Craspedia

Craspedia
Orange billy button (Craspedia aurantia)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Craspedia G.Forst.
Species
Craspedia alba - White billy button Craspedia paludicola - Swamp billy button Craspedia aurantia - Orange billy button

Craspedia is a genus of daisies commonly known as billy buttons or woollyheads. They are native to Australia and New Zealand where they grow in a variety of habitats from sea level to the alps. The genus is found in every state of Australia except the Northern Territory. In New Zealand, Craspedia is found south from about East Cape in the North Island to Stewart Island. It also occurs on Campbell Island 660 km S of Stewart Island, and the Chatham Islands, 800 km E of East Cape. Craspedia are rosette-forming herbs with secondarily compound capitula (glomerules) that are borne on erect, unbranched scapes. The glomerules or flower-heads are hemispherical to spherical (like pom poms) and are formed of a massive aggregation of tiny flowers (florets). Most species are perennial with one species recorded as annual. Twenty three-species are currently accepted, six from New Zealand and 17 from Australia. Leaves have considerable variation in form, they range in colour from white through to grass green, and are often covered in fine hairs.

Species of Craspedia are found in a wide range of habitats from coastal to alpine and are generally plants of open areas, sometimes ruderal. Observations of some Australian species suggest they re-establish well after fire. In Australia Craspedia are commonly found growing in association with forest habitats, whereas in New Zealand they are generally excluded from closed Nothofagus forests. Craspedia is never seen in New Zealand or Tasmania in the large, widespread and dense populations that are characteristic of mainland Australia, both in forest and on alpine slopes.

Most Australian non-alpine species are found in native grasslands and shrublands associated with Eucalyptus forests. Alpine species are characteristic of short grasslands, herbfields and flush habitats of the subalpine and alpine zones of Kosciuszko and Tasmania. Outside the temperate climate zone the only recorded annual, Craspedia haplorrhiza, is characteristic of semi-desert steppes, acacia and low eucalypt mallee on the Darling and Riverina floodplains. In New Zealand species exploit an extremely wide range of open habitats ranging from coastal sand dunes to wetland areas, alpine herbfield, fellfield, greywacke rock scree, tall tussock grassland and banks at forest margins. The most unusual habitat is perhaps on the steep, fine greywacke rock scress of the eastern South Island of New Zealand.

Craspedia grows in a wide range of soil types (sands, gravels, clays, earths and loams) derived from different geologies across a broad rainfall gradient. It appears to be intolerant only of extremetly infertile and acidic soils. This is illustrated by the absence of Craspedia from parts of western Tasmania, about 17% of Tasmania, which are characterised by pre-Cambrian quartzose rocks, which produce infertile sandy acid soils that are wet and dominated by a heath vegetation known as 'buttongrass moorland'.

There are two centres of diversity in Craspedia, and both are associated with upland areas. One of these is in the Kosciuzko National Park alpine/subalpine area, where seven species are found. The other centre is a larger area in the north-west of the South Island of New Zealand, which contains several species and about 20 distinct and localised entities.

Cultivation

Craspedia can be propagated by division by cutting a rosette from a clump, but generally seed is a more reliable and rapid method. Seeds will germinate in days if lightly sprinkled on seed raising media and not covered. Plants are generally self fertile. The alpine species are quite fussy about water, needing regular water and excellent drainage. All species prefer cool roots, surrounding the plants with rock, gravel or sand is suitable.

Plants will start growing as a single rosette, and each rosette generally produces only 1 flower stalk. A risky, but effective way to force basal shoots is to let the plant dry out until the leaves wilt, then water the plant. New basal shoots will appear in a few weeks. Tip pruning appears to be ineffective, usually resulting in the death of the plant.

See also

A closely related genus is Pycnosorus, also often called billy buttons. One way to distinguish these genera is to note whether the individual flowers are directly attached to the flower base (Pycnosorus) or are attached via little stalks (Craspedia) [1].

External links

• PlantNET genus page
• FloraBase genus page
• Forster's original diagnosis (project Gutenberg source)