The floral emblem for its home state of New South Wales, Telopea speciosissima has featured prominently in art, architecture, and advertising, particularly since Australian federation.

Commercially grown in several countries as a cut flower, it is also cultivated in home gardens, requiring good drainage yet adequate moisture, but is vulnerable to various fungal diseases and pests.

[3] Enveloped in leafy bracts, the flowerheads develop over the winter and begin to swell in early spring,[3][6] before opening to reveal the striking inflorescences.

The exact timing varies across New South Wales, but flowering can begin as early as August in the northern parts of its range, and finish in November in the southern, more elevated areas.

In the first phase, the individual small flowers, known as florets, remain unopened—and the flowerhead retains a compact shape—before they mature and split open, revealing the stigma, style, and anther.

[12] The genus is classified in the subtribe Embothriinae of the Proteaceae, along with the tree waratahs (Alloxylon) from eastern Australia and New Caledonia, and Oreocallis and the Chilean firetree (Embothrium coccineum) from South America.

[13][14] Almost all these species have red terminal flowers, and hence the subtribe's origin and floral appearance must predate the splitting of Gondwana into Australia, Antarctica, and South America over 60 million years ago.

[16] The common name waratah was first applied to this species before being generalised to other members of the genus Telopea and, to a lesser extent, Alloxylon.

[11] The species is found in New South Wales (Australia) from the Watagan Mountains southward to Ulladulla, with a relatively widespread distribution in the Central Coast region.

[4] It usually occurs as an understory shrub in open forest on sandy soils in areas with moderately high rainfall,[3] receiving on average around 1,200 mm (47 in) a year.

The impact of habitat fragmentation and decreased fire interval (time between bushfires) on the gene pool of Telopea speciosissima, which relies on outcrossing, is unclear.

Although largely protected within National Parks and conservation reserves in the Sydney area, most populations are small, numbering under 200 plants, and are often located near urban developments.

[16] Telopea speciosissima is a pyrogenic-flowering species, relying on post-fire flowering followed by production and dispersal of non-dormant seeds to take advantage of favourable growing conditions in the altered environment following a fire.

[19] The species resprouts from a lignotuber, a swollen woody base largely under the soil, that stores energy and nutrients as a resource for rapid growth of new shoots after a bushfire.

[21] The prominent position and striking colour of Telopea speciosissima and many of its relatives within the subtribe Embothriinae both in Australia and South America strongly suggest it is adapted to pollination by birds, and has been for over 60 million years.

[26] Following on from the Parrys were Howard Gay and Arch Dennis, who pioneered growing waratahs at Monbulk in the Dandenong Ranges in the 1940s, Sid Cadwell and Frank Stone, who did likewise in Dural and the Blue Mountains respectively.

[28] Today, New South Wales waratahs are grown commercially in Australia north of Sydney and in the Dandenong Ranges near Melbourne.

Typical symptoms include yellow leaves, wilting, blackening and dieback or part or all of the plant, or lack of proteoid roots.

[32] The most common pathogen is the soil-borne water mold Phytophthora cinnamomi,[33] which appears to be more problematic in cultivated plants than in wild populations.

[32] The larvae of the Macadamia leafminer (Acrocercops chionosema), a moth, burrow along and disfigure the waratah's leaves, and are mainly a problem in lowering the value of cut flower crops.

More problematic is the larger caterpillar of another moth, the Macadamia twig girdler (Xylorycta luteotactella) which can burrow into and disfigure the developing flowerhead.

[48] A tale from the Burragorang Valley tells of a beautiful maiden named Krubi, who wore a red cloak of rock wallaby adorned with the feathers of the gang-gang cockatoo.

[50] The French artist Lucien Henry, who had settled in Sydney in 1879, was a strong proponent of a definitive Australian art style incorporating local flora, particularly the waratah.

The New South Wales waratah was considered alongside the wattle Acacia pycnantha, and debate raged between proponents of the two flowers.

The economist and botanist Richard Baker proposed that the waratah's endemism to the Australian continent made it a better choice than the wattle, as well as the prominence of its flowers.

[58] The species has also been adopted by others, including the New South Wales Waratahs rugby union team since the 1880s,[50] and the former department store Grace Bros in a stylised form for their logo in the 1980s.