Xerochrysum bracteatum

Xerochrysum bracteatum, commonly known as the Golden Everlasting, is a flowering plant in the family Asteraceae, native to Australia. It grows as a woody or herbaceous perennial or annual shrub to a metre high with green or grey leafy foliage and golden yellow or white flowerheads from spring to autumn, the distinctive feature being the papery bracts which resemble petals. Widespread, it grows 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 lepidoptera (butterflies and moths) and adult butterflies visit the flowerheads.

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 many countries. In Australia, many cultivars are perennial shrubs, and have become popular garden plants. Sturdier long-stemmed forms are used commercially in the cut flower industry.

Contents 1 Taxonomy 2 Description 3 Distribution and habitat 4 Ecology 5 Cultivation 5.1 Cultivars 6 References 6.1 Cited texts 7 External links

Taxonomy

The Golden Everlasting was first described in 1803 by French botanist Étienne Pierre Ventenat as Xeranthemum bracteatum.^[3] The species name bracteatum is Latin, and refers to the papery bracts (often mistakenly called petals) of the flowerheads.^[4] Henry Charles Andrews reclassified it as Helichrysum bracteatum,^[5] a name it was known by for many years. Henckel described it as Helichrysum lucidum in 1806, and Persoon as Helichrysum chrysanthum in 1807.^[6] It was given the name Bracteantha bracteata in 1991,^[7] when Anderberg and 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.^[8] However, they were unaware that Russian botanist Nikolai Tzvelev had already placed Xerochrysum bracteatum in a monotypic (at the time) genus Xerochrysum the previous year.^[9] There was confusion for a decade with Bracteantha appearing in literature and horticulture until it was clarified in 2002 that the latter name took precedence.^[8] A 2002 molecular study of the tribe Gnaphalieae has indicated Xerochrysum is probably polyphyletic, as the two species sampled, X. bracteatum and X. viscosum, were quite removed from each other.^[10]

Strawflower is the popular name for Xerochrysum bracteatum in Europe, while in Australia they are known as everlastings or paper daisies.^[4] An alternate name in 19th century Europe was immortelle.^[11] The species itself is very variable and may represent several undescribed species.^[8] Alternately, the Tasmanian species Xerochrysum bicolor may be combined with it in future revisions.^[12]

Xerochrysum bracteatum has been recorded hybridizing with Xerochrysum viscosum and Xerochrysum papillosum in garden situations, and possibly also Coronidium elatum and C. boormanii.^[13]

Description

The plant is an erect perennial, or occasionally annual, herb which is simple or rarely branched at base. It generally grows from 20–80 cm (8–32 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 to those of other members of the genus. The leaves are lanceolate, elliptic or oblanceolate and measure anywhere from 1.5 to 10 cm (0.6–4 in) long and 0.5 to 2 cm (0.2–0.8 in) wide. They are also covered with cobwebby hairs. Sitting atop tall stems above the foliage, the flowerheads range from 3 to 7 cm (1.2-2.8 in) in diameter, and are occasionally multiple.^[12] Like all Asteraceae, they are composed of a central disc which contains a number of tiny individual flowers, known as florets, which 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 prior to flowering.^[14] Creating a shiny and yellow corolla impression, intermediate bracts are sometimes white, while the outer one are paler and often streaked reddish or brown (a greater variety of colors is found in cultivars).^[15]

The individual florets are yellow.^[15] Those on the outer regions of the disc are female, while those in the centre are bisexual. Female flowers lack stamen and have only a very short tube-shaped corolla surrounding a pistil that splits to form two stigmas, while bisexual or hermaphrodite have a longer one, and (as in virtually all members of the family) five stamens fused by 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 is composed of a number of bristles radiating around the florets.^[16] Yellow in colour, they persist and are thought to aid in the wind dispersal of the 0.3 cm long (0.1 in) fruit.^[16]

