Iris prismaticaPursh

slender blue iris

WFO wfo-0000783747 Accepted WFO 2026-06 8 photographs CC BY / CC BY-SA

Plate 1 figs. a–h · 8 separate observations

Iris prismatica, photographed by Chase Mathey
fig. a Chase Mathey, CC BY 4.0 / 2021-06-15 / obs. 136604649
Iris prismatica, photographed by Reid Hardin
fig. b Reid Hardin, CC BY 4.0 / obs. 135422016
Iris prismatica, photographed by Reid Hardin
fig. c Reid Hardin, CC BY 4.0 / obs. 134744150
Iris prismatica, photographed by Bonnie Semmling
fig. d Bonnie Semmling, CC BY 4.0 / obs. 133952287
Iris prismatica, photographed by Brian Finzel
fig. e Brian Finzel, CC BY-SA 4.0 / obs. 180622765
Iris prismatica, photographed by Seig
fig. f Seig, CC BY 4.0 / obs. 103193544
Iris prismatica, photographed by Brian Finzel
fig. g Brian Finzel, CC BY-SA 4.0 / obs. 180622644
Iris prismatica, photographed by Matthew Pintar
fig. h Matthew Pintar, CC BY 4.0 / obs. 195951725

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 16 botanical countries

Regions where Iris prismatica is native: Alabama, Connecticut, Delaware, Georgia, Kentucky, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Rhode I., South Carolina, Tennessee, Virginia AlabamaConnecticutGeorgiaKentuckyMaineMarylandMassachusettsNew HampshireNew JerseyNew YorkNorth CarolinaSouth CarolinaTennesseeVirginia DelawareRhode I.
Native distribution of Iris prismatica, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows. Regions too small to draw at this scale are marked with a dot.
RegionTDWG codeContinent
Alabama ALA NORTHERN AMERICA
Connecticut CNT
Delaware DEL
Georgia GEO
Kentucky KTY
Maine MAI
Maryland MRY
Massachusetts MAS
New Hampshire NWH
New Jersey NWJ
New York NWY
North Carolina NCA
Rhode I. RHO
South Carolina SCA
Tennessee TEN
Virginia VRG

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Flowering 34 in flower of 43 examined

Peak flowering in Jun. Each bar is the share of Iris prismatica observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 34 of 43 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 10 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Where it actually grows measured, from 265 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -4.9 °C -1.6 °C 2.0 °C
Warmest month, mean daily high 20.5 °C 29.2 °C 31.6 °C
Annual rainfall 1,079 mm 1,208 mm 1,428 mm
Rainfall in the driest quarter 240 mm 265 mm 290 mm

It is found where winters bring light frost. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 265 research-grade observations of Iris prismatica that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one. Climate from CHELSA V2.1 (Karger et al. 2017); occurrences from 10.15468/dl.cgje2x.

Also published as 7 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Iris boltoniana Schult.
  • Iris gracilis Bigelow
  • Iris prismatica var. austrina Fernald
  • Iris prismatica var. prismatica
  • Iris sibirica var. trigonocarpa (A.Braun & C.D.Bouché) Baker
  • Iris trigonocarpa A.Braun & C.D.Bouché
  • Limniris prismatica (Pursh) Rodion.

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.