Iris thompsonii
Thompson's iris
(c) David Anderson, some rights reserved (CC BY) · licence
Family: Iridaceae · Type: Herb · Native
Conservation status: CNPS 4.3
Iris thompsonii (Thompson's iris) is a native California herb in the Iridaceae family, recognized by forest edge habitat and flower color diagnostic.
Thompson's iris is a native perennial found in northern Coast Ranges and Klamath Ranges in Del Norte County, growing on grassy forest edges and slopes at elevations of 90 to 600 meters. Flowering from April to May, this plant produces pale lavender to violet purple flowers occasionally white to gray, with large sepals 4 to 7 centimeters long and wide. Growing with unbranched stems 10 to 25 centimeters tall arising from slender rhizomes, it develops distinctive basal leaves that are narrow and green at the base. Its leaves are three to four millimeters wide, with one to three cauline leaves transitioning from bract-like at the base to leaf-like near the stem tip. The flower features a funnel-shaped perianth tube 17 to 26 millimeters long, with elegant obovate sepals and petals that create a graceful, delicate appearance.
Identification and appearance
Key characters: 10 sympatric species; forest edge habitat and flower color diagnostic
Habitat and range
Habitat: Common. Grassy slopes in part shade on forest edge
Elevation: 90-600 m
California counties: Del Norte, Siskiyou
Outside California: southwestern Oregon
Bloom period
Iris thompsonii blooms Apr-May.
Conservation status
CNPS 4.3
How to tell it apart
vs Dietes: Iris has broad petal-like style branches; Dietes has thread-like styles and flowers lasting only one day.; vs Canna: Iris has six-parted flowers with drooping sepals; Canna has asymmetric flowers with one petal-like stamen.; vs Hemerocallis: Iris has petal-like style branches opposite stamens; Hemerocallis has simple thread-like styles and six equal tepals.; vs Typha: Iris has showy six-parted flowers; Typha has dense brown cylindrical flower spikes (cattails).; vs Sisyrinchium: Iris has large flowers with drooping outer sepals; Sisyrinchium has small flat flowers with six equal tepals.
Frequently asked questions
Is Iris thompsonii native to California?
Yes. Iris thompsonii is native to California (recorded as native).
When does Iris thompsonii bloom?
Iris thompsonii blooms Apr-May.
Where in California does Iris thompsonii grow?
Iris thompsonii occurs in Del Norte, Siskiyou, at elevations of 90-600 m.
What plant family does Iris thompsonii belong to?
Iris thompsonii is in the Iridaceae family, genus Iris.
Is Iris thompsonii rare or endangered?
Iris thompsonii carries California Rare Plant Rank 4.3, state rank S3.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos · CDFW CNDDB
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.