Flower profile

Hot rock penstemon

Penstemon deustus

Hot rock penstemon (Penstemon deustus) is a low shrub in the Plantaginaceae family, native in the lower 48 states, blooming mostly May–July across the U.S.

Native to Idaho

Hot rock penstemon is a wildflower that USDA PLANTS lists as native in the lower 48 states.

8states where USDA records it

555ID sightings*

2,217U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: Idaho

Quick look

Penstemon deustus is a species of penstemon known by the common names hotrock penstemon and scabland penstemon. It is native to much of the northwestern United States from the Pacific Northwest to Wyoming, where it grows in many types of forest and open plateau habitat, often on soils heavy in volcanic rock or on limestone outcrops.
From Wikipedia's article Penstemon deustus, CC BY-SA 4.0.

It belongs to the Plantaginaceae family. ^iNaturalist
USDA PLANTS describes it as an herb (forb) / a subshrub with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 8 states. ^{USDA PLANTS}
NatureServe lists it as native to Idaho. ^NatureServe
USDA PLANTS lists its flower color as yellow. ^{USDA PLANTS}
USDA PLANTS gives its bloom period as late spring. ^{USDA PLANTS}
USDA PLANTS lists a mature height of about 2 ft. ^{USDA PLANTS}
iNaturalist has 555 research-grade sightings of it in Idaho, ranking #55 among the 143 flowers on our Idaho list. ^iNaturalist

When does it bloom?

Flowering records by month in Idaho (iNaturalist research-grade observations marked “Flowering”) (30 records)

Conservation status

Federal (U.S. ESA): Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. ^{USFWS ECOS}
NatureServe global: G5 Secure worldwide. ^NatureServe
Idaho: No list Idaho has no state law listing endangered or threatened plants, so we show NatureServe's Idaho ranks instead. NatureServe: SNR, not yet ranked in Idaho.
Rare elsewhere: Other states where NatureServe ranks it rare or missing: UT (S1). (S1 critically imperiled, S2 imperiled, SH possibly extirpated, SX presumed extirpated.)

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsNot well documented

It isn't on the ASPCA plant list.

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records hot rock penstemon in 8 states.

AKMEVTNHWAIDMTNDMNILWIMINYRIMAORNVWYSDIAINOHPANJCTCAUTCONEMOKYWVVAMDDEAZNMKSARTNNCSCDCOKLAMSALGAHITXFL

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

California, Idaho, Montana, Nevada, Oregon, Utah, Washington, Wyoming.

Idaho counties with USDA records: Ada, Adams, Bannock, Bingham, Blaine, Boise, Bonner, Bonneville, Butte, Cassia, Clark, Custer, Elmore, Fremont, Gem, Idaho, Kootenai, Lemhi, Lincoln, Madison, Owyhee, Payette, Shoshone, Twin Falls, Valley, Washington.

Growing conditions

USDA PLANTS gives Hot rock penstemon a high shade tolerance, high drought tolerance and low moisture use. It is rated for soil pH 6.0 to 8.0 and winter lows down to -33 °F.

Shade tolerance: High
Drought tolerance: High
Moisture use: Low
Soil textures it is adapted to: coarse, medium
Soil pH range: 6.0 to 8.0
Minimum temperature tolerated: -33 °F
Frost-free days needed (minimum): 100
Annual precipitation range: 10 to 18 inches
Minimum root depth: 14 inches
Salinity tolerance: Low
Fertility requirement: Low
Growth rate: Moderate
Lifespan: Long
Active growth period: Spring and Summer
Fruit or seed: Brown · Summer to Fall
Can be propagated by: seed
Commercial availability: Contracting Only

From the USDA PLANTS characteristics data for PEDE4. USDA ratings are general guidance for the species, not a guarantee for your garden.

Names, range and relatives

County records: USDA PLANTS lists it in 102 counties across 8 states; the most are in Idaho (26), Oregon (22), California (20).

Other Penstemon on Bloomipedia (16): Foxglove beardtongue, Cobaea beardtongue, Whipple's penstemon, Beardlip penstemon, Palmer's penstemon, Front range beardtongue, Firecracker penstemon, Large-flowered beardtongue, Sidebells penstemon, Royal beardtongue.

More from the Plantaginaceae family (29 on Bloomipedia; most observed first): Bird's-eye speedwell, Butter-and-eggs (common toadflax), Purple foxglove, White turtlehead, Heath speedwell, Canada toadflax, Culver's root, Texas toadflax.

More Idaho flowers

Small-flowered blue-eyed mary

Collinsia parviflora

Native

🌼 Few flowering records in ID

Great mullein

Verbascum thapsus

Introduced

🌼 Few flowering records in ID

Showy milkweed

Asclepias speciosa

Native

🌼 Blooms in ID: June–July

Sources

USDA, NRCS. PLANTS Database, profile PEDE4.
iNaturalist, Penstemon deustus: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Penstemon deustus (lead quoted under CC BY-SA 4.0).
Idaho: Idaho noxious weeds (IDAPA 02.06.09, Section 220).
USFWS, ECOS species database (ESA listing check), October 17, 2026.
NatureServe Explorer, Penstemon deustus (global and state ranks).
Edibility and toxicity: no source found (marked "not well documented").
Photo: Daniel Kennedy via iNaturalist · CC BY 4.0 · resized.