Caladenia flava, commonly known as cowslip orchid, is a species of orchid endemic to the south-west of Western Australia. It is a relatively common orchid with a single, hairy leaf and up to three yellow flowers which often have red markings. In 2001 three subspecies were named and a fourth is recognised but not as yet formally described.
Caladenia flava is a perennial herb, which grows from underground stems. The leaf and flowerstalk appear from these to present several yellow flowers during July – December. The leaf is long for the species size, becoming narrower beyond the middle. Flowers are on a long stalk and are between two and five, usually yellow, occasionally pinkish or white, and speckled with magenta. Sepals and petals are broad though long, tapering to a point, and contracted at the base. Lateral sepals may be over 2–3 mm long, the upper sepal is smaller, with a reddish line of splotches along the centre. The flower has a lip over 5 mm with a small claw-shaped structure, three lobes are nearly separate, lateral lobes are ovate, the middle lobe longer and slightly broad, bordered on each side by several long structures (calli). These calli are in two rows, almost a semicircle. A column structure is present, and is winged from the base.
Taxonomy and naming
Caladenia flava was first formally in 1810 by Robert Brown. The description was published in Brown's book Prodromus Florae Novae Hollandiae et Insulae Van Diemen from a specimen in Archibald Menzies' early collection.
- Caladenia flava R.Br. subsp. flava which is the most common and widespread of the four subspecies and has golden-yellow, creamy-yellow or white flowers which are often marked with red and four to six teeth on the labellum;
- Caladenia flava subsp. maculata Hopper & A.P.Br.  which has lemon-yellow flowers with brownish of red blotches and eight to sixteen teeth on the labellum, occurring mostly north of Geraldton and commonly known as the Kalbarri cowslip orchid;
- Caladenia flava subsp. sylvestris Hopper & A.P.Br.  which has pale yellow and cream-coloured flowers which are white near the tips of the sepals and petals, red and four to six teeth on the labellum, occurring between Bunbury and Albany and is commonly known as the karri cowslip orchid.
A fourth subspecies known as 'late red' is recognised but has yet to be formally described. It is a rare subspecies with an unusually large leaf and prominent red markings on the all the sepals and petals, occurring between Beverley and Williams and commonly known as the Brookton Highway cowslip orchid.
Many soil types, laterite, and granite. Common. The species has been identified as occurring with burnt trees, namely marri gum. It often occurs in winter wet areas, in forest, the coastal woodlands, and on the granite outcrops throughout the Southwest Botanical Province. The occurrence is all the regions there, it has also been identified in sandplains, the arid areas, and extending its range to the Coolgardie region.
- Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 25. ISBN 1877069124.
- Brown, Andrew; Dixon, Kingsley; French, Christopher; Brockman, Garry (2013). Field guide to the orchids of Western Australia : the definitive guide to the native orchids of Western Australia. Simon Nevill Publications. pp. 152–153. ISBN 9780980348149.
- Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia. (3rd ed.). Gooseberry Hill: Noel Hoffman. pp. 177–180. ISBN 9780646562322.
- "Caladenia flava". APNI. Retrieved 3 February 2017.
- Brown, Robert (1810). Prodromus Florae Novae Hollandiae. London. p. 324. Retrieved 4 February 2017.
- Hopper, Stephen; Brown, Andrew Phillip (2001). "Contributions to Western Australian orchidology: 2. New taxa and circumscriptions in Caladenia". Nuytsia. 14 (1/2): 175–178.
- "Caladenia flava subsp. flava". APNI. Retrieved 4 February 2017.
- "Caladenia flava subsp. maculata". APNI. Retrieved 4 February 2017.
- "Caladenia flava subsp. sylvestris". APNI. Retrieved 4 February 2017.
- "Caladenia flava subsp. 'late red'". APNI. Retrieved 4 February 2017.
- Pelloe, Emily H. (1930). West Australia Orchids. [Illustrations by the author]. Perth, Western Australia. pp. Page 54.
Usually found around burnt trees, particularly marri gum.
- "Caladenia flava R.Br.". FloraBase. Western Australian Government Department of Parks and Wildlife.