The appearance of a healthy flower is due to its inherited characteristics, and these are determined by the genes carried by the chromosomes in its cells. Each gene is responsible for a certain feature of the plant such as its flower colour, shape, size, the height of the plant, the texture of the leaves, the time of flowering and so on. Some genes are dominant over others, and when they are present the features governed by them will always appear, although there may be latent possibilities of different characteristics.

When cross-pollination takes place between two plants, the genes carried in the reproductive cells sometimes become rearranged in the chromosomes, and by pure chance one chromosome may get a double amount of a normally recessive gene. A seedling carrying this chromosome in its .cells would in such a case differ noticeably from its parents. It might grow unusually large, or have double flowers instead of single ones, or have petals of a different colour. In nature, odd freaks or so-called mutants like this are apt to disappear again, because unless they are self fertile or receive pollen from a similar freak plant, all their seedlings will revert to normal.

When plants are grown in gardens, new forms are immediately noticed. If they are better than their parents they will be cherished and isolated, and then deliberately bred or propagated from cuttings so as to perpetuate a new and desirable characteristic. Over the years the great majority of garden plants have been improved by selection, cross-breeding and hybridizing, and so new strains have been produced which have greater decorative value than the original wild forms. Gardeners today owe an immense debt to the Chinese, because it was they who began developing flower growing as an art many centuries before anybody else. When the chrysanthemum, the paeony and the camellia arrived in the West, they were already very sophisticated plants which had been bred for so many years that a large number of different varieties had been obtained.

Cultivation of the chrysanthemum in China goes back nearly 25 centuries to 500 BC. The garden chrysanthemum is a hybrid, whether deliberately produced or accidental it is not possible to say. However its two ancestors were most likely the yellow Chrysanthemum indicum and Chrysanthemum morifolium which has either white or purple flowers. Their progeny has been named Chrysanthemum hortorum, which makes it quite clear that it is a garden plant, and in the skilled hands of gardeners, both in China and later on in Japan, it has given rise to an apparently endless succession of new forms, which are still being improved. This universally popular flower has only been grown in Europe since 1789, but became a favourite so quickly that fifty years after its introduction, over a hundred different varieties were already being grown in England. It can now be brought into bloom all through the year.

The paeony occurs wild in Europe and in many parts of Asia, including Siberia, but once again it was the Chinese who first appreciated it as a garden flower and began to select and breed it. The wild white Asiatic paeony, Paeonia lactiflora, was first mentioned in Chinese literature during the 5^th century BC, and a few hundred years later the tree paeony or moutan also came into fashion in China where it was cultivated to high perfection. The yellow form was especially sought after, and high prices were paid for plants or even for single flowers. The western nations lagged far behind and did not begin to develop paeonies until the eighteenth century when the first few Asiatic plants were imported.

The ancestry of garden roses is now impossible to unravel but we do know for certain that one of the forebears was Rosa gallica. It is likely that this red rose was brought into Europe by the Persians who had been keen rose growers for hundreds of years before they invaded the west. It was the semi-double form of Rosa gallica which was later chosen as an emblem by the house of Lancaster, while the white rose of York was Rosa alba, a very old hybrid whose parentage is unknown. Rosa moschata is an autumn flowering white rose whose modern descendants are known as musk roses. Rosa moschata now seems to have disappeared in the wild, but it too was grown in ancient Persia, so its homeland was probably somewhere in the Middle East.

The early roses bred in Europe all had a comparatively brief flowering season. The long flowering habit of modern roses was derived from a mutation of the Chinese rose, Rosa chinensis. In its original wild form this was a climbing rose with a short season. In cultivation it produced a sport, which was a shrub instead of a climber, and which flowered continually through the summer. It came to Europe, probably by way of Persia, in the sixteenth century. Another freak rose which also first appeared in China was the tea rose, Rosa gigantea. The first variety of this to arrive in Europe was known as the pale China rose and it flowered for the first time in England in 1793. It was the hybrids between these two sports which became the ancestors of the vast majority of modern garden roses. Serious European rose breeding first started in France and many roses still bear French names. The Empress Josephine, Napoleon’s first wife, established a large collection of roses at Malmaison. Although the so-called old-fashioned roses are not as floriferous over a long period as the modern varieties, they have such a charming scent and are so lovely that many discerning gardeners still appreciate them.

