Crocosmia (/ -/,;), also known as montbretia (//), is a small genus of flowering plants in the iris family, Iridaceae. It is native to the grasslands of southern and eastern Africa, ranging from South Africa to Sudan. One species is endemic to Madagascar.
They can be evergreen or deciduous perennials that grow from basal underground corms. The alternate leaves are cauline and ensiform (sword shaped). The blades are parallel-veined. The margin is entire. The corms form in vertical chains with the youngest at the top and oldest and largest buried most deeply in the soil. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow. The chains of corms are fragile and easily separated, a quality that has enabled some species to become invasive and difficult to control in the garden.
They have colourful inflorescences of 4 to 20 vivid red and orange subopposite flowers on a divaricately (horizontally) branched stem. The terminal inflorescence can have the form of a cyme or a raceme. These flower from early summer well into fall. The flowers are sessile on a flexuose arched spike. The fertile flowers are hermaphroditic. All stamens have an equal length. The style branches are apically forked. They are pollinated by insects, birds (sunbirds) or by the wind. The dehiscent capsules are shorter than they are wide.
The genus name is derived from the Greek words krokos, meaning "saffron", and osme, meaning "odor" – from the dried leaves emitting a strong smell like that of saffron (a spice derived from Crocus – another genus belonging to the Iridaceae) – when immersed in hot water.
The alternative name montbretia is still widely used, especially for the garden hybrid C. × crocosmiiflora. "Montbretia" commonly used in the British Isles for orange-flowered C. × crocosmiiflora cultivars that have naturalised, while "crocosmia" is reserved for less aggressive red-flowered cultivars. Montebretia is a heterotypic synonym of the genus Tritonia in which some species of Crocosmia were once included. It was named by Alire Raffeneau Delile for Ernest Coquebert de Montbret, a fellow French botanist on Napoleon's Egyptian Campaign.
Species accepted by World Checklist of Selected Plant Families
- Crocosmia ambongensis (H.Perrier) Goldblatt & J. C. Manning – Madagascar
- Crocosmia aurea (Pappe ex Hook.) Planch. (Falling Stars) – eastern + southern Africa from Cape Province to Sudan; naturalised in Azores
- Crocosmia × crocosmiiflora (Lemoine) N.E.Br. - South Africa; naturalised in parts of Europe, Rwanda, Zaire, Assam, Norfolk Island in Australia, Fiji, the Caribbean, Argentina, Tristan da Cunha (C. aurea × C. pottsii)
- Crocosmia fucata (Lindl.) M.P.de Vos – Kamiesberg Mountains in Cape Province of South Africa
- Crocosmia masoniorum (L.Bolus) N.E.Br. (Giant montbretia) – Cape Province, KwaZulu-Natal
- Crocosmia mathewsiana (L.Bolus) Goldblatt ex M.P.de Vos – Drakensberg Mountains in Mpumalanga
- Crocosmia paniculata (Klatt) Goldblatt (Aunt Eliza) – Lesotho, Eswatini, South Africa
- Crocosmia pearsei Oberm. – Lesotho, Free State, Drakensberg Mountains in Mpumalanga
- Crocosmia pottsii (Baker) N.E.Br. (Pott's montbretia) – Cape Province, KwaZulu-Natal
Crocosmias are grown worldwide, and more than 400 cultivars have been produced. Some hybrids have become invasive, especially C. × crocosmiiflora hybrids, which are invasive in the UK, Ireland, Australia, New Zealand,  North Carolina, and the West Coast of the United States.
Other cultivars include:
- Crocosmia curtonus 'Lucifer', scarlet
Crocosmia × crocosmiiflora corms in winter
Close-up of Crocosmia 'Lucifer' in bloom
Montbretia, south Manchester, England
- Kew World Checklist of Selected Plant Families
- "Crocosmia". Dictionary.com Unabridged (Online). n.d. Retrieved 2016-01-23.
- "Crocosmia". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 2020-03-22.
- RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 978-1405332965.
- "Montbretia". Dictionary.com Unabridged (Online). n.d. Retrieved 2023-02-10.
- Manning, John; Goldblatt, Peter (2008). The Iris Family: Natural History & Classification. Portland, Oregon: Timber Press. pp. 144–47. ISBN 978-0-88192-897-6.
- "How to Grow Crocosmias." BBC Gardeners' World Magazine. 20 April 2020. Accessed at GardenersWorld.com on 10 February 2023. "Crocosmias are also known as montbretia, although this tends to refer to the common species Crocosmia x crocosmiiflora."
- Diana Wells. 100 Flowers and How They Got Their Names. Algonquin Books, 1997. pp. 142-143. ISBN 9781565121386
- Missouri Botanical Gardens
- Montbretia Plantlife
- Wildly beautiful but caution should be taken with invasive plants Irish Examiner, 5 August 2017
- Weeds of Australia Queensland Government, 2016
- Common Weeds of New Zealand: Introduced and Invasive Species
- Crocosmia x crocosmiiflora (montbretia) CABI
- Weeds of New Zealand 2016
- Crocosmia x crocosmiiflora North Carolina State University
- Crocosmia x crocosmiiflora University of Georgia
- Crocosmia x crocosmiiflora California Invasive Plant Council
- "Crocosmia 'Hellfire'". RHS. Retrieved 5 May 2020.
- "RHS Plant Selector - Crocosmia 'Lucifer'". Retrieved 15 April 2020.
- "RHS Plant Selector - Crocosmia masoniorum". Retrieved 15 April 2020.
- "Crocosmia 'Paul's Best Yellow'". RHS. Retrieved 5 May 2020.
- "RHS Plant Selector - Crocosmia 'Severn Sunrise'". Retrieved 15 April 2020.
- "Crocosmia × crocosmiiflora 'Babylon'". RHS. Retrieved 5 May 2020.
- "RHS Plant Selector - Crocosmia × crocosmiiflora 'Star of the East' '". RHS. Retrieved 5 May 2020.