Isopogon trilobus

Isopogon trilobus, commonly known as barrel- or three-lobed cone flower is a shrub that is endemic to south coastal regions of Western Australia. It has distinctive lobed leaves and yellow flowerheads which appear in spring and summer. It is one of the many species described by the botanist Robert Brown

Description

Isopogon trilobus grows as a shrub anywhere from 30 to 2 m (98.4 to 6.6 ft) in height.^[1] The new stems are pale to reddish brown, and initially covered with small fine hairs before becoming smooth. Its leaves are highly variable and have anywhere from three to nine small to deep lobes. The barrel-shaped yellow inflorescences appear from September to January and are terminal (occurring on the ends of stems). Measuring 2.5 to 3 cm (0.98 to 1.18 in) across, they contain many yellow or cream individual flowers.^[2] Flowering is followed by the development of relatively large hairy grey fruit.^[3]

Taxonomy

Botanist Robert Brown described Isopogon trilobus in 1810,^[4] from a collection possibly from Lucky Bay on the southern Western Australian coast. Isopogon tripartitus R.Br., which Brown described in 1830,^[5] is now considered a synonym of the older name.^[6] The species name is derived from the Latin terms tri- "three", and lobus "lobe", and relates to the leaves.^[7]

In 1891, German botanist Otto Kuntze published Revisio generum plantarum, his response to what he perceived as a lack of method in existing nomenclatural practice.^[8] Because Isopogon was based on Isopogon anemonifolius,^[9] and that species had already been placed by Richard Salisbury in the segregate genus Atylus in 1807,^[10] Kuntze revived the latter genus on the grounds of priority, and made the new combination Atylus trilobus for this species, as well as A. tripartitus for I. tripartitus.^[11] However, Kuntze's revisionary program was not accepted by the majority of botanists.^[8] Ultimately, the genus Isopogon was nomenclaturally conserved over Atylus by the International Botanical Congress of 1905.^[12]

Distribution and habitat

The range is from the Stirling Range east to Israelite Bay along the south coast of Western Australia.^[2] It grows on sandplains, dunes or rocky outcrops, on sandy soils, sometimes over laterite, in heathland or shrubland communities.^[1]

Ecology

The colletid bee Hylaeus sanguinipictus and halictid bee Lasioglossum caesium have been recorded visiting the flowerheads of Isopogon trilobus.^[13]

Cultivation

Sensitive to Phytophthora cinnamomi dieback,^[14] Isopogon trilobus requires excellent drainage and full sun. It will likely not tolerate humid climates. Grafting onto eastern species such as I.anethifolius or I.dawsonii could render it more adaptable to a wider climatic range.^[7] Its dense habit and large fruit give it its horticultural potential.^[3]

References