As with food crops, the "discovery, domestication and cultivation" of ornamental plants have a long history. There is indication that lilies were cultivated in China for both medicinal and decorative purposes for over two thousand years. Roses, lilies, violets, anemones, and lavender have been grown as garden plants in Europe since the time of the Roman Empire. At present the diversity of decorative plant species that are cultivated is greater than the diversity of food plants that are commonly grown around the world. In the UK alone an estimated 3,000 species, and a wide range of cultivars and hybrids, are cultivated for ornamental purposes. As "novelty and variety" are important in the horticultural market, plant biodiversity is the key to this industry as it permits the addition of new species or varieties periodically.
Ornamental plants are an important commodity in international trade due to the expanding market. As such, wild species of horticultural value are under threat around the world, due to both habitat destruction and direct exploitation for local and international trade. Important plants of ornamentals trade are: species with bulbs, orchids, cacti and other succulent plants, cycads and insectivorous plants. Over 5,000 species of orchids are recorded in CITES trade statistics during the period 1983-1989. Dendrobium is the most heavily traded genus of orchid exported from Thailand. Sri Lanka also has about 170 species of plants of ornamental value of which 74 are endemic.