Ornamental plants

1 Present diversity of ornamental plants in China

2 Threats to and destruction of Chinese ornamental diversity

3 Protection and continuous utilization of Chinese ornamental plant diversity

China has a long history in the cultivation of ornamental plants. As early as the 11th-7th century B. C. during the West Zhou Dynasty, in an ancient book Zhou Li· Tian Guan·Da Zai, there is a description that “herbs and woody plants are cultivated in gardens”. This shows that during that period our ancestors began to cultivate ornamental plants in gardens. “Zhou Li” also stated that “during the Zhou Dynasty, there are official gardeners, including Zhong Shi four men, Xia Shi eight men, Fu two men, Xu eight men, Tu eighty men”—responsible for raising birds, animals, fishes, worms and insects as well as ornamental plants. Therefore, China has over 2,000 years of history in growing ornamental plants. Owing to the abundance of ornamental germplasm resources, beginning from the 16th century, many foreign botanists and plant collectors came to China to collect them, and China was praised by some westerners as the “mother of gardens” (E. H. Wilson, 1929). China’s ornamental plants can today be found in many countries. For example, 70% of the ornamentals in California, U.S.A., came from China. Italy has introduced about 1,000 ornamental plants from China; England and Japan have also introduced many Chinese ornamentals. Fifty percent of the ornamentals now planted in Germany originated from China, and 40% of the Dutch ornamentals have been introduced form China. Indeed, Chinese ornamental plants, with their abundant genetic resources, have made important contributions to world gardens and parks either in direct planting or by being used as breeding materials.

1 Present diversity of ornamental plants in China

Ornamental plant resources in the world are abundant, with approximately 30,000 species. Of these, 6,000 are more commonly-used species with over 400,000 cultivars. There are about 10,000~20,000 species of ornamental plants indigenous to China. Among them, some 2,000 are commonly used. China is the origin centre of many precious garden plants, such as Prunus mume, Paeonia suffruticosa, P. lactiflora, Dendranthema mongolium, Lilium spp. Camellia spp., Rosa spp., R. rugosa, Magnolia spp., Rhododendron simsii and Davidia involucrata. China not only has abundant native ornamental species, and of good quality, but also has various famous flowers cultivars and their wild relatives, that is, their genetic diversity is outstanding.

Genetic diversities of Chinese ornamentals are mainly expressed as diversity in terms of plant species, diversity in species origins, and diversity of cultivars.

A. Diversity of Chinese ornamental plant species

Of the ornamental plants, China possesses many genera with numerous species. Thirty genera, with 2,238 species, are important ornamentals as shown in Tabel 1.

B. Diversity of Ornamental Plants Origins

The many origins of ornamental species are complicated, i. e., some were created by crossing two or more wild species the result of chromosome doubling (autopolyploids or, mostly, allopolyploids), or even more so the resulting complex of the above-mentioned causes. Thus, the origin of ornamental plants is so various and complicated that some are still a puzzle and undetermined. For example, the Tea rose (Rosa×odorata) is the natural interspecific hybrid of Rosa gigantea and cultivated R. chinensis; Garden petunia (Pharbitis×hybrida) is the interspecific hybrid of P. integri folia (2x=14) and P. axillaris (2x=14), the diploid hybrid then becoming changed to a series of polyploids by means of breeding and selection (3x=21, 4x=28, 5x=35,…). Furthermore, it is now known that the Garden chrysanthemum (Dendranthema×grandiflorum) originated in Anhui or neighbouring provinces during the 4th century, being a natural interspecific hybrid between D. vestitum and D. indicum at first. Later, D. zawadskii and probably other species were further crossed with the hybrid. After appropriate cultivation and successive selections, Garden chrysanthemum emerged. The number of chromosomes of Chrysanthemum cultivars varies widely, showing evolutionary differences between different series, groups, forms and cultivars. For example, the Small Chrysanthemum Series with D. indicum as its predominant constituent-origin species is having cultivars. With chromosomes 2n=36~56, while the Medium-Large Chrysanthemum Series with D. vestitum as its predominant constituent-origin species having cultivars. With chromosomes 2n=52~71. The constituent-origin composition is the first level criterion for classifying flower cultivars and it expresses the notable difference in flower size.