In the wild, Xerochrysum 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 flowerhead colour; the latter species has white flowerheads whereas X. bracteatum has golden-yellow. Xerochrysum subundulatum from alpine and subalpine areas of New South Wales, Victoria and Tasmania is rhizomatous, and has markedly pointed orange bracts.^[17]

Distribution and habitat

It occurs in all mainland states and territories as well as Tasmania.^[15] Widespread, it is found from north Queensland across to Western Australia, and in all habitats bar densely shaded areas.^[4] It grows as an annual in patches of red sand in Central Australia,^[18] responding rapidly to complete its life cycle to bouts of rainfall.^[19] It is common among granite outcrops in southwest Western Australia.^[11]

Associated species in the Sydney Basin include blackbutt (Eucalyptus pilularis) in open forest, and the shrubs Empodisma minus and Restio australis in swampy areas.^[20]

Ecology

The brightly coloured bracts act as petals to attract insects such as hoverflies, native bees and small beetles which pollinate the florets.^[14] Native bees recorded visiting the flowers include five species halictid bee of the genus Lasioglossum (subgenus Chilalictus)—L. chapmani, L. eremaean, L. helichrysi, L. immaculatum and L. platychilum.^[21] Grasshoppers also visit.^[22] The caterpillars of Tebenna micalis have been recorded on this species, as have those of the Australian Painted Lady (Vanessa kershawi).^[23]

Experimentation at the Waite Institute of University of Adelaide showed that flower production was related to increasing day length, and in general, plants produced the most flowers from December to March. varying planting times or artificially changing light levels might be ways to increase production of flowers outside these months.^[24]

The plant pathogen Bremia lactucae has infected commercial crops in Italy and California. In 2002 on the Ligurian coast, widespread infection of several cultivars, most severely "Florabella Pink" and to a lesser extent ‘Florabella Gold’ and ‘Florabella White’, resulted in leaf blistering and the development of chlorotic lesions on the leaves, and white patches on the undersides, particularly in areas of poor ventilation.^[25] There was an outbreak of downy mildew in a cultivated crop of Xerochrysum bracteatum in San Mateo County California in 2006; the leaves developed large chlorotic lesions.^[26]

Cultivation

Xerochrysum bracteatum was introduced to cultivation in England in the late 18th century, confirmed from 1791.^[27] German horticulturist Herren Ebritsch obtained material of Xerochrysum bracteatum and developed it at his nursery in Arnstadt near Erfurt in Germany. He bred and sold cultivars of many colours from bronze to white to purple, which spread over Europe in the 1850s. The bracts of these early forms tended to remain cupped around the flowerhead rather than flatten out like the native Australian forms.^[4] These were also annual rather than perennial forms. Many were given cultivar names such as 'atrococcineum' (dark scarlet flowerheads), 'atrosanguineum' (dark blood-red flowerheads), 'aureum' (golden yellow flowerheads), 'bicolor' (red-tipped yellow flowerheads), 'compositum' (large multicoloured flowerheads), 'macranthum' (large rose-edged white flowerheads), and 'monstrosum' (flowerheads with many bracts), although today they are generally sold in mixed seed for growing as annuals.^[28] It is thought that some coloured forms of South African Helichrysum were introduced to the breeding program which resulted in the huge array of colours. Xerochrysum bracteatum was one of several species which became popular with European royalty and nobility from the early 19th century, yet were little noticed in Australia until the 1860s, when they became more prominent in Australian gardens.^[27]

Most of the newer cultivars brought into cultivation in Australia in the latter part of the 20th century are perennials.^[29] ‘Dargan Hill Monarch’ was the first of these, and many more have followed.^[28] Profusly flowering, these come in a whole range of colours from white, yellow, orange, bronze, pink and red. Many lose popularity sometime after their release, with a commercial lifespan of around three years.^[30] Queensland-based company Aussie Winners has a range, known as Sundaze, of compact plants ranging from orange to white.^[31] Plants of this series usually have larger leaves.^[32] This range won the Gran premio d'oro at the Euroflora in Geneva in 2001, for the best new plant series in the previous three years. "Florabella Gold" is a member of the Florabella series, and won the award for best new pot plant (vegetative) in the Society of American Florists' competition of 1999. Other ranges include the Nullarbor series, and Queensland Federation daisies, including "Wanetta Sunshine" and "Golden Nuggets".^[30]

