Rhododendron in the context of "Washington (state)"

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.

A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple stems and shorter height, less than 6–10 m (20–33 ft) tall. Small shrubs, less than 2 m (6.6 ft) tall are sometimes termed as subshrubs.

Some define a shrub as less than 6 m (20 ft) and a tree as over 6 m tall. Others use 10 m (33 ft) as the cutoff point for classification. Many trees do not reach this mature height because of hostile, less than ideal growing conditions, and resemble shrub-sized plants. Others in such species have the potential to grow taller in ideal conditions. Some only last about five years in good conditions. Others, usually larger and more woody, live beyond 70 years. On average, they die after eight years.

Azaleas (/əˈzeɪliə/ ə-ZAY-lee-ə) are flowering shrubs in the genus Rhododendron, particularly the former sections Tsutsusi (evergreen) and Pentanthera (deciduous). Azaleas bloom in the spring (April and May in the temperate Northern Hemisphere, and October and November in the Southern Hemisphere), their flowers often lasting several weeks. Shade tolerant, they prefer living near or under trees. They are part of the family Ericaceae.

Phytophthora ramorum is the oomycete known to cause the disease sudden oak death (SOD). The disease kills oak and other species of trees and has had devastating effects on the oak populations in California and Oregon, as well as being present in Europe. Symptoms include bleeding cankers on the tree's trunk and dieback of the foliage, in many cases leading to the death of the tree.

P. ramorum also infects a great number of other plant species, significantly woody ornamentals such as Rhododendron, Viburnum, and Pieris, causing foliar symptoms known as ramorum dieback or ramorum blight. Such plants can act as a source of inoculum for new infections, with the pathogen producing spores that can be transmitted by rainsplash and rainwater.

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.

A shrubbery, shrub border or shrub garden is a part of a garden where shrubs, mostly flowering species, are thickly planted. The original shrubberies were mostly sections of large gardens, with one or more paths winding through it, a less-remembered aspect of the English landscape garden with very few original 18th-century examples surviving. As the fashion spread to smaller gardens, linear shrub borders covered up walls and fences, and were typically underplanted with smaller herbaceous flowering plants. By the late 20th century, shrubs, trees and smaller plants tend to be mixed together in the most visible parts of the garden, hopefully blending successfully. At the same time, shrubs, especially very large ones, have become part of the woodland garden, mixed in with trees, both native species and imported ornamental varieties.

The word is first recorded by the OED in a letter of 1748 by Henrietta Knight, Lady Luxborough to the fanatical gardener William Shenstone: "Nature has been so remarkably kind this last Autumn to adorn my Shrubbery with the flowers that usually blow at Whitsuntide". The shrubbery developed to display exciting new imported flowering species, initially mostly from the East Coast of British America, and quickly replaced the older formal "wilderness", with compartments of smaller trees surrounded by hedges, and little colour. It was a further part of the garden, beyond the terrace and flower garden that the house usually opened onto, and when mature provided shade on hot days, some shelter from a wind, and some privacy.

Cannabinoids (/kəˈnæbənɔɪdzˌ ˈkænəbənɔɪdz/) are several structural classes of compounds found primarily in the Cannabis plant or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoactive compound in cannabis. Cannabidiol (CBD) is a major constituent of temperate cannabis plants and a minor constituent in tropical varieties. At least 113 distinct phytocannabinoids have been isolated from cannabis, although only four (THCA, CBDA, CBCA, and their common precursor CBGA) have a confirmed biogenetic origin. Phytocannabinoids are also found in other plants, such as rhododendron, licorice, and liverwort.

Phytocannabinoids are multi-ring phenolic compounds structurally related to THC, while endocannabinoids are fatty acid derivatives. Nonclassical synthetic cannabinoids (cannabimimetics) include aminoalkylindoles, 1,5-diarylpyrazoles, quinolines, and arylsulfonamides, as well as eicosanoids related to endocannabinoids.