Olearia

Olearia, most commonly known as daisy-bush,[2] is a genus of flowering plants belonging to the family Asteraceae, the largest of the flowering plant families in the world. Olearia are found in Australia, New Guinea and New Zealand. The genus includes herbaceous plants, shrubs and small trees. The latter are unusual among the Asteraceae and are called tree daisies in New Zealand. All bear the familiar daisy-like composite flowerheads in white, pink, mauve or purple.

Olearia
Olearia stuartii
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Tribe: Astereae
Genus: Olearia
Moench[1]
Type species
Olearia tomentosa
Species

See text.

Description

Plants in the genus Olearia are shrubs of varying sizes, characterised by a composite flower head arrangement with single-row ray florets enclosed by small overlapping bracts arranged in rows. The flower petals are more or less equal in length. The centre of the bi-sexual floret is disc shaped and may be white, yellowish or purplish, generally with 5 lobes. Flower heads may be single or clusters in leaf axils or at the apex of branchlets. Leaves may be smooth, glandular or with a sticky secretion. The leaves may grow opposite, alternate, arranged sparsely or clustered. Leaf margins either entire or lobed, with or without a stalk. The fruit are dry slightly compressed, one-seeded, narrow-elliptic or egg-shaped with longitudinal ridges and smooth or with sparse hairs.[3][4][5]

Taxonomy and naming

The genus is named after Johann Gottfried Olearius, a 17th-century German scholar and author of Specimen Florae Hallensis.[6] Originally a large genus, a molecular study has found it to be polyphyletic.[7] Olearia species are used as food plants by the larvae of some Lepidoptera species including Aenetus ligniveren, which burrows into the trunk.

Distribution

There are approximately 180 species of Olearia, of which about 112 species are endemic to Australia. Olearia are found in all states of Australia.[5]

Species
Olearia argophylla
Olearia insignis
Olearia lyallii

The following is a list of Olearia species accepted by the Australian Plant Census or the New Zealand Plant Conservation Network or listed in the Census of Vascular Plants of Papua New Guinea as at April 2019:[8][9][10]

Use in horticulture

Several species are cultivated as ornamental garden plants, and there are hybrids of uncertain or mixed parentage. Among these, the following have been given the Royal Horticultural Society’s Award of Garden Merit:-[11]

  • Olearia macrodonta, New Zealand holly[12]
  • Olearia × mollis ‘Zennorensis’, daisy bush ‘Zennorensis’[13]
  • Olearia × scilloniensis[14]
  • Olearia × scilloniensis ‘Master Michael’[15]

They are generally hardy down to −10 °C (14 °F), but require a sheltered spot in full sun.

References
  1. "Olearia Moench". Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government.
  2. "Olearia". Integrated Botanical Information System (IBIS). Australian National Botanic Gardens. Retrieved 3 May 2019.
  3. "Olearia". VICFLORA online. Royal Botanic Gardens Victoria. Retrieved 5 May 2019.
  4. Holliday, Ivan. "Olearia". Australian Native Plant Society Australia. Retrieved 9 May 2019.
  5. Lander, N.S. "Olearia". PLANTNET. New South Wales Flora Online. Retrieved 9 May 2019.
  6. Moench, Conrad. 1802. Supplementum ad Methodum Plantas. pp. 254-255
  7. Cross, E.W.; Quinn, C.J.; Wagstaff, S.J. (2002). "Molecular evidence for the polyphyly of Olearia (Astereae: Asteraceae)". Plant Systematics and Evolution. 235 (1–4): 99–120. doi:10.1007/s00606-002-0198-9. JSTOR 23645039.
  8. "Olearia". Australian Plant Census. Retrieved 3 May 2019.
  9. "Olearia". New Zealand Plant Conservation Network. Retrieved 3 May 2019.
  10. Conn, Barry J. "Census of the Vascular Plants of Papua New Guinea". Royal Botanic Garden Sydney. Retrieved 4 May 2019.
  11. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 69. Retrieved 14 April 2018.
  12. "RHS Plantfinder - Olearia macrodonta". Retrieved 14 April 2018.
  13. "RHS Plantfinder - Olearia × mollis 'Zennorensis'". Retrieved 14 April 2018.
  14. "Olearia × scilloniensis". RHS. Retrieved 18 January 2021.
  15. "RHS Plantfinder - Olearia × scilloniensis 'Master Michael'". Retrieved 14 April 2018.
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