Iris hexagona
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Iridaceae
Genus: Iris
Subgenus: Iris subg. Limniris
Section: Iris sect. Limniris
Series: Iris ser. Hexagonae
Species:
I. hexagona
Binomial name
Iris hexagona
Synonyms[1]
  • Limniris hexagona (Walter) Rodion

Iris hexagona, commonly known as the Dixie iris, is a species in the genus Iris, it is also in the subgenus Limniris and in the series hexagonae. It is a rhizomatous perennial with long bright green leaves, long thin stem and has small groups of flowers in shades of blue, from violet, to bluish purple, to lavender. It flowers in springtime and is native to the southeastern and south-central US states.

Description

Iris hexagona has thick (around 2–2. cm in diameter), greenish, branching rhizomes, that can spread to form large colonies of plants.[2][3][4] The rhizomes are shallow rooted and can spread up to 30 centimetres (12 inches) per plant.[2][4]

Arising from the rhizomes are the basal leaves, which are yellow-green to bright green and sword-shaped.[3][5][6] They can grow up to between 30–100 cm long (12–39 in),[7][8] (or 2 feet),[9] and between 1.2–3 cm (0.47–1.18 in) wide.[10][5] They overlap at the base, similar to a fan,[3][11] but some leaves grow on the flowering stem.[3][10] After the plant has flowered, the leaves wither and die, to re-grow in the autumn (for the next season).[3]

The flowering stem (or stalk) grows up to between 30–90 cm (0.98–2.95 ft)or 12–36 inches).[7][5][12] The stem is usually straight but sometimes slightly zig-zag,[13][14] or flexuous (winding),[15] with 1 -2 branches.[10]

At the top of the stem are several groups of flowers in later spring,[3][11] between late March to May (in the US),[10][5] and between June and July (in the UK).[16] Each flower arises from an axil (or spathe),[3] of a reduced leaf (except the top flower),[9] and the single (or double) flowers open in succession.[2][11][14] They have a slight fragrance which is similar to sandalwood.[2][17]

The flowers come in a range of shades of blue, from violet, to bluish purple, to lavender.[5][8][15] Although there are occasionally white or greenish-white forms.[7][8][12]

The flowers are generally between 4 and 4.75 inches (10.2 and 12.1 centimetres) across.[4][13][5] They have yellow signal, crest, ridge or mid-rib,[4][7][12] and a perianth tube of 2–3 cm,[10] and 3 sepals (or falls) that are widely spreading (about 2 inches or 5 cm) and arching downward.[4][17][11] The 3 standards are smaller and narrower than the sepals.[17][11][9]

It also has linear yellow anthers.[6]

After flowering, the plant produces a seed capsule in early summer.[17] The six-angled seed pod,[11][8] (which gives rise to its name 'hexagona'),[9] has a ventricose (a swelling on one side).[17][6][15] It is between 3–6 cm long (1.2–2.4 in).[17] The large and heavy pods, contain large light brown seeds that are D-shaped and 4–6 mm (0.16–0.24 in) across. The seeds are generally described as being 'corky', so they can float on the water.[3][10]

Biochemistry

As most irises are diploid, having two sets of chromosomes. This can be used to identify hybrids and classification of groupings.[16] It has a chromosome count: 2n=44 (Riley, 1942).[4][18] and 2n=44 (Snoad 1952).[17]

Taxonomy

It has the common name of Dixie iris,[3][4][19] (Dixie is a common name for the southeastern United States.[20]) and it also occasionally known as 'Carolina iris'.[10][21][22] In Florida, it was known as the 'Prairie iris',[20] but this due to a population of Iris hexagona var. savannarum which was later classified as a synonym of Iris savannarum.[23] Most of the I. hexagona population in Florida was re-identified as Iris savannarum.[24]

The name 'hexagona' refers to the six angled seed head.[20]

The Louisiana irises and the name of the series of Hexagonae are derived from Iris hexagona, which was published (in Latin) and described by Walter in 'Flora Caroliniana' page 66 in April–June 1788.[25][26][13]

Iris hexagona is a name accepted by the RHS.[27]

Native

Iris seen in Lakeland, US

Iris hexagona comes from the southeastern and south-central US states along the Atlantic and Gulf coasts, in Alabama, Florida, Georgia, Louisiana, Texas, Tennessee and South Carolina.[4][16][28]

It is found in wetlands and low roadside ditches in Florida and South Carolina,[10] and west of Tennessee River near Johnsonville in Benton County, Tennessee, Hollow Rock and Carroll County, Tennessee. It was found to be one of the rarest irises in Florida and South Carolina.[22]