The development of the modern garden lupin from wild American species is a story of the present century that was only completed just before the Second World War. The man who brought all the gorgeous colours and combinations of colour into lupins was George Russell, an Englishman, and it took him twenty-five years to achieve what he wanted. He did not use deliberate hand-pollinating methods, but simply planted Lupinus polyphyllus, which has blue, white and pink forms, in close proximity to the yellow tree lupins, also including in his collection some colourful annual Mexican species. Wild bees did the rest and every year when his latest crop of seedlings flowered, George Russell ruthlessly destroyed all plants which did not show an improvement or a new colour combination. The good plants were retained, and this process went on year after year with only very gradual improvement. Fifteen years after he had begun his work there was a sudden leap forward with new and spectacular colour breaks appearing, and from then on the annual improvement of the strain became very noticeable. In 1937 when these lupins were first exhibited to the public they caused a sensation, and their glorious rainbow colourings put all other lupins in the shade. Russell lupins have now completely replaced all the older strains and although they do not come true from seed, the best named varieties are propagated commercially from cuttings.

Delphinium

Family Ranunculaceae

No other plants can really rival the large delphiniums for stately beauty, but they are demanding plants to grow, and need a deep rich soil and secure staking to give of their best. Delphiniums have been in cultivation since the days of ancient Egypt and it is not known for certain how the early garden forms were derived. They undoubtedly have Asiatic parentage, although wild species are found also in North America and in Africa. Most of the wild delphiniums are some shade of blue or violet, but there are also four yellow species including D. zalil from Persia and two scarlet ones, D. nudicaule and D. cardinale in California. Many of the wild blue delphiniums produce white forms from time to time, especially D. formasanum from the Caucasus. The massive compact spikes of modern delphiniums are the result of years of painstaking breeding and selection.

The attempts during this century to bring in the red colouring from the Californian species has proved especially difficult, even when seedlings have been treated with colchicine to overcome problems of sterility. Most of this work has been done by Dr R A Legro of Wageningen in Holland and by 1962 he had succeeded in producing large flowered delphiniums in many shades of red, yellow and orange. He then went on to try and introduce the strong scent of the white African Delphinium leroyi with considerable success. There is little doubt that large, scented delphiniums in a big range of colours will be generally available to gardeners well before the end of this century.

Dahlia

Family Compositae

The Mexican dahlias were already improved garden plants when Vincente Cervantes, who was in charge of the botanic garden in Mexico City, first sent them in the form of seeds to his friend Abbe Cavanilles in Madrid in 1789. They were intended to be used for food, rather in the manner of potatoes, but few people liked the flavour of the tubers. The dahlia would then probably have been completely neglected in Europe if the Empress Josephine had not taken a fancy to the flowers and started to grow them in her garden at Malmaison. Since that time dahlias have undergone such a change that neither the Abbe Cavanilles, nor the Swedish botanist Andreas Dahl after whom they were named, could recognize them any longer. From being a vegetable, the dahlia has become the queen of the late summer flower garden in all its colourful variety and a favourite for the show bench.

‘Peace’ Family Rosaceae

Many people think that ‘Peace’ is the greatest rose of this century. It was raised by F Meilland at his rose nursery on Cap Antibes in the South of France and received its first Gold Medal in the USA in 1944, followed by four more top-class awards in the next three years. It is an exceptionally vigorous and healthy rose which should not be hard pruned. The flowers are large and full, but their delicate colouring saves them from looking heavy and they stand up well to bad weather. It is not powerfully scented, but its many other good qualities make up for this.

