Iris lacustris

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Iris lacustris
Dwarf Lake Iris.jpg

Vulnerable (NatureServe)
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
Order: Asparagales
Family: Iridaceae
Subfamily: Iridoideae
Tribe: Irideae
Genus: Iris
Subgenus: Limniris
Section: Lophiris
Species: I. lacustris
Binomial name
Iris lacustris
  • Evansia lacustris (Nutt.) Klatt
  • Iris cristata var. lacustris (Nutt.) Dykes
  • Iris cristata subsp. lacustris (Nutt.) Iltis
  • Iris lacustris f. albiflora Cruise & Catling [1]

Iris lacustris (also known as dwarf lake iris), is a species in the genus Iris, subgenus Limniris and in the Lophiris section (crested irises). It is a rhizomatous, beardless perennial plant, native to the Great Lakes region of eastern North America. It has lavender blue or violet-blue flowers, a very short stem and long fan-like green leaves. It is cultivated as an ornamental plant in temperate regions. It is closely related to Iris cristata (another North American crested iris).


It is similar in form to Iris cristata but is chromosomally different and smaller.[2][3][4]

It has slender, wiry,[5][6][7] or cord-like,[8] greenish-brown,[9] or yellow rhizomes.[10][11][12] It has a large central section and outer sections, which are 3–5 cm (1–2 in) long and 0.8-1.2 cm wide.[8] The outer sections have fibrous roots (underneath),[8][13] and 2-3 brown scale-like leaves above.[8] It creeps across the ground,[7][13] creating thick clumps of plants.[10][14][15][16]

It has 8-12 sheathing, (fan-like),[7][10][14][15] green or light green,[10][16] basal leaves.[8][16] They are falcate (sickle-shaped) or sword-shaped,[7][14] and linear,[17] and 4–6 cm (2–2 in) long and 10-8mm wide.[3][4][7][8][10][14][17][18] After flowering, the leaves elongate up to 15–16 cm (6–6 in) long and 10mm wide.[8][18][19]

When the plant is not in flower, the leaves of the iris might be confused with false asphodel, (Triantha glutinosa, a white flowered member of the lily family whose leaves are much narrower) which lives in similar habitats. Although, the flower stem of false asphodel is much longer than that of iris and very sticky.[10][15]

It has very short stems,[5][6][10][17][20] which are 0.8–5 cm (0–2 in) long.[4][7][8][14][16][17][20] The stems and flowers are shorter than the leaves.[8][10]

It has green spathes (leaves of the flower bud), which are slightly keeled, and 3–4.5 cm (1–2 in) long.[8][12] They have scarious (membranous) edges.[8]

The short stems have 1 to 2 flowers,[6][8][13][14] in Spring,[4][8][16][19][20] or summer (in Europe),[4] in April,[12] or May,[2][7][8][9][10][11][17][18] or early June,[7][10][11][17] or July.[18] In Spring, it can flower 7 to 10 days earlier then Iris cristata.[16] It can have later flush of flowers in the fall (Autumn),[2][12] or October.[9]

The flowers are 4–6 cm (2–2 in) in diameter,[3][8][14][17][18] come in shades of blue,[5][7][10][15][17] violet-blue,[11][12][13][16][18][18][19][20] sky blue,[2][4][8][13] deep blue,[7][13][14] lavender blue,[19][21][22][23][24] lilac,[6][7][14] or deep purple.[9][15][19] A white form has occasionally, also been found.[2][4][5][7][10][14][16][21][22][23]

It has 2 pairs of petals, 3 large sepals (outer petals), known as the 'falls' and 3 inner, smaller petals (or tepals), known as the 'standards'.[17][20][25] The obovate,[6] falls are 2–2.3 cm (1–1 in) long and 0.8 cm wide.[6][7][8] They taper towards the claw (section closest to the stem). They have a white signal patch, which has a deep violet margin,[13] and 3 central, orange,[9][15] gold,[21][22][23] or yellow and white toothed (or fimbriated - fringed) ridges (or crests).[2][4][6][8][9][12][14] The signal patch guides bumblebees in to the middle of the flower, to pollinate it.[12][13] The standards are narrowly oblanceolate, 1–1.5 cm (0–1 in) long and 0.4-0.5 cm wide.[8] They are shorter and narrower than the falls.[8][9][18]

