Flower profile

Thyme-leaved bluet

Houstonia serpyllifolia

Thyme-leaved bluet (Houstonia serpyllifolia) is a flowering plant in the Rubiaceae family, native in the lower 48 states, blooming mostly April–June across the U.S.

Native to North Carolina

Thyme-leaved bluet is a wildflower that USDA PLANTS lists as native in the lower 48 states. In North Carolina it's most often seen in bloom in April–June.

9states where USDA records it

2,006NC sightings*

2,793U.S. sightings*

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

On our lists for: North Carolina

Quick look

Houstonia serpyllifolia, commonly called thymeleaf bluet, creeping bluet, mountain bluet, Appalachian bluet or Michaux's bluets is a species of plant in the coffee family (Rubiaceae). It is native to the eastern United States, where it is found in the central and southern Appalachian Mountains.
From Wikipedia's article Houstonia serpyllifolia, CC BY-SA 4.0.

It belongs to the Rubiaceae family. ^iNaturalist
USDA PLANTS describes it as an herb (forb) with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 9 states. ^{USDA PLANTS}
NatureServe lists it as native to North Carolina. ^NatureServe
In North Carolina, most iNaturalist sightings of it in flower come in April–June. ^iNaturalist
iNaturalist has 2,006 research-grade sightings of it in North Carolina, ranking #90 among the 192 flowers on our North Carolina list. ^iNaturalist

When does it bloom?

In North Carolina, most flowering sightings come in April–June.

Flowering records by month in North Carolina (iNaturalist research-grade observations marked “Flowering”) (518 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: G4 Apparently secure worldwide. ^NatureServe
North Carolina: Not listed Not on North Carolina Protected Plant Species List (02 NCAC 48F .0301). NatureServe: S3, vulnerable in North Carolina. ^{02 NCAC 48F .0301}
Rare elsewhere: Other states where NatureServe ranks it rare or missing: KY (S1), PA (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.

Please leave it where it grows

Please don't pick or dig this flower: NatureServe ranks it S3 in North Carolina. ^NatureServe

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 thyme-leaved bluet in 9 states.

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recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Georgia, Kentucky, Maryland, North Carolina, Pennsylvania, South Carolina, Tennessee, Virginia, West Virginia.

North Carolina counties with USDA records: Alleghany, Avery, Buncombe, Burke, Caldwell, Cherokee, Clay, Haywood, Henderson, Jackson, Macon, McDowell, Mitchell, Rowan, Swain, Transylvania, Watauga, Yancey.

Names, range and relatives

Other scientific names (synonyms in USDA PLANTS): Hedyotis michauxii.

County records: USDA PLANTS lists it in 45 counties across 8 states; the most are in North Carolina (18), West Virginia (9), Tennessee (7).

Other Houstonia on Bloomipedia (4): Azure bluet, Tiny bluet, Summer bluet, Roundleaf bluet.

More from the Rubiaceae family (18 on Bloomipedia; most observed first): Partridgeberry, Buttonbush, Field madder, Largeflower Mexican clover, Buttonweed, Shiny-leaved wild coffee, Diamond-flowers, Shrubby false buttonweed.

More North Carolina flowers

Partridgeberry

Mitchella repens

Native

🌼 Blooms in NC: April–June

Azure bluet

Houstonia caerulea

Native

🌼 Blooms in NC: March–April

Summer bluet

Houstonia purpurea

Native

🌼 Blooms in NC: May–June

Sources

USDA, NRCS. PLANTS Database, profile HOSE2.
iNaturalist, Houstonia serpyllifolia: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Houstonia serpyllifolia (lead quoted under CC BY-SA 4.0).
North Carolina: North Carolina Protected Plant Species List (02 NCAC 48F .0301).
North Carolina: North Carolina Noxious Weed List (02 NCAC 48A .1702) (the list names any non-native Lythrum; we apply it to purple loosestrife (Lythrum salicaria), which isn't native).
USFWS, ECOS species database (ESA listing check), October 17, 2026.
NatureServe Explorer, Houstonia serpyllifolia (global and state ranks).
Edibility and toxicity: no source found (marked "not well documented").
Photo: Michael J. Papay via iNaturalist · CC BY 4.0 · resized.