Xerochrysum bracteatum is easy to grow both from seeds and from cuttings, although named cultivars will only grow true from cuttings. Plants benefit from pruning of old growth in winter to allow for new growth in spring. Dead-heading flowers promotes the production of more flowers.^[4] Fresh seed germinates in 3 to 20 days and requires no special treatment.^[12] Plants grow best in acid well aerated soils of pH 5.5 to 6.3, with low levels of phosphorus. They are sensitive to iron deficiency, which presents as yellowing (chlorosis) of the youngest leaves while the leaf veins remain green.^[33]

Flowers attract butterflies to the garden.^[34] Dried flowers are long lasting—up to some years—and are used in floral arrangements and the cut flower industry.^[32] More robust longer stemmed forms are used for commercial cut flowers.^[35] The main factor limiting lifespan of dried flowers is the wilting of stems, so flowers are sometimes wired into arrangements. Immersing flowers in glycerol or polyethylene glycol also lengthens lifespan.^[36]

Cultivars

• Xerochrysum ‘Dargan Hill Monarch’ was a natural form collected around 1.6 km (1 mi) inland from Cunninghams Gap in Southern Queensland in May 1961, and registered in February 1977. It is a low perennial shrub 60 to 80 cm (24–32 in) high and 1.5 m (5 ft) across. The foliage is grey and the large flowers are 7–9 cm in diameter and golden yellow in colour.^[37] It grows best in full sun and fair drainage, and will flower more if dead flowers are removed. Cuttings strike readily, as does seed, although seedlings may differ from the parent.^[29]

• Xerochrysum 'Cockatoo' arose as a spontaneous hybrid between 'Dargan Hill Monarch' and a white flowered perennial form of Xerochrysum bracteatum, in the garden of Victorian plantsman Doug McKenzie in Ocean Grove near Geelong in Victoria, who applied to ACRA for registration which was granted in 1980. It is a dense perennial shrub which reaches around a metre (3 ft) high and wide. The oblanceolate leaves measure 6 to 12 cm (2.4–4.8 in) long and are covered with fine hairs which gives them a greyish cast. Fine hairs also cover the stems. The flowerheads have light lemon yellow bracts and orange centres and average 7 cm (2.8 in) in diameter. They are held on long stems around 12–15 cm (5–6 in) above the foliage. Like all forms, it prefers full sun. Although a perennial, it loses vigour after a few years, at which time it is best replaced. The name 'Cockatoo' was chosen as the shape and colour of the ray florets are reminiscent of the wing feathers of the Sulphur-crested Cockatoo.^[38]

• Xerochrysum 'Golden Bowerbird' is a hybrid, bred by a deliberate backcross of 'Cockatoo' to 'Dargan Hill Monarch' by Doug Mackenzie, who applied for registration with ACRA in 1980 (and granted in 1981). It has much larger flowerheads than both parents, yet is a smaller denser-foliaged shrub, which reaches 40 cm (16 in) high by 70 cm (28 in) wide. The foliage is covered in fine grey hair. On stalks around 10 cm (4 in) above the foliage, the flowerheads measure up to 9 cm (3.6 in) in diameter, although larger ones up to 10 cm are occasionally seen. They have around 300 bracts per flowerhead, compared with 80 for 'Dargan Hill Monarch' and 200 in 'Cockatoo', giving them a "doubled" look.^[39] It is reported as producing fewer flowerheads than 'Princess of Wales'.^[40]