C. Diversity of ornamental plant cultivars

China is famous for her diversity of ornamental species cultivars, especially many famous flowers. For example, the Garden chrysanthemum has 3,000 cultivars, Mudan (Tree peony) over 460, Mei flower over 300, Azalea about 500, Old China rose about 150, Cymbidium goeringii over 100, C. sinense over 130, C. ensifolium over 100, Garden balsam over 50, Shaoyao (Peony) over 200, Chinese lotus over 300, and Camellia (several spp.) over 300. Each flower is divided further into different series, groups (types) and forms, showing clear cultivar diversity. We can use Mei flower, Mudan and the Garden chrysanthemum as examples:

Table 1 Thirty genera of Chinese ornamental species and their percentage of the world species

Genus		Chinese spp.	World spp.	％
1	Maple (Acer)	150	200	75.0
2	Astible (Astilbe)	15	25	60.0
3*	Camellia (Camellia)	195	220	89.0
4*	Wintersweet (Chimonanthus)	6	6	100.0
5	Chloranthus (Chloranthus)	15	15	100.0
6	Corylopsis（Corylopsis）	21	30	70.0
7	Cotoneaster（Cotoneaster）	60	95	63.2
8	Chinese orchid（Cymbidium）	31	50	62.0
9*	Chrysanthemum (Dendranthema)	18	30	60.0
10	Chinese dogwood (Dendrobenthamia)	9	12	75.0
11	Deutzia (Deutzia)	40	60	66.7
12	Keteleeria (Keteleeria)	10	12	75.0
13	Lily (Lilium)	40	80	50.0
14	Lycoris (Lycoris)	15	20	75.0
15	Apple (crabapple, Malus)	24	37	64.9
16	Meconopsis (Meconopsis)	37	45	82.2
17	Michelia (Michelia)	40	60	66.7
18	Lily-turf (Ophiopogon)	33	55	60.0
19	Osmanthus (Osmanthus)	27	40	67.5
20	Parthenocissus (Parthenocissus)	10	15	66.7
21	Paulownia (Paulownia)	9	9	100.0
22	Wood-betony (Pedicularis)	329	600	54.8
23	Phyllostachys (Phyllostachys)	45	50	90.0
24	Primrose (Primula)	294	500	58.8
25	Plum (Cherry, Mei) (Prunus)	140	200	70.0
26	Rhododendron (Rhododendron)	530	900	58.9
27	Spiraea (Spiraea)	65	105	61.9
28	Lilac (Syringa)	26	30	86.7
29	Linden (Tilia)	35	50	70.0
30	Wisteria (Wisteria)	7	10	70.0
	Total of mean	2,276	3,561	63.9

*Some spp. under discussion.

Mei flower (Prunus mume)

Often considered first among Chinese old traditional famous flowers, the Mei flower has over 300 cultivars today. There is a Chinese Mei Flower Research Centre in Wuhan, including the China Mei Flower Cultivar Resources Plantation with over 200 cultivars planted separately according to the system of dividing series, groups (divisions) and forms. The three series are Eumume Series (=P. nume), Apricot Mei Series (=P. mume var. bungo) and Blireiana Series (=P×blireiana=P. cerasifera cv. Pissardii×P. mume).

Wild related species and semi-cultivated types of Mei are also abundant, i. e., with a relatively high degree of genetic diversity. For example, the related species belonging to the subgenus Armeniaca include Prunus armeniaca, P. armeniaca var. holosericea, P. sibirica and P. manshurica, those belonging to the subgenus Prunus include P. salicina, P. simonii and P. ussuriensis, those belonging to the subgenus Cerasus include P. tomentosa, P. japonica, P. humilis and P. glandulosa and those belonging to the subgenus Amygdalus include P. persica, P. davidiana, P. mira, P. triloba, P. kansuensis, P. ferganensis, P. tangutica, P. Tenella and P. amygdalus.

Mudan (Paeonia spp. et cvs.)

There are seven of more woody species of Paeonia in the world, all indigenous to China.

Mudan cultivars are significant in genetic diversity and several Paeonia species have entered into cultivar breeding and evolution, resulting in 5 series (cultivar groups):

a. Suffruticosa Series: Paeonia suffruticosa and its wild variety var. spontanea comprise the main “constituent-origin species”, including more than 400 cultivars totally planted mostly in Central-North China and North-West China.

b. Gansu Series: Mainly P. rockii (=P. papaverace=P. suffruticosa var. papaveracea) and its hybrids and derivatives, with generally high stems, eminent dark-purple petal-bases and strong resistances to various unfavourable environmental conditions. It comprises more than 80 cultivars, with the cultivation centre being Gansu Province.

c. Yangtze Series: Constituent-origin species being mainly P. ostii, mostly adapted and cultivated in the provinces of Anhui, Jiangsu and Zhejiang as well as Shanghai where there is a moist and hot climate.

d. Delavayi Series: mainly P. delavayi, originated in northwestern Yunnan, southwestern Sichuan and southeastern Tibetan Plateau.

e. Lutea Series: mainly P. lutea, originated in middle and northwestern Yunnan, southeastern Sichuan and southeastern Tibetan Plateau and its var. ludlowii originated in southeastern Tibetan Plateau.