Bearded iris

Family Iridaceae

The most widely grown and beautiful of all the cultivated irises are the tall bearded forms which have a wider range of colouring than almost any other garden flowers. They are not, as is often said, descendants of the European Iris germanica, for it is a sterile plant. In fact they have arisen from hybrids between Iris pallida and Iris variegata, both of which are found round the Adriatic and even hybridize in the wild. The first growers to start selecting seedlings of these irises at the beginning of the nineteenth century were a German, E von Berg, and a Frenchman named de Bure. They were followed by others, notably M Lemon who continued to produce new cultivars steadily for more than fifteen years. Later on several English nurserymen like Peter Barr and Amos Perry also took up iris breeding. New varieties are still being raised and their popularity as garden plants continues. All these irises need good drainage and sunlight, and prefer a soil which is alkaline.

Hybrid lilies

Family Liliaceae

The wild lily species are such beautiful plants that the idea of improving them still further did not arouse much interest until the beginning of this century. One of the first lily breeders was Mrs R O Backhouse, who crossed Lilium hansonii with L. martagon to produce the Backhouse hybrids in the 1890s. North American lilies played a large part in the breeding of the vigorous turk’s cap type Bellingham hybrids which appeared in the 1930s and in recent years the most spectacular lilies have been the result of work done by Jan de Graaff in Oregon. His magnificent yellow trumpet lilies have been especially admired. The most famous of these was golden clarion, but many more have followed, including honeydew. The hybrid lilies are often easier to grow than many of the species, but they are also unfortunately very susceptible to virus disease. However it is possible that this tendency can be overcome by further breeding from resistant species.

Carnations and pinks

Family Caryophyllaceae

Dianthus caryophyllus, the ancestor of the carnation, is a rather small wild flower native to southern Europe and the Near East. It has also been naturalized in many parts of France including Normandy, as well as on old walls in England. The clove carnation is one of the really old garden flowers and has been cultivated in Europe for at least 2,000 years and probably longer than that in the East. The Greeks referred to it as the divine flower and in England, where it probably arrived with the Normans, it became known as sops in wine, or gilliflower. This is probably a derivation from the French geillet oiroflee. In Germany and Holland the flower is known as Nelke and in Sweden it is called nejlika.

The Dutch painter Jan van Eyck’s famous portrait ‘The man with the carnation’ painted about 1430, shows a serious looking gentleman in a fur hat and silver chain with cross and bell, holding a small red and white carnation in his right hand. The striping or mottling appeared quite early in cultivated carnations, and when the great Dutch flower painters depicted them in their splendid pictures they had become very much larger and more varied in colour. Carnation shows were held in Elizabethan times, but it was not until the beginning of the nineteenth century that the custom of improving the appearance of the flowers by ‘dressing’ began. Appropriately enough it was started by a hairdresser named Kit Nunn, and now competitors dress not only their carnations but their chrysanthemums as well as a matter of course, using much the same technique as is employed in arranging curls of hair.

The first long-flowering carnations were raised in Europe in 1750 and became known as remontants, but did not arouse much interest elsewhere until American breeders took over. They raised many new varieties including the famous Mrs S Lawson, a pure pink flower which became the parent of many later cultivars. There are carnations, so-called border carnations which can be grown successfully out of doors in Britain, and flowers for most of the summer.

Pinks have smaller flowers and form much more branching and compact plants than carnations proper. They are descended from Dianthus plumarius, another pink-flowered wild plant with the same distribution as D. caryophyllus. The most famous of them all is the strongly scented, snow-white double pink called Mrs Sinkins, which first appeared in the workhouse garden at Slough in about 1870 and was named after the master’s wife. It is still grown in many gardens today.

Tulip

Family Liliaceae

The rather stiff appearance of the tulip has always appealed to tidy gardeners, and the Dutch with their sense of order and preference for formal gardens, were just the right people to welcome and cherish this Turkish flower when it first reached Europe in 1554. Tulips were soon springing up in new forms and colours in the flat fertile fields of Holland and by 1634 people were in the grip of tulipomania. They used to spend ridiculous sums on single bulbs of new varieties, but in time the craze died down. Tulips are still grown in vast quantities though, and since the Second World War many previously unknown tulip species, with attractively patterned leaves, have been brought into cultivation.