat and sand provide more nutriment; and equal quantities of John Innes potting compost and sand is yet another alternative.
In any case the moisture of air and soil round the cuttings must never fail before they are rooted. Then they are gradually exposed to the air, first by opening and subsequently by removing the plastic bag or other covering.
In order to create enough plants for a group of ground cover in the garden, and for replacement of tender shrubs liable to be killed in a hard winter, some propagation is essential. Also, kind friends offer cuttings, for which unexpected gift the keen gardener is always ready with a plastic bag to take them home without wilting.
A majority of greenhouse plants are propagated from cuttings, and there are four favourites which for many are the principal purpose and pleasure of a greenhouse.
Perpetual flowering carnations are irresistible to some and merely a curiosity to others. The necessity here is to have healthy virus-free plants and not to keep them for more than two years. There are specialist nurserymen raising virus-free stock: they will often give advice to the beginner. Little heat is needed, but plenty of air and good winter light are essential. There needs to be room for the plants to grow tall, and red spider must be effectively controlled. A minimum winter temperature of 7°C (45° F) is desirable, as winter is the principal flowering season and cut flowers the main purpose. Cuttings can be rooted from November to March, and spring is the time to buy rooted cuttings to start a collection.
Chrysanthemums are the favourite flower of countless enthusiasts in temperate climates, as well as a major horticultural and artistic preoccupation in Japan. There is a good basis for such universal acclaim, for not only is there a great variety of flower size and type from which to choose but a spectacular response to skilled cultivation and training. Chrysanthemums also brighten the dark days of our autumn and early winter and provide exotic forms for flower arrangement.
Clearing out the greenhouse completely in summer and replacing the large plants with fresh young cuttings full of promise each spring are two aspects of chrysanthemum growing that appeal to many. Cuttings root at 7°C (45°C) and high temperatures are never needed. Healthy stock is important here too.
The fuchsia is no less adaptable in the variety of ways in which it can be trained and grown and also responds to skill in cultivation. The flowering season of fuchsias can be increased by the manipulation of daylength, as is done with chrysanthemums. As they naturally have a very long flowering season and cuttings strike easily at almost any time of year, there is no need for the amateur to fuss with extra lighting. Longer days induce flower buds to form, whereas the chrysanthemum is a short-day plant that has to be blacked out in the summer to initiate flowering.
Where there is little heat or space, fuchsias can be overwintered by allowing them to become dormant in autumn, when watering is gradually reduced so that leaves fall and the wood ripens. They can take three to four months complete rest, but the root ball should be neither frozen nor dust dry during this time.
They are then cut back and started into growth in February- or March. Autumn cuttings, or young plants being grown as standards, have to be kept growing through the winter, for which at least 7°C (45°F) is needed and 10°C [5G°FJ preferred.
Again skill in cultivation brings great rewards. A poorly grown fuchsia is a poor thing indeed. A neutral or lime-free soil, and plenty of judicious feeding, and well-timed training are essential for real success. The plants are attractive to white fly but otherwise reasonably healthy. A constant stream of new cultivars, as well as the very large selection of established varieties, means that there is an overwhelming choice.
Perhaps the most universal favourite of the unskilled as well as the specialist is the geranium, more properly called the zonal pelargonium. Since its first fashionable success in Victorian times, the pelargoniums have been greatly developed and also new species discovered.
Today there is something for everyone and a flow of new cultivars from the United States and Australia as well as Europe. The regal or show pelargoniums, flowering mainly from April to June, can be huge bushy plants with magnificent velvety flowers for the decoration of spacious places. Fortunately even more floriferous and adaptable dwarf regals have been created and there are a few miniatures. But all can be grown to a modest size, if confined to fairly small pots and renewed yearly from cuttings.
Zonal pelargoniums have been produced in such enormous numbers and brilliant colours for summer bedding, that not everyone realises the scope of the many kinds which, though they would not make a show in the open in one of our wet summers, are nevertheless good greenhouse and conservatory plants. A visit to a geranium nursery can be a revelation. There are even specialists in the miniature forms, and no greenhouse is too small to have a fascinating collection.
In recent years bedding geraniums that are raised from seed each year have been so much improved that they are often preferred for municipal bedding. These are usually raised in heat very early in the year and treated with hormone dwarfing agents to encourage early flowers and a better shape. The seed is costly and should have a temperature of 18°C (65°F) to germinate. They take much more water than the old geraniums and will not flower before July if conditions are poor. They respond well to automatic watering. All members of this family are very easily increased by cuttings, which need 7°C (45°FJ to over-winter happily but survive much abuse.
As with so many plants constantly renewed from cuttings, there is much virus-infected stock, which is why seed-raised plants have become popular, otherwise they are healthy and long-suffering given sufficient ventilation and freedom from frost. The danger of spreading virus infection has led the professionals to dispense with the knife when taking cuttings, but amateurs can use discarded razor blades or sterilise the knife between each cutting if there are only a few. Zonal pelargoniums are among the few cuttings best left uncovered for rooting, but as with all cuttings there must be shade from direct sunshine.
To produce a shapely pot plant with plenty of flowering shoots usually requires encouraging the early development of side shoots, and sometimes the prevention of flowering before maturity for the best results.
"Nip out the growing point at 6 inches high" is a frequent instruction in horticulture and could be applied to any of the plants I have mentioned. However, so much thought has been given to the accurate timing of chrysanthemum blooms for show and to disbudding to increase their size, that any serious grower will follow a much more elaborate regime than I could detail here.
The training of woody pot plants is an art that has largely been lost in the last hundred years and can be learnt only by practice and example. In a small greenhouse or conservatory there would be room only for one or two elaborately trained specimen plants, and the emphasis must be on young plants and those that are naturally compact in growth.
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