Penstemon filiformis
Thread-leaved beardtongue
(c) Steve Matson, some rights reserved (CC BY), uploaded by Steve Matson · licence
Family: Plantaginaceae · Type: Subshrub · Native
Conservation status: CNPS 4.2
Penstemon filiformis (Thread-leaved beardtongue) is a native California subshrub in the Plantaginaceae family, recognized by thread-like inrolled leaves highly distinctive.
Thread-leaved beardtongue is a California native perennial ranked 4.2 by CNPS, found in the northern Trinity and northwestern Shasta counties of the Klamath Ranges in open, rocky places and yellow-pine forest at elevations of 400 to 1,700 meters. Flowering from May to July, this plant produces distinctive blue flowers 13 to 16 millimeters long with glandular exteriors. Growing with woody-branched stems 20 to 50 centimeters tall and covered in fine downward-pointing hairs, it develops an intricate growth habit. Its leaves are remarkably thread-like, with tight basal clusters and cauline leaves approximately 0.5 millimeters wide, tightly inrolled and entire. The plant's delicate blue flowers and extremely narrow leaves make it a unique component of its rocky woodland habitat.
Identification and appearance
Key characters: 25 sympatric species; thread-like inrolled leaves highly distinctive
Habitat and range
Habitat: Open, rocky places among shrubs, yellow-pine forest
Elevation: 400-1700 m
California counties: Shasta, Trinity, Siskiyou
Bloom period
Penstemon filiformis blooms May-Jul.
Conservation status
CNPS 4.2
How to tell it apart
vs Epilobium: Penstemon has tubular two-lipped flowers with five stamens; Epilobium has four-petaled open flowers with eight stamens.; vs Keckiella: Penstemon is herbaceous and dies back; Keckiella has persistent woody stems year-round.; vs Salvia: Penstemon has five stamens (one sterile); Salvia has only two fertile stamens and square stems.; vs Ipomopsis: Penstemon has two-lipped tubular flowers; Ipomopsis has star-shaped flowers with five equal lobes.; vs Antirrhinum: Penstemon has a sterile stamen visible inside; Antirrhinum has only four stamens, none sterile.
Frequently asked questions
Is Penstemon filiformis native to California?
Yes. Penstemon filiformis is native to California (recorded as native).
When does Penstemon filiformis bloom?
Penstemon filiformis blooms May-Jul.
Where in California does Penstemon filiformis grow?
Penstemon filiformis occurs in Shasta, Trinity, Siskiyou, at elevations of 400-1700 m.
What plant family does Penstemon filiformis belong to?
Penstemon filiformis is in the Plantaginaceae family, genus Penstemon.
Is Penstemon filiformis rare or endangered?
Penstemon filiformis carries California Rare Plant Rank 4.2, state rank S4.
Related species
Other California species in the same genus, family, or bioregion.
- Penstemon floridus — Panamint beardtongue
- Penstemon floridus var. austinii — Austin's beardtongue
- Penstemon floridus var. floridus — Panamint beardtongue
- Penstemon fruticiformis — Death valley beardtongue
- Penstemon fruticiformis var. amargosae — Amargosa beardtongue
- Penstemon fruticiformis var. fruticiformis — Desert beardtongue
Sources: Jepson eFlora · CNPS Rare Plant Inventory · 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.