Garden chrysanthemum (Dendranthema×grandiflorum)

Garden chrysanthemum, the most popular famous traditional flower of China, is of Chinese origin and stands first among the annual product values of world ornamentals. There are 30 species of the genus Dendranthema in the world, with about 18 species originating in China. It is estimated that the sum total of cultivars in the world is about 20,000~30,000, while China has over 3,000 cultivars of 22 different forms. Considering both the diversity of cultivars and the abundance of relatives as well the cultigen-complex of complicated constituent-origin species, the Garden chrysanthemum is significant in terms of genetic diversity. This is why many specialists in horticulture and botany consider the Garden chrysanthemum and the modern rose as the two modern miracles of flower breeding.

Diversity of origin is the main reason for such genetic diversity. Chinese horticulturists and botanists have studied this problem for nearly half a century. They analyzed ancient history, literature, poems and paintings as well as other relevant reference materials and information, and then a series of interspecific crosses between wild Dendranthema species were made so as to “synthesize” the artificial D. × grandiflorum of today, and to use Random Amplified Polymorphic DNA (RAPD) to fingerprint them. These comprehensive studies support the conclusion that the Garden chrysanthemum originated mainly by artificial selection from variants between natural interspecific hybrids of D. vestitum and D. indicum and then D. zawadskii and some other wild Dendrantema spp. took part in the genesis process later. Thus the cultigen-complex Dendranthema ×grandiflorum emerged finally, appearing for the first time approximately 1,600 years ago in East-Central China.

Wild related Dendranthema spp. of Chinese origin are abundant, making up 60% of the sum total of the world species. They are D. vestitum, D. indicum, D. zawadskii, D. chanetii, D. naktongense, D. nankingense, D. oreastrum, D. potentilloides, D. arosanense, D. maximowiczii, D. glabriusculus, D. dichrum, D. argyrophyllum, D. rhombifolium, D. hypargyrum, D. lavandulifolium and D. mongolicum.

Other ornamental plants

In the genus Rosa, distributed widely in warm and subtropical regions of Asia, Europe, Africa and America, there are some 200 species. China possesses 82 Rosa species, making up 41% of the total world species. The history of rose cultivation in China is long, 40 choice cultivars, all everblooming and double-flowered, being in cultivation during the North Song Dynasty (960~1127 A. D). During the end of the 18th century and the beginning of the 19th century, 4 cultivars of 2 China rose species were introduced into Europe. European breeders, using these as key germplasms in interspecific hybridization with local species successfully produced the first Hybrid Tea Rose (HT) in 1867. The four cultivars introduced into Europe were Rosa chinensis cv. Semperflorens (Slater’s Crimson China Rose), R. chinensis cv. Pallida (Parson’s Pink China Rose), R. × odorata cv. Hume’s Blush Tea-Scented China Rose and R.×odorata cv. Park’s Yellow Tea-Scented China Rose. Their main contribution was to convey such key properties as continuous-blooming and yellow flowers (in some cultivars) to their hybrid progenies, both properties being not found in all European species. Today, modern roses have developed into 6 groups with over 16,000 cultivars, comprising one of the miracles of flower breeding (the other is the Garden chrysanthemum). Hence, the special historical contribution of old China roses was their key germplasm, through interspecific hybridization, giving the various cultivar diversities to modern roses.

Besides those listed in Table 1, other ornamental trees such as Davidia involucrat, Ginkgo biloba, Metasequoia glyptostroboides, Cathaya argyrophylla, Pseudotaxus chienii, Emmenopterys henryi, Tsoongiodendron odorum, Tapiscia sinensis and Roiptelea chiliantha are rare, being mono-specific. Furthermore, there are some species in the following genera, which are rare and unique ornamental trees and shrubs i. e., Magnolia, Phoebe, Ormosia, Liriodendron, Koelreuteria, Cupressus, Pinus, Chamaecyparis, Juniperus, Caryota and Trachycarpus.

Among the shrubs, such genera as Abelia, Buddleja, Berberis, Deutzia, Pyracantha, Hydrangea, Philadelphus, Photinia, Cycas and Chuniophoenix, include many species native to China with extra ornamental qualities. Herbaceous ornamental plants, such as species of the genera Aconitum, Lycoris, Belamcanda, Callistephus, Dianthus, Gentiana, Primula, Meconopsis, Hemerocallis, Saxifraga, Delphinium and Nelumbo nucifera, are either mono-specific plants, have significant specific diversities, of have abundant cultivar diversities and used by Chinese and foreign horticulturists and landscape architects.

