Azalea

A cultivar is a kind of cultivated plant that people have selected for desired traits and which retains those traits when propagated. Methods used to propagate cultivars include division, root and stem cuttings, offsets, grafting, tissue culture, or carefully controlled seed production. Most cultivars arise from deliberate human manipulation, but some originate from wild plants that have distinctive characteristics. Cultivar names are chosen according to rules of the International Code of Nomenclature for Cultivated Plants (ICNCP), and not all cultivated plants qualify as cultivars. Horticulturists generally believe the word cultivar was coined as a term meaning "cultivated variety".

Popular ornamental plants like roses, camellias, daffodils, rhododendrons, and azaleas are commonly cultivars produced by breeding and selection or as sports, for floral colour or size, plant form, or other desirable characteristics. Similarly, the world's agricultural food crops are almost exclusively cultivars that have been selected for characters such as improved yield, flavour, and resistance to disease. Since the advent of genetic engineering in the 1970s and the rise of its application in crop breeding in the 1980s, very few wild plants are used as commercial food sources. Trees used in forestry are also special selections grown for their enhanced quality and yield of timber, for example American timber company Weyerhaeuser is the leading grower of genetically modified Douglas-fir trees, one of the most commonly harvested trees.

Asterids are a large clade (monophyletic group) of flowering plants, composed of 17 orders and more than 80,000 species, about a third of the total flowering plant species. The asterids are divided into the unranked clades lamiids (8 orders) and campanulids (7 orders), and the single orders Cornales and Ericales. Well-known asterids include dogwoods and hydrangeas (order Cornales), tea, blueberries, cranberries, kiwifruit, Brazil nuts, argan, sapote, and azaleas (order Ericales), sunflowers, lettuce, common daisy, yacon, carrots, celery, parsley, parsnips, ginseng, ivies, holly, honeysuckle, elder, and valerian (clade campanulids), borage, forget-me-nots, comfrey, coffee, frangipani, gentian, pong-pong, oleander, periwinkle, basil, mint, rosemary, sage, oregano, thyme, lavender, wild dagga, olives, ash, teak, foxgloves, lilac, jasmine, snapdragons, African violets, butterfly bushes, sesame, psyllium, potatoes, eggplants, tomatoes, chilli peppers, tobacco, petunias, morning glory, and sweet potato (clade lamiids).

Most of the taxa belonging to this clade had been referred to as Asteridae in the Cronquist system (1981) and as Sympetalae in earlier systems. The name asterids (not necessarily capitalised) resembles the earlier botanical name but is intended to be the name of a clade rather than a formal ranked name, in the sense of the ICBN.

The Ericaceae (/ˌɛrɪˈkeɪsi.aɪ, -iː/) are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread across 124 genera, making it the 14th most species-rich family of flowering plants. The many well known and economically important members of the Ericaceae include the cranberry, blueberry, huckleberry, rhododendron (including azaleas), and various common heaths and heathers (Erica, Cassiope, Daboecia, and Calluna for example).

Rhododendron section Tsutsusi (spelled Tsutsuji in some older texts) was a subgenus of the genus Rhododendron, commonly referred to as the evergreen azaleas. In 2005 it was reduced to a section of subgenus Azaleastrum. Containing 80 to 117 species, it includes both deciduous and evergreen types and is distributed in Japan, China and northeastern Asia. They are of high cultural importance to the Japanese. Among the species in this genus lie the largest flowering azaleas.

Rhododendron subgenus Pentanthera was a subgenus of the genus Rhododendron. The common name azalea is applied to many of the species, and also to species in some other subgenera. In 2005 it was discontinued and its four sections moved or dismembered.

Japanese gardens (日本庭園, nihon teien) are traditional gardens whose designs are accompanied by Japanese aesthetics and philosophical ideas, avoid artificial ornamentation, and highlight the natural landscape. Plants and worn, aged materials are generally used by Japanese garden designers to suggest a natural landscape, and to express the fragility of existence as well as time's unstoppable advance. Ancient Japanese art inspired past garden designers. Water is an important feature of many gardens, as are rocks and often gravel. Despite there being many attractive Japanese flowering plants, herbaceous flowers generally play much less of a role in Japanese gardens than in the West, though seasonally flowering shrubs and trees are important, all the more dramatic because of the contrast with the usual predominant green. Evergreen plants are "the bones of the garden" in Japan. Though a natural-seeming appearance is the aim, Japanese gardeners often shape their plants, including trees, with great rigour.

Japanese literature on gardening goes back almost a thousand years, and several different styles of garden have developed, some with religious or philosophical implications. A characteristic of Japanese gardens is that they are designed to be seen from specific points. Some of the most significant different traditional styles of Japanese garden are the chisen-shoyū-teien ("lake-spring-boat excursion garden"), which was imported from China during the Heian period (794–1185). These were designed to be seen from small boats on the central lake. No original examples of these survive, but they were replaced by the "paradise garden" associated with Pure Land Buddhism, with a Buddha shrine on an island in the lake. Later large gardens are often in the kaiyū-shiki-teien, or promenade garden style, designed to be seen from a path circulating around the garden, with fixed stopping points for viewing. Specialized styles, often small sections in a larger garden, include the moss garden, the dry garden with gravel and rocks, associated with Zen Buddhism, the roji or teahouse garden, designed to be seen only from a short pathway, and the tsubo-niwa, a very small urban garden.

The flora of Japan comprises a large assemblage of plant species which can be found in Japan, such as sakura, katsura, momiji and azalea. There are many species which are endemic to Japan.