It has a yellow funnel-like, perianth tube, which is 1–2 cm long.[2][4][8][18] The tube is shorter than Iris cristata.[23] It has a trigonal (or triangular), ovary, which is 0.8–1 cm long.[8] It has a 1–2 cm long style, which has linear crests and wavy (crenate) edges.[8] The style arm guides bumblebees to the lower section of the sepal, to reach the nectar.[13]

After the iris has flowered, between late June to late July,[18] it produces a roundly triangular,[8] or ovoid,[2][7] seed capsule,[17] which are covered by the spathes.[8] The capsules are 1.2 mm long and 8 mm wide.[7][8] Inside the capsule, are 3mm wide, dark brown seeds,[8][18] which have a white appendage (or aril, fleshy thickening of seed coat),[18] spiralled around the seed. This spiral or corkscrew-like appendage is called an eliaosome.[14] The eliaosomes are used as energy-rich food sources by ants,[14] who help pollinate the plant.[12]


In 1994, a study was carried out on the genetic make-up of Iris lacustris.[26]

In 2000, a study was carried out on Iris cristata and Iris lacustris, looking at the genetic variation of both irises.[27]

As most irises are diploid, having two sets of chromosomes, this can be used to identify hybrids and classification of groupings.[25] It has been counted several times, 2n=42, Simonet, 1934; n=21, 2n=42, Chimphamba, 1973 and 2n=32, Pringle, 1976.[28] It is normally published as 2n = 32, 42.[2][8][12][21][23]


Iris lacustris foliage and flowers

It is pronounced as (Iris) EYE-ris (lacustris) lak-US-triss.[19]

It has the common name of dwarf lake iris,[2][7][10][13][15][16][17][18][19][20][23][29][30][31][32] lake iris,[14][28] and Great Lakes iris.[23]

The Latin specific epithet lacustris means "of lakes".[10][20]

The iris was found on Mackinac Island in 1810 by Thomas Nuttall. The botanist travelled from Detroit by canoe with French Canadian voyagers and the surveyor for the Michigan Territory.[10]

It was first then published and described by Thomas Nuttall, in 'The Genera of North American Plants' (published in Philadelphia, USA) Volume1, Issue23 on 14 July 1818.[6][29] [33]

An illustration of the iris was published in Wild flowers of the United States by Rickett, plate 11 in 1966.[4]

It was verified by United States Department of Agriculture and the Agricultural Research Service on 15 April 1994, then updated on 3 December 2004.[29]

It is a close relative to Iris cristata, the only other crested iris native to North America. However, unlike it, Iris lacustris is found only in small areas of the Great Lakes region that have been glacier-free for only 11,000 years.[27] It was once thought to be a form of Iris cristata,[5] (by William Rickatson Dykes in 1913[9] and other authors), later chromosomal studies confirmed the two were separate species.[2][26]

Distribution and habitat[edit]

Iris lacustris is native to temperate regions of northern America.[2][4][12][24][29]


It is found in Canada,[11] within the province of Ontario (on the Bruce Peninsula and Manitoulin Island).[7][10][15][16][29][31]

It is found in U.S.A., within the states of Michigan,[2][7][8][10][11][16][30][31] Wisconsin,[2][7][8][10][16][29][30][31] and, infrequently in Ohio.[2][8][34]

It is found on northern shores and smaller islands of Lake Michigan,[7][15][17][23][31] Lake Huron,[6][7][12][15][23][31] and Lake Superior,[6][9][23] within the Great Lakes region.[2][4][7][10][16]

The majority of iris populations are within 500 m of the shore of Lake Huron, but the largest ones can occur up several kilometres away from the lake.[15]


It grows on the Great Lakes shorelines in cool, moist lake shore air.[13]

It is found on sand,[3][12][13][15][30][31] or in thin soil over limestone-rich gravel,[2][10][15][16][17][23][31] in calcareous (chalky) soil,[16][18][23] or bedrock.[3][7][8][10][30] It also grows on alvar limestone barrens.[15][20] Along shorelines,[23] old beach ridges,[10][18] beside streams,[9] in ditches,[18] on cliffs,[18][23][31] behind open dunes,[7][10][18] or at the edges of coniferous woods (in Canada and Michigan).[2][13][15][17][31]