It was found in Nassau County and Duval County in north-eastern Florida in 1933. But these populations have been extirpated,[14] although the populations in Dixie County and Taylor County are stable.[10] Same as the population in the lowlands near the Santee River in South Carolina.[14]

Habitat

It is ordinarily found in swamps,[5][15] ditches,[14] or marshes and wet prairies.[3][11][29]

Cultivation

The Louisiana irises generally all have similar cultivation requirements. They need 6 hours of full sunlight per day,[18]), moist, acidic soils (pH of 6.5) with a high organic and fertility content.[18][30] They have a high moisture requirement during the growing season to be able to flower prolifically.[3]

The new leaves grow in the autumn and consequently suffer in winter (if heavily frosted).[9]

They can be used planted by the edges of ponds and pools or they can be planted in the water – but need the rhizomes pinned into the ground to stop them floating away.[30] If grown in borders, they need a mulch to retain moisture (in the soil) and to protect the rhizomes from sun burn.[18]

The iris seed is not hard to raise, but does take many years to germinate and then they take 3–5 years before reaching flowering stage.[31] The seed should be sown before they dry out.[18]

Iris brevicaulis and Iris hexagona are primarily pollinated by bumblebees.[32]

Propagation is best carried out by division of the rhizomes, which is best carried out in late summer or autumn when the plants are dormant.[18] The ground must be prepared before planting, with the addition of a generous amount of organic matter and the soils dug to about 6 inches (15 cm) deep (to allow for new root growth). Plants require dividing every 3–4 years to promote good flowering. They can combine with other plants but tend to 'move' to suitable positions. If using a fertilizer (or feed), sprinkle in late January or February, before the plant is in flower.[18][30]

Iris giganticaerulea and Iris hexagona are considered too tender for cultivation in the UK,[33][7] although in Kew Gardens (in London) the plant is grown in a rock garden, near a stream.[5] Botanist William Rickatson Dykes recommends a sheltered position.[9]

It is thought to be hardy to −15 °C (5 °F) in the UK.[5]

In the US, they best grown in the southeastern states.[3] It is listed as a native plant to be suitable use in landscaping in Georgia.[28]

The rhizomes (thickened roots) of Iris hexagona contain poison. If eaten, it could cause nausea, vomiting, abdominal pain, diarrhoea and an elevated temperature. The roots, seeds and plant sap can also cause skin irritation if touched.[11]

Research has also been carried out on the effects of saltwater on the Iris. Normally, saltwater getting into a wetland ecosystem can destroy or damage many native plant populations. Iris hexagona is a salt-sensitive species. The 2-year research found that saltwater affected the iris flowering times by several days, since Iris flowers are only receptive to pollinators for 2 days or less. This could have significant effects on iris colonies. It also means that the iris can be 'stressed' during episodic events (such as tropical storms).[34]