2 Threats to and destruction of Chinese ornamental diversity

China is a country with a high genetic diversity in ornamental plants and is also one where ornamental plant resources are suffering threats and destructions quite seriously. For example, ‘Zao Mei’ (early Mei), opening its flowers at the Mid-Autumn Festival (around September) in the open ground, is now a scarce resource and described first in Fan Chengda’s “ Mei Book” (about 1186 A.D), but not later. There are descriptions and photos of ‘Er Du’ Mei (twice blooming Mei) from Lijiang, Yunnan Province, but it is reported that the several potted plants of that cultivar died recently. More fortunate are the cultivars of the Flavescens Form: One of its cultivars ‘Baiye Xiang’ Mei (hundred-petalled light yellow), first described in the “Mei Book”, found in 1985 after being lost for several hundred years. Cultivars like ‘Huangshan Huangxiang’ (Huangshan flavescens) and ‘Yushan Huangxiang’ (Yushan flavescens), were also discovered during an overall investigation of Mei cultivars in the recent 10 years. But cultivars already found and published are not always secure from destruction or loss. For example, cultivars like’ Zizhi Xiao’ (purple twig small), and Qingming Wanfen’ (late beauty) identified in the Chinese Mei Flower Cultivars (1989) have been lost in recent years.

Because modern overseas rose cultivars are more preferred to traditional roses by Chinese people, old China rose cultivars are becoming fewer. During the 1950s, there were at least 200 Chinese traditional rose cultivars in gardens and parks (some 60 cultivars at Yanling, Henan Province) alone. Today, old cultivars are not commonly seen, only less than 100 traditional ones surviving. If not remedied or saved, the motherland of roses is becoming full of modern rose cultivars (from over 95% to nearly 100%) except for a few fine traditional cultivars.

Tree peony and Camellia are not threatened by outside destruction. Famous cultivars like’ Han Mudan’ (cold Mudan), and several Yellow-flowered camellia cultivars. (Camellia japonica) are, however, seriously endangered or lost. Yellow camellia species (C. nitidissima = C. chrysantha), mainly because their leaves are used as Chinese medicinal herbs and because the plants and seeds are bought by oversea nurseries at high prices, e.g., C. nitidissima in Yongning County, C. wumingensis in Wuming County and C. pingguoensis of Pingguo County, have been almost entirely destroyed in their original habitats.

The genetic diversity of herbaceous ornamental plants are even more seriously endangered. For example, in Zhao Xuemin’s book Treatise on Garden Balsam (1790 A.D.), 233 cultivars of Impatiens balsamina were described. Such excellent and scarce cultivars as ‘Kuihuang Qiu’ (sunflower-yellow ball), ‘Daogua Yaofeng’ (upside-down hanging small green phoenix), ‘Xiang Tao’ (fragrant peach) and ‘Yi-zhang Hong’ (10 feet high red-flowered) have all disappeared. It is estimated that now there are only about 50~60 garden balsam cultivars in China. Just after the foundation of the People’s Republic, China possessed some 7,000 Garden chrysanthemum cultivars. Long-time neglect and destruction during movements in the 1960’s, reduced the sum total of cultivars of the Garden chrysanthemum to about 3,000. Furthermore, the orchids should be considered the most seriously endangered in ferms of specific and cultivar diversity among Chinese herbaceous flowers. Destruction has occurred in nearly all their habitats, with Sichuan, Yunnan and Guizhou being the most significant provinces. In places like Guiyang, Guizhou Province, there have been more than 10 tonnes of Chinese orchid plants (mostly wild resources of Cymbidium spp.) on sale in the markets annually and foreign and local companies and merchants have purchased almost all the wild Lady-slippers Paphiopedilum armeniacum and P. malipoense in Wen-shan District, Yunnan Province.

3 Protection and continuous utilization of Chinese ornamental plant diversity

In recent years Chinese central and local governments have adopted some effective measures in protecting the diversity of ornamental plant resources. For example, all species and cultivars of Yellow camellias were prohibited from being exported in the 1980’s by the Ministry of Forestry. This was then revised to several designated species and varieties in the 1990’s. In addition, nature reserves and gene pools in Guanxi have been constructed to protect Yellow camellia genetic resources, and in Luoyang, Henan Province and Wuhan, Hubei Province, China’s Luoyang Tree Peony Gene Pool and China’s Wuhan Mei Flower Cultivar Resources Nursery have been established, respectively.

Continuous utilization is a measure of active and vigorous protection. In order to protect some wild chrysanthemum species, plants such as Denadranthema vestitum and D. zawadskii, are used to make interspecific crosses with the cultivated early chrysanthemums so that a new cultivar group, the so-called Ground-Cover Chrysanthemum, was created and has found wide use in gardening and scenic-spot construction.