Annual and perennial herbs, shrubs or rarely trees, erect or twining, sometimes aromatic or with milky sap. Leaves alternate or opposite, often in a basal rosette, entire to variously divided; stipules absent. Flower heads (capitula) solitary, in groups or sometimes in compound heads, each consisting of numerous small flowers (florets), developing from the outside in and surrounded at the base by numerous bracts (the involucre) superficially similar to a calyx. Capitula are of 3 kinds: radiate if the outer florets have the petals fused into a flattened strap of some kind (often called a ligule); diskiform if there are at least 2 distinct types of florets present, neither of which has a ligule; and diskoid if all the florets are similar but none has a ligule. Florets stalkless, sometimes with a scale at the base, unisexual, bisexual or sterile, rarely in unisexual capitula, arranged on an expanded disk (receptacle) at the top of the stalk. In radiate capitula, outer florets are often called ray florets and are usually bisexual or female; inner florets are often called disk florets and are usually bisexual. In diskiform and diskoid capitula, outer florets are usually female and inner florets usually bisexual. Calyx absent or modified into a pappus. Corolla fused at the base into a tube, deeply or shallowly 3-5-lobed at apex and of 2 basic forms, regular and irregular. Regular corollas are usually arranged centrally in the capitulum and may be funnel-shaped (tubular) or narrowly cylindrical (filiform). Irregular corollas are usually around the edge of the capitulum and may be 2-lipped or 1-lipped and often have a ligule. The corolla is sometimes absent. Stamens as many as the lobes of the corolla, alternating with them and attached within the corolla tube; anthers linear and usually joined together, often with apical and basal appendages. Ovary inferior, with 1 chamber and ovule attached at the base. Style with 2 long or short branches in fertile florets, unbranched in sterile florets; stigma may be an area covering the whole inner surface of style branches or be in 2 distinct lines along margins of style branches. In the latter case a sterile terminal appendage is sometimes present on each style branch. Fruit dry, single-seeded and indehiscent (achene or cypsela), often with a persistent pappus; pappus often of long barbed or feathery bristles, sometimes of scales, sometimes reduced to a rough cup or crown or absent.
Perhaps the largest flowering plant family, containing many genera prized in horticulture for their ornamental flowers (including members of the genera Aster, Chrysanthemum, Dahlia, Helichrysum, Senecio, Zinnia, etc). The old family name, Compositae, refers the composite flower heads, which look like a single flower but consist of numerous small flowers clustered together.
Many species spread rapidly by seed and for that reason the family has produced many environmental weeds.
Members of several genera are only occasionally available at nurseries (and are not described in detail here). These include: Abrotanella (as A. forsterioides (Hook.) Benth.) from Tas, a tiny tufted alpine herb used in rockeries; Ajania (as A. pacifica (Nakai) K. Bremer & Humphries), a perennial herb with capitula in congested corymbs and rayless outer florets [Chrysanthemum pacificum Nakai]; Ammobium (as A. calyceroides (Cass.) Anderb.) from E Australia, an erect perennial herb with a basal rosette of leaves, small terminal diskoid capitula and yellow florets [Nablonium calyceroides Cass.]; Anacyclus (as A. pyrethrum (L.) Link var. depressus (Ball) Maire), a low herb with white ray florets with 'Golden Gnome' as a listed cultivar; Bartlettina (as B. sordida (Less.) R.M. King & H. Rob.), grown as a specimen shrub for its attractive new growth and fragrant purplish florets [Eupatorium sordidum Less.]; Bedfordia (as B. arborescens Hochr.), a native shrub or small tree good for cool shady positions outside or in a cool glasshouse; Chrysanthemoides (as C. monilifera (L.) Norl.), a tall shrub with yellow florets and fleshy achenes (a noxious weed that should not be grown); Coleostephus (as C. multicaulis (Desf.) Durieu), an annual herb with yellow ray florets, used in rockeries [Chrysanthemum multicaule Desf.]; Craspedia (as C. glauca (Labill.) Sprengel var. glabrata Hook.), a native rosetted herb used in rockeries (several well-known species formerly in Craspedia have been transferred to the genus Pycnosorus); Cratystylis (as C. conocephala (F. Muell.) S. Moore and C. subspinescens S. Moore), woody dioecious native shrubs