References

  1. ↑ "Iris hexagona Walter is an accepted name". theplantlist.org. 23 March 2013. Retrieved 26 November 2014.
  2. 1 2 3 4 "Iris hexagona". fs.fed.us. Retrieved 28 November 2014.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 Hibbard, Kenneth L. (25 May 2010). "FDACS-P-00124 Volume 49, Number 3, May – June 2010". freshfromflorida.com. Retrieved 28 November 2014.
  4. 1 2 3 4 5 6 7 8 Kramb, D. (21 September 2004). "Iris hexagona". signa.org. Retrieved 28 November 2014.
  5. 1 2 3 4 5 6 7 8 9 Phillips, Roger; Rix, Martyn (1991). Perennials Vol. 1. Pan Books Ltd. p. 188. ISBN 9780330327749.
  6. 1 2 3 Stephen Elliott (1821) A sketch of the botany of South-Carolina and Georgia, p. 46, at Google Books
  7. 1 2 3 4 5 Cassidy, George E.; Linnegar, Sidney (1987). Growing Irises (Revised ed.). Bromley: Christopher Helm. ISBN 978-0-88192-089-5.
  8. 1 2 3 4 Edwin B. Smith Keys to the Flora of Arkansas, p. 327, at Google Books
  9. 1 2 3 4 5 6 Dykes, William (2009). "Handbook of Garden Irises" (PDF). beardlessiris.org (The Group for Beardless Irises). Retrieved 28 November 2014.
  10. 1 2 3 4 5 6 7 8 9 "FNA Vol. 26 Page 374, 391, 392, 393, 394". efloras.org. Retrieved 28 November 2014.
  11. 1 2 3 4 5 6 7 8 "Iris hexagona". plants.ces.ncsu.edu. Retrieved 3 December 2014.
  12. 1 2 3 "Iris summary" (PDF). pacificbulbsociety.org. 14 April 2014. Retrieved 28 November 2014.
  13. 1 2 3 Dillard, Tom W. "FROM NEW ORLEANS TO NEW ZEALAND, History and Development of The Louisiana Irises". zydecoirises.com. Retrieved 28 November 2014.
  14. 1 2 3 4 5 Ward, Daniel B. (August 2011). "KEYS TO THE FLORA OF FLORIDA – 28, IRIS (IRIDACEAE)" (PDF). Phytologia. 2 (93).
  15. 1 2 3 4 John Darby (1841) A manual of botany, p. 241, at Google Books
  16. 1 2 3 Austin, Claire (2005). Irises: A Gardener's Encyclopedia. Timber Press, Incorporated. ISBN 978-0881927306. OL 8176432M.
  17. 1 2 3 4 5 6 7 Barney, Brett (17 April 2014). "(SPEC) Iris hexagona Walter". wiki.irises.org (American Iris Society). Retrieved 3 December 2014.
  18. 1 2 3 4 5 6 7 "Iris hexagona Walter (Dixie Iris)". facstaff.hsc.unt.edu. Retrieved 3 December 2014.
  19. ↑ "Iris hexagona". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Retrieved 3 December 2014.
  20. 1 2 3 Daniel F. Austin Florida Ethnobotany, p. 603, at Google Books
  21. ↑ "Common name: Carolina iris – Scientific name: IRIS HEXAGONA". luirig.altervista.org. Retrieved 3 December 2014.
  22. 1 2 A Fifth Checklist of Tennessee Vascular Plants, p. 73, at Google Books
  23. ↑ "Iris savannarum Small is an accepted name". theplantlist.org. 23 March 2013. Retrieved 26 November 2014.
  24. ↑ "Irises of Florida Newsletter Spring 2003" (PDF). zydecoirises.com (Society of Louisiana Irises). Spring 2003. Retrieved 29 November 2014.
  25. ↑ Iridaceae Iris hexagona Walter. ipni.org (International Plant Names Index). Retrieved 28 November 2014.
  26. ↑ Flora caroliniana : secundum systema vegetabilium perillustris Linnaei digesta; characteres essentia. biodiversitylibrary.org. 1788. Retrieved 28 November 2014.
  27. ↑ "Iris hexagona". rhs.org.uk. Retrieved 4 December 2014.
  28. 1 2 Bonnie Harper-Lore and Maggie Wilson (editors) Roadside Use of Native Plants, p. 156, at Google Books
  29. ↑ Taylor, Sunni J.; Willard, Rees W.; Shaw, Joshua P.; Dobson, Mary C.; Martin, Noland H. (13 May 2011). "Differential response of the homoploid hybrid species Iris nelsonii (Iridaceae) and its progenitors to abiotic habitat conditions". American Journal of Botany. Department of Biology, Texas State University–San Marcos. 98 (8): 1309–1316. doi:10.3732/ajb.1100012. PMID 21821591.
  30. 1 2 3 Neil G. Odenwald and James R. Turner Identification, Selection, and Use of Southern Plants: For Landscape Design, p. 316, at Google Books
  31. ↑ Nick Romanowski Water Garden Plants & Animals: The Complete Guide for All Australia at Google Books
  32. ↑ Taylor, Sunni J.; AuBuchon, Kendall J.; Martin, Noland H. (2012). "Identification of Floral Visitors of Iris nelsonii". Notes of the Southeastern Naturalist. 11 (1). Retrieved 2 December 2014.
  33. ↑ Stebbings, Geoff (1997). The Gardener's Guide to Growing Irises. Newton Abbot: David and Charles. p. 18. ISBN 978-0715305393.
  34. ↑ Van Zandt, Peter A.; Mopper, Susan (November 2002). "Delayed and carry-over effects of salinity on flowering in Iris hexagona (Iridaceae)". American Journal of Botany. Department of Biology, University of Louisiana at Lafayette. 89 (11): 1847–1851. doi:10.3732/ajb.89.11.1847. PMID 21665613. Retrieved 7 November 2014.

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  • Correll, D. S. & M. C. Johnston. 1970. Manual of the vascular plants of Texas.
  • Duncan, W. H. & J. T. Kartesz. 1981. Vascular flora of Georgia: an annotated checklist.
  • Godfrey, R. K. & J. W. Wooten. 1979–1981. Aquatic and wetland plants of southeastern United States, 2 vol.
  • Mathew, B. 1981. The Iris. 107–108.
  • Radford, A. E. et al. 1964. Manual of the vascular flora of the Carolinas.
  • Thomas, R. D. & C. M. Allen. 1993–. Atlas of the vascular flora of Louisiana.
  • Wunderlin, R. P. 1998. Guide to the vascular plants of Florida.
  • Marie Caillet (Editor), 2000, The Louisiana Iris: Taming of a North American Wildflower.

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