Iris lacustris is designated a vulnerable threatened species by federal, state and provincial laws throughout its distribution range.[18][23][26][35]

It was added to the U.S. List of Endangered and Threatened Wildlife and Plants on 28 September 1988.[7][30] It is on the U.S. Fish and Wildlife Service's endangered species program.[7]

It was listed by the federal US government as 'threatened', since 1 February 2001.[12][29]

It has become threatened due to habitat destruction, from shoreline development,[7][13] from road-widening projects, chemical spraying and salting, and off-road vehicle use have caused disturbance and destruction of habitat,[7] and degradation of habitats.[10]

Due to being a protected species, plants can not be dug up or seeds gathered.[19] A permit is required for any project (including research, development, and construction) which may "take" or "harm" threatened or endangered species in Michigan.[10]

Also 37% of the Canadian population is on land in protected areas.[15]

Shoreline development has also improved some habitats by opening up the canopy and creating new open ground.[15]


It is hardy to between USDA Zone 4 and Zone 7.[11][16][19][23] and European Zone H2[4] It is hardy in Europe,[12] and in the UK.[6][24]

It is tolerant of a range of soils,[2] but prefers moist, slightly acidic neutral soils.[16]

It flowers mostly in semi-open habitats with partial sun.[7][16][19] Although it can tolerate sunny sites.[11]

It can grow in a peat bank,[24] or can grow in a six-inch pot or container.[6]

It is rarely offered for sale in Europe.[12]

A specimen has been grown in Cambridge Botanic Garden.[6]


Like many other irises, most parts of the plant are poisonous (rhizome and leaves), if mistakenly ingested can cause stomach pains and vomiting. Also handling the plant may cause a skin irritation or an allergic reaction.[19]


In 1998, Iris lacustris was designated the state wildflower of Michigan,[31][36] where the vast majority of populations exist.[37]