with small crowded leaves, useful for dry sunny positions; Dymondia (as D. margaretae Compton) from S Africa, a mat-forming perennial with radiate capitula of yellow florets that is used in rockeries; Edmondia (as E. pinifolia (Lam.) Hilliard) from S Africa, a small-leaved shrub with purple diskiform capitula [Helichrysum humile Less.]; Embergeria (as E. grandifolia (Kirk) Boulos) from New Zealand, a stout succulent perennial herb with yellow (purple- or pink-tinged) florets, all of which are ligulate; Eriophyllum (as E. lanatum Forbes) from Canada and the USA, a tufted perennial herb with yellow ray florets; Ewartia (as E. meredithae (F. Muell.) Beauverd) from Tas, a low, cushion-forming plant suitable for rockeries; Gnaphalium (as G. japonicum Thunb.) from Japan, an erect, woolly annual herb with small capitula in compound heads; Grindelia (as G. robusta Nutt. and G. squarrosa (Pursh) Dunal) from N America, bushy biennial or perennial herbs with radiate (sometimes diskoid) capitula of showy yellow ray florets; Gymnocoronis (as G. spilanthoides (D. Don) DC.) from S America, a glabrous, rhizomatous, semi-aquatic perennial herb with diskoid capitula of white florets (a noxious weed in warmer parts of Australia and not to be grown); Hieracium (as H. villosum Jacq.), Shaggy Hawkweed, from Europe, an erect, hairy rosetted herb with moderately large 'radiate' capitula and pale yellow ligulate florets; Ixiolaena (as I. brevicompta F.Muell.) from E Australia, a bushy annual herb with small narrow leaves and small capitula of yellow tubular florets; Ixodia (as I. achillaeoides R. Br.) from SE Australia, a more or less glabrous shrub with variable leaves, small diskoid capitula of creamish florets, and white spreading inner involucral bracts resembling the ligules of ray florets; Jurinea (as J. mollis (L.) Rchb.) from Europe, a perennial herb with mostly divided leaves and large diskoid capitula of rose-purple florets; Kalimeris (as K. incisa (Fisch.) DC.) from E Asia, a perennial herb with toothed leaves and radiate capitula of purple to white ray florets and yellow disk florets [Aster incisus Fisch., Boltonia incisa (Fisch.) Benth.]; Kleinia (as K. gregorii (S. Moore) C. Jeffrey, K. neriifolia Haw. and K. stapeliiformis (E. Phillips) Stapf) from Africa and the Canary Islands, perennial succulents with diskoid capitula grown mainly for their form and colour rather than their flowers [Senecio gregorii (S. Moore) Jacobsen, S. kleinia (L.) Less. and S. stapeliiformis E. Phillips]; Lagenophora [Lagenifera] (as L. stipitata (Labill.) Druce) from Australia, a rhizomatous rosetted perennial herb with toothed leaves, small capitula and short white to blue or violet ligules; Lasiospermum (as L. bipinnatum (Thunb.) Druce) from S Africa, a perennial herb with divided leaves along the stems, radiate capitula, receptacle bracts and woolly achenes that lack a pappus [L. radiatum Trevir.]; Leontopodium (as L. alpinum Cass.), Alpine Edelweiss, from mountainous areas of Europe and Asia, a white-woolly tufted perennial herb with entire leaves and small diskiform capitula in dense corymbs subtended by prominent leaf-like bracts; Leptinella (as L. filicula (Hook. f.) Hook. f. [Cotula filicula (Hook. f.) Benth.] and L. pusilla Hook. f. [Cotula perpusilla Hook. f.]) from SE Australia and New Zealand respectively, prostrate perennial herbs with divided leaves, small stalked capitula in the leaf axils and compressed achenes that lack a pappus; Leptorhynchos (as L. panaetioides (DC.) Benth., L. squamatus (Labill.) Less., L. tenuifolius F. Muell. and L. tetrachaetus (Schltdl.) J.M. Black), native perennial or annual herbs with simple entire leaves along the stems, small diskiform capitula on long stalks and beaked achenes; Leucogenes (L. grandiceps Beauverd) from New Zealand, a tufted perennial herb with small, dense, silvery entire leaves and small diskiform capitula in dense terminal corymbs subtended by prominent leaf-like bracts; Montanoa (as M. hibiscifolia Benth. and M. bipinnatifida (Kunth) C. Koch) from C America, a large shrub or small tree with deeply lobed leaves, smallish pendulous radiate capitula in compound corymbs and white ray florets; Notobasis (as N. syriaca (L.) Cass.), Syrian Thistle, from the Mediterranean region and Asia, an erect spiny annual herb with large white-veined leaves, terminal diskoid capitula, and purple florets (this species has the potential to become a troublesome weed); Othonna (as O. capensis L.H. Bailey) from S Africa, a low trailing herb with succulent cylindrical leaves, 1-6 small terminal