• Xerochrysum 'Princess of Wales' is a spontaneous hybrid, arising from a cross between 'Dargan Hill Monarch' and an annual form. Arising in the Australian National Botanic Gardens in Canberra, it was selected by employee Peter Ollerenshaw. Selected in summer 1983, the cultivar was received by ACRA in March 1985.^[41] It was named in honour of a visit by Diana, Princess of Wales to the gardens in November 1985.^[4] With compact foliage, this form reaches 60 cm (24 in) high and wide. Unlike its parent 'Dargan HIll Monarch', its foliage lacks the hair.^[41] It flowers very profusely,^[40] the large flowerheads borne on stalks 5 to 9 cm (2-3.6 in) above the foliage. Unlike other forms, the stems wither and die naturally after flowering, making way for more new growth and flowers.^[41] The flowerheads are golden yellow and measure 6 cm (2.4 in) across.^[4]

• Xerochrysum ‘Diamond Head’ was a natural form collected around from Diamond Head in New South Wales, where it is quite common on bluffs and cliffs. John Wrigley, curator of the Australian National Botanic Gardens at the time, applied to ACRA to have it registered, which it was in February 1977.^[4] Found on an exposed headland in nature, it grows as a low mat-like perennial shrub 8 cm (3 in) high and 60 cm (2 ft) across. The foliage is green and rough and the flowers are 3 cm in diameter and yellow in colour with an orange centre.^[42] It makes an ideal plant for rockeries, and strikes easily from cuttings during the spring growing period.^[43]

• Xerochrysum ‘Hastings Gold’ was a natural form from Hastings Point to the east of Murwillumbah on the New South Wales far north coast. It is perennial herb with green bushy foliage reaching 25 cm high and 70 cm wide. The golden yellow flowerheads measure 5 cm (2 in) across and are held on stalks 20 cm (8 in) above the foliage. It is smaller than the similarly coloured "Dargan Hill Monarch" and larger than ‘Diamond Head’.^[44]

• Xerochrysum ‘Nullarbor Flame’ was a selection introduced into cultivation in 1997 which produces abundant yellow-centred red flowers with a diameter of 4.5 cm (1.8 in). The plant grows to 50–70 cm (20–28 in) tall and 50–80 cm (20–32 in) wide.^[45]

• Xerochrysum ‘Pink Sunrise’ was developed by Goldup Nurseries in Victoria in 1986, of unknown origin, presumably a hybrid. It is a compact perennial which reaches 30 cm (12 in) high and 60 cm (24 in) wide. The flowerheads are pink in bud, before opening as cream with orange centres.^[46]

• Xerochrysum ‘White Monarch’ was a spontaneous garden hybrid which resembles ‘Dargan Hill Monarch’ but with white flowerheads with orange centres which measure up to 8 cm (3.4 in) in diameter.^[47]

• Xerochrysum ‘Lemon Monarch’ resembles 'Cockatoo', but its lemon-coloured flowerheads have fewer bracts.^[40] It has bushy foliage.^[48]

• Xerochrysum ‘Strawburst Yellow’, patented as 'Stabur Yel', is a form with large bright yellow flowerheads averaging around 6.3 cm (2.5 in) in diameter. IThe result of a planned breeding program in Gilroy, California, it was bred by Jason Jandrew of Goldsmith Seeds from a lemon yellow flowered form crossed with a yellow flowered form in 2005. The pollination occurred in May, the resultant seed sown in September, and what was to become the clone chosen in December for its large flower size, colour and compact foliage.^[49]

• Xerochrysum ‘Lemon Princess’ is thought to be a hybrid between X. bracteatum and X. viscosum.^[50]

References

Cited texts

• Australian Daisy Study Group (Barker, Judy; Greig, Joy; Peate, Natalie; Courtney, Bev; Salkin, Esma; Schaumann, Maureen; Armstrong, John; Thomlinson, Gloria. Everlasting Daisies of Australia. Melbourne, Australia: Shannon Books. p. 57. ISBN 0-9587439-6-7. 
• Stewart, Angus (2001). Gardening on the Wild Side. Sydney: ABC Books. ISBN 0-7333-0791-4. 

External links

• ASGAP: Xerochrysum bracteatum