  1. ^ "Iris lacustris Nutt. is an accepted name". (The Plant List). 23 March 2013. Retrieved 28 March 2015. 
  2. ^ a b c d e f g h i j k l m n o p q r s British Iris Society (1997) pL6uPLo7l2gC &pg=PA115 A Guide to Species Irises: Their Identification and Cultivation, p. 115, at Google Books
  3. ^ a b c d e "Iris lacustris". Retrieved 9 April 2015. 
  4. ^ a b c d e f g h i j k l m James Cullen, Sabina G. Knees, H. Suzanne Cubey (Editors) The European Garden Flora Flowering Plants: A Manual for the Identification (2011) , p. 257, at Google Books
  5. ^ a b c d e Cassidy, George E.; Linnegar, Sidney (1987). Growing Irises (Revised ed.). Bromley: Christopher Helm. p. 131. ISBN 0-88192-089-4. 
  6. ^ a b c d e f g h i j k l m Richard Lynch The Book of the Iris, p. 93, at Google Books
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac "Dwarf Lake Iris Fact Sheet" (PDF). Retrieved 7 April 2015. 
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af "FNA Vol. 26 Page 373, 378". efloras. Retrieved 9 April 2015. 
  9. ^ a b c d e f g h i j Dykes, William. "Dykes on Iris" (PDF). (The Group for Beardless Irises). Retrieved 21 November 2014. 
  10. ^ a b c d e f g h i j k l m n o p q r s t u v w x y "Dwarf Lake Iris (Iris lacustris)". Retrieved 23 March 2015. 
  11. ^ a b c d e f g h "Cotswold Garden Flowers". Retrieved 23 March 2015. 
  12. ^ a b c d e f g h i j k l m n o "Chapter II iris clump and other (part3)". Retrieved 17 March 2015. 
  13. ^ a b c d e f g h i j k l m n "Iris lacustris: Dwarf Lake Iris". Retrieved 9 April 2015. 
  14. ^ a b c d e f g h i j k l m n "Center for Plant Conservation". Center for Plant Conservation. Retrieved 9 April 2015. 
  15. ^ a b c d e f g h i j k l m n o p q "Cosewic Assessment and Status Report on the Dwarf Lake Iris (Iris lacustris) in Canada, 2010" (PDF). 2010. Retrieved 9 April 2015. 
  16. ^ a b c d e f g h i j k l m n o p q r William Cullina The New England Wild Flower Society Guide to Growing and Propagating Wildflowers of the United States and Canada, p. 129, at Google Books
  17. ^ a b c d e f g h i j k l m n Merel R. Black and Emmet J. Judziewicz Wildflowers of Wisconsin and the Great Lakes Region: A Comprehensive Field Guide , p. 28, at Google Books
  18. ^ a b c d e f g h i j k l m n o p q r s "Dwarf Lake Iris". Retrieved 9 April 2015. 
  19. ^ a b c d e f g h i j k "PlantFiles: Dwarf Lake Iris". Retrieved 9 April 2014. 
  20. ^ a b c d e f g h "Ontario Wildflowers". Ontario Wildflowers. Retrieved 9 April 2015. 
  21. ^ a b c d "Iris summary" (pdf). 14 April 2014. Retrieved 23 November 2014. 
  22. ^ a b c "Crested Irises". 22 July 2012. Retrieved 23 March 2015. 
  23. ^ a b c d e f g h i j k l m n o p Zera, Sean (1 June 2005). "Iris lacustris". (Species Iris Group of North America). Retrieved 9 April 2015. 
  24. ^ a b c d Stebbings, Geoff (1997). The Gardener's Guide to Growing Irises. Newton Abbot: David and Charles. p. 76. ISBN 0715305395. 
  25. ^ a b Austin, Claire (2005). Irises; A Garden Encyclopedia. Timber Press. ISBN 0881927309. 
  26. ^ a b c Simonich, Michael T.; Morgan, Michael D. (1994). "Allozymic uniformity in Iris lacustris (dwarf lake iris) in Wisconsin". Canadian Journal of Botany. 72 (11): 1720–1722. doi:10.1139/b94-212. Retrieved 9 April 2015. 
  27. ^ a b Hannan, Gary L.; Orick, Michael W. (2000). "Isozyme Diversity in Iris cristata and the Threatened Glacial Endemic I. Lacustris (Iridaceae)". American Journal of Botany. 87 (3): 293–301. doi:10.2307/2656625. JSTOR 2656625. PMID 10718990. 
  28. ^ a b Walker, Kenneth (13 February 2015). "(SPEC) Iris lacustris Nutt.". (American Iris Society). Retrieved 23 March 2015. 
  29. ^ a b c d e f g "Taxon: Iris lacustris Nutt.". (Germplasm Resources Information Network). Retrieved 23 March 2015. 
  30. ^ a b c d e f "Plants; Endangered, Threatened, Proposed, and Candidates in the Upper Midwest". Retrieved 7 April 2014. 
  31. ^ a b c d e f g h i j k "Iris lacustris Nutt.". Retrieved 9 April 2015. 
  32. ^ Wayne Grady The Great Lakes: The Natural History of a Changing Region, p. 341, at Google Books
  33. ^ "Iridaceae Iris lacustris Nutt.". (International Plant Names Index). Retrieved 23 March 2015. 
  34. ^ Tom S. Cooperrider, Allison Cusick, John T. Kartesz (Editors) Catalogue of the Vascular Plants of Ohio &pg=PA92 agWRx_4tfLoC , p. 92, at Google Books
  35. ^ "The Nature Conservancy". 2009-02-02. Retrieved 2012-05-14. 
  36. ^ "Michigan State Wildflower". Retrieved 2012-05-14. 
  37. ^ "Michigan Natural Features Inventory" (PDF). Retrieved 2012-05-14. 

Other sources[edit]

  • Center for Plant Conservation. Center for Plant Conservation National Collection of Endangered Plants (on-line resource).
  • FNA Editorial Committee. 1993–. Flora of North America.
  • Gleason, H. A. & A. Cronquist. 1991. Manual of vascular plants of north eastern United States and adjacent Canada, ed. 2.
  • Kartesz, J. T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland.
  • Mathew, B. 1981. The Iris. 74–75.
  • Scoggan, H. J. 1978–1979. The flora of Canada, 4 vol.
  • United States Fish and Wildlife Service. U.S. Fish & Wildlife Service. Species Information: threatened and endangered animals and plants (on-line resource).
  • Voss, E. 1972–. Michigan flora.

External links[edit]

Data related to Iris lacustris at Wikispecies