radiate capitula that only open in the sun, and usually yellow florets; Pentzia (as P. suffruticosa (L.) Merxm.), Calomba Daisy, from S Africa, an erect annual herb with greyish much-divided leaves, small diskoid capitula in dense terminal compound corymbs, and yellow florets; Podolepis (as P. jaceoides (Sims) Voss), Showy Podolepis, a perennial native herb with mostly basal leaves, erect scape-like stems, each usually with a single terminal radiate capitulum, and straw-coloured florets; Pseudogynoxys (as P. chenopodioides (Kunth) Cabrera, Mexican Flamevine, Orangeglow Vine, from Colombia, a vigorous climbing shrub with narrow, toothed leaves, fragrant radiate capitula to 5 cm across in terminal or axillary corymbs, and orange florets becoming red with age [Senecio confusus (DC.) Britten]; and Pterocaulon (as P. sphacelatum (Labill.) Benth. & F. Muell.), Applebush, from inland areas of Australia, a tall woolly aromatic herb with the many diskiform capitula grouped in terminal compound heads and pink to purple florets. Sanvitalia (as S. procumbens Lam.) from C America is a procumbent annual with large entire leaves, terminal sessile radiate capitula, yellow to orange ray florets and dark purple disk florets; 'Mandarin Orange' is a dwarf to 10 cm tall with black-centred bright orange flowers; 'Pizzaro's Button' and 'Plena' are also listed. Schoenia (as S. filifolia (Turcz.) Paul G.Wilson) is an erect annual herb from WA with very narrow leaves, terminal diskoid capitula, yellow or white involucral bracts and yellow florets [Helichrysum subulifolium F. Muell.]. Serratula (as S. seoanei Wilk.) from SW Europe is an erect perennial, more or less dioecious herb with toothed to divided leaves, terminal diskoid capitula in clusters and usually purple florets. Sonchus (as S. grandifolius Kirk) from New Zealand is a robust rhizomatous perennial herb with large (to 1m long) divided basal leaves, all florets ligulate, purplish and large ribbed achenes. Tithonia (as T. rotundifolia (Mill.) S.F. Blake), Mexican Sunflower, from C America is a tall annual herb with large, almost round, toothed or lobed leaves, large radiate capitula with prominent receptacle scales enclosing the achenes, and yellow or orange ligules. Vernonia (as V. elaeagnifolia DC. [V. elliptica DC.] and V. mespilifolia Less.) from SE Asia and S Africa respectively are shrubs with simple petiolate leaves, diskoid capitula in panicles, and violet or white florets. Wedelia (as W. trilobata (L.) Hitchc.) from N and C America is a creeping perennial herb with large, broad, apically 3-lobed leaves (sometimes entire or toothed), small solitary radiate capitula, and yellow or orange ray florets. Xanthium (as X. spinosum L.), Bathurst Burr, from S America is a robust herb with rigid, 3-pronged spines at the bases of the entire or lobed leaves, and male and female capitula separate on the same plant, the latter lower down and becoming burr-like in fruit, enclosing the florets and achenes. This is a troublesome weed in parts of Australia.
The family includes a number of commercial vegetables, including members of the genera Cichorium (Chicory), Cynara (Cardoon and Artichoke), Helianthus (Sunflower - seeds, oil and tubers), Lactuca (Lettuce) and Tragopogon (Salsify). Carthamus, among others, is a source of oil and dye; Mutisia and Stokesia sources of timber; Tanacetum the source of the insecticide pyrethrins and other members of the fragrant Anthemidae sources of other repellants and flavourings. Many species are sources of medicinal compounds.
Composite flower heads that look like a single flower but consist of numerous small flowers clustered together.
About 1500 genera of 23 000 species (about 200 genera and 1000 species native to Australia) with the greatest diversity in montane tropical and subtropical areas.
This account follows the classification used in Bremer (1994), and draws heavily upon that work, particularly in the formulation of the generic key and the generic descriptions.
The daisies are a difficult group for identification, as differences between genera and species often depend on characters that can only be seen using a microscope or hand lens; the many double-flowered and unusually coloured cultivars in horticulture further complicate identification. A number of terms have been coined to describe various features of the Asteraceae, and these need to be understood by reading the family description carefully and studying the accompanying line drawings.
Source: (2002). Asteraceae. In: . Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.