Xerochrysum bracteatum

Xerochrysum bracteatum, commonly known as the golden everlasting or strawflower, is a flowering plant in the family Asteraceae native to Australia. Described by Étienne Pierre Ventenat in 1803, it was known as Helichrysum bracteatum for many years before being transferred to a new genus Xerochrysum in 1990. It grows as a woody or herbaceous perennial or annual shrub up to a metre (3 ft) tall with green or grey leafy foliage. Golden yellow or white flower heads are produced from spring to autumn; their distinctive feature is the papery bracts that resemble petals. The species is widespread, growing in a variety of habitats across the country, from rainforest margins to deserts and subalpine areas. The golden everlasting serves as food for various larvae of lepidopterans (butterflies and moths), and adult butterflies, hoverflies, native bees, small beetles, and grasshoppers visit the flower heads. The golden everlasting has proven very adaptable to cultivation. It was propagated and developed in Germany in the 1850s, and annual cultivars in a host of colour forms from white to bronze to purple flowers became available. Many of these are still sold in mixed seed packs. In Australia, many cultivars are perennial shrubs, which have become popular garden plants. Sturdier, long-stemmed forms are used commercially in the cut flower industry. French botanist Étienne Pierre Ventenat described the golden everlasting as Xeranthemum bracteatum in his 1803 work Jardin de Malmaison, a book commissioned by Napoleon's first wife Joséphine de Beauharnais to catalogue rare plants that she had collected and grown at the Château de Malmaison. The Latin species name bracteatum refers to the papery bracts (often mistakenly called petals) of the flower heads. Henry Charles Andrews transferred it to the genus Helichrysum based on the morphology of its receptacle in 1805, and it was known as Helichrysum bracteatum for many years. Leo Henckel von Donnersmarck described it as Helichrysum lucidum in 1806, and Christiaan Hendrik Persoon as Helichrysum chrysanthum in 1807. It was given the name Bracteantha bracteata in 1991, when Arne Anderberg and Laurie Haegi placed the members that are known as strawflowers of the large genus Helichrysum into a new genus Bracteantha, and designated B. bracteata as the type species. However, they were unaware that Russian botanist Nikolai Tzvelev had already placed X. bracteatum in the new, and at the time monotypic, genus Xerochrysum the previous year. This name was derived from the Greek words xeros 'dry', and chrysum 'golden', likely relating to the nature of the distinctive bracts. Confusion existed for a decade, with Bracteantha appearing in literature and the horticultural trade until it was clarified in 2002 that the latter name took precedence. Strawflower is the popular name for X. bracteatum in Europe, while in Australia it is known as an everlasting or paper daisy. An alternate name in 19th-century Europe was immortelle. X. bracteatum itself is very variable and may represent several cryptic species. Alternately, the Tasmanian species Xerochrysum bicolor may be combined with it in future taxonomic revisions. X. bracteatum and its relatives belong to the Gnaphalieae or paper daisies, a large tribe within the daisy family, Asteraceae. However, a 2002 molecular study of the Gnaphalieae has indicated the genus Xerochrysum is probably polyphyletic, as the two species sampled, X. bracteatum and X. viscosum, were not closely related to each other. X. bracteatum has been recorded hybridising with X. viscosum and X. papillosum in cultivation, and possibly also Coronidium elatum and C. boormanii. The plant is an erect perennial, or occasionally annual, herb that is simple or rarely branched at its base. It generally reaches 20 to 80 cm (8 to 31.5 in) in height, but can have a prostrate habit in exposed areas such as coastal cliffs. The green stems are rough and covered with fine hairs, and are robust compared with those of other members of the genus. The leaves are lanceolate, elliptic, or oblanceolate in shape and measure 1.5 to 10 cm (0.59 to 3.94 in) long and from 0.5 to 2 cm (0.20 to 0.79 in) wide. They are also covered with cobwebby hairs. Sitting atop tall stems above the foliage, the flower heads range from 3 to 7 cm (1 to 3 in) in diameter. Occasionally, multiple heads arise from the one stem. Like the flowers of all Asteraceae, they are composed of a central disc which contains a number of tiny individual flowers, known as florets; these sit directly on an enlarged part of the stem known as the receptacle. Around the disc is an involucre of modified leaves, the bracts, which in Xerochrysum, as in most Gnaphalieae, are petal-like, stiff, and papery. Arranged in rows, these bracts curl over and enclose the florets, shielding them before flowering. They create the impression of a shiny and yellow corolla around the disc. The intermediate bracts are sometimes white, while the outer ones are paler and often streaked reddish or brown (a greater variety of colours are found in cultivars). These bracts are papery and dry, or 'scarious', with a low water content, unlike leaves or flower parts of other plants. They are made up of dead cells, which are unusual in that they have a thin primary and a thick secondary cell wall, a feature only found in sclerenchyma, or structural, cells, not cells of flowers or leaves. The individual florets are yellow. Those on the outer regions of the disc are female, while those in the centre are bisexual. Female flowers lack stamens and have only a very short, tube-shaped corolla surrounding a pistil that splits to form two stigmas, while bisexual or hermaphrodite flowers have a longer corolla, and (as in virtually all members of the family) five stamens fused at the anthers, with the pistil emerging from the center. The yellow corolla and pistil are located above an ovary with a single ovule, and surrounded by the pappus, the highly modified calyx of Asteraceae. It comprises a number of bristles radiating around the florets. Yellow in colour, they persist and are thought to aid in the wind dispersal of the 0.3 cm (0.12 in) long fruit. The smooth brown fruit, known as a cypsela, is 2 to 3 mm long with the pappus radiating from one end. In the wild, X. bracteatum can be distinguished from X. bicolor in Tasmania by its broader leaves and cobwebby hairs on the stems, and from X. macranthum in Western Australia by the flower head colour; the latter species has white flower heads whereas those of X. bracteatum are golden yellow. Xerochrysum subundulatum from alpine and subalpine areas of New South Wales, Victoria, and Tasmania is rhizomatous, and has markedly pointed orange bracts. The eastern Australian species X. viscosum may be distinguished by its rough and sticky leaves.