Plant Profile

Labrador-tea

Compiled by the Omnia Sana editorial team from the plant database ·Last updated August 15, 2026

Rhododendron tomentosum

Family: Ericaceae · Parts used: Leaf, Stem · Also known as: Labrador tea, bog tea, Hudson's Bay tea, marsh tea

The complete database record: 3 documented constituents, 3 pharmacological actions, 7 traditional / indicated uses, with 17 cited sources.

Botanical Description

Low evergreen shrub (Ericaceae), 30-100 cm tall. Leaves are narrow, leathery, with in-rolled margins and a dense, rust-coloured, woolly felt on the underside, strongly aromatic when crushed. Small white flowers are borne in terminal clusters.^[4]

Height: 30-100 cm

Habit: Low evergreen shrub

Leaves: Narrow, leathery, in-rolled margins, rust-coloured woolly felt beneath, aromatic

Flowers: Small, white, in terminal clusters

Stem: Low, woody, evergreen

Root: Fibrous, shallow root system adapted to boggy ground

Fruit: Small dry capsule

Flowering Period: May-July

Habitat & Distribution

Native to boreal and subarctic wetlands across northern Europe, Asia and North America, growing in acidic peat bogs, wet coniferous forest and tundra margins.^{[1, 4]}

Harvesting

Leaves and young stems are gathered, traditionally in late summer, and dried. Only small amounts are used given the plant's ledol/grayanotoxin content, and correct identification against toxic bog look-alikes (bog rosemary) is essential.^[6]

Parts: Leaf, Stem

Season: Traditionally late summer

Key Constituents

Essential oil (ledol, palustrol)^[2]

Ledol is the characteristic, mildly toxic sesquiterpene alcohol of the leaf, particularly concentrated in fresh material.

Essential (volatile) oilSesquiterpenes

Flavonoids and tannins^[4]

Contribute to antioxidant and astringent activity.

FlavonoidsTannins

Grayanotoxins (diterpenes)^[6]

Toxic diterpenes shared with related Ericaceae; the basis for the caution around excessive or prolonged use.

Pharmacological Actions

Anti-inflammatory^{[1, 2, 3, 4, 11, 13, 14]}

Antioxidant^{[1, 4, 13, 14]}

Diuretic^{[1, 13, 14]}

Traditional & Indicated Uses

Arthritis / joint pain^{[1, 2, 11, 13, 14]}Preliminary · 2/10

inferred from anti-inflammatory action

Evidence: 2

Label: Arthritis / joint pain

more plants for arthritis / joint pain →detailed sources →

Inflammation (general)^{[1, 13, 14]}Preliminary · 1/10

inferred from anti-inflammatory action

Evidence: 1

Label: Inflammation (general)

more plants for inflammation (general) →detailed sources →

Respiratory support^{[1, 6, 13, 14]}Preliminary · 1/10

Evidence: 1

Label: Respiratory support

more plants for respiratory support →detailed sources →

Skin irritation^{[1, 13, 14]}Preliminary · 1/10

inferred from anti-inflammatory action

Evidence: 1

Label: Skin irritation

more plants for skin irritation →detailed sources →

Swelling / fluid retention^{[1, 3, 11, 13, 14]}Limited · 3/10

inferred from diuretic action

Evidence: 3

Label: Swelling / fluid retention

more plants for swelling / fluid retention →detailed sources →

Urinary support^{[1, 13, 14]}Preliminary · 1/10

inferred from diuretic action

Evidence: 1

Label: Urinary support

more plants for urinary support →detailed sources →

Urinary tract infection (UTI)^{[1, 13, 14]}Preliminary · 1/10

inferred from diuretic action

Evidence: 1

Label: Urinary tract infection (UTI)

more plants for urinary tract infection (uti) →detailed sources →

Traditional Use & History

Labrador tea has a long Indigenous North American and Scandinavian folk-medicine tradition as a mild diuretic and respiratory remedy, and as an aromatic tea and spice, always used in small, cautious amounts given its narcotic/toxic potential at higher doses. Modern phytochemical work confirms anti-inflammatory and antioxidant activity of its essential oil.^[1]

Preparations

Infusion (tea)^[6]

Dried leaf steeped briefly in hot water, in small quantities only.

Essential oil (external)^[2]

Used topically or aromatically; not intended for concentrated internal use.

Dosage

Infusion (tea)^{[1, 13, 14]}

Duke (2002) advises using Labrador tea only with caution and at low doses given its narcotic/deliriant potential at higher amounts; it is not appropriate for regular internal use. Educational reference only, not a prescription - use only small, occasional amounts of properly identified leaf.

Safety, Cautions & Contraindications

Safety note^{[1, 13, 14]}Caution

Labrador tea contains ledol, a toxic sesquiterpene alcohol, particularly concentrated in fresh leaves. Excessive consumption can cause dizziness, headache, nausea, and even toxicity (especially in the related Ledum palustre). Use only in small, controlled amounts. Not recommended during pregnancy or breastfeeding. Identify plant correctly - confusion with other bog plants can be dangerous.

Safety note^{[1, 13, 14, 15]}Caution

Duke (2002) rates Labrador tea as + (caution warranted) and notes primarily folkloric activities, with the plant acting as a diuretic, expectorant, and vulnerary. Importantly, Duke classifies it as having narcotic and deliriant potential - large doses can cause intoxication, hallucinations, and toxicity. It contains ericolin and ledol, which are potentially neurotoxic compounds. Duke emphasizes that Labrador tea should be used only with caution and at low doses, and notes that it is not appropriate for regular internal use given its toxicity profile at higher amounts (Duke, 2002).

Dangerous Lookalikes

Andromeda Polifolia^{[16, 17]}Dangerous

Confused Part: Narrow evergreen leaves gathered to brew marsh 'Labrador tea'; toxic bog rosemary shares the same bog habitat and similar narrow evergreen leaves.

Confusion Context: Marsh Labrador tea (Rhododendron tomentosum) is brewed in small amounts as a traditional herbal tea. Bog rosemary (Andromeda polifolia) grows in the same acid bogs and has similar narrow, leathery, evergreen leaves; as bushcraft guidance (Paul Kirtley) warns, it is one of the poisonous bog plants that can be confused with Labrador tea. Bog rosemary contains grayanotoxins, which can cause vomiting, low blood pressure and dangerous slowing of the heart - grayanotoxin poisoning has caused complete heart block. Marsh Labrador tea is itself used only cautiously in tiny doses (it too contains grayanotoxin and ledol), so brewing the wrong bog shrub is a real hazard.

Distinguishing Features: Leaf underside (decisive): marsh Labrador tea has leaves with inrolled margins and a dense rust-coloured woolly felt on the underside, and the crushed leaf is strongly aromatic. Bog rosemary leaves are smooth and pale or whitish underneath, with NO woolly felt and NO aroma., Flowers: bog rosemary has pink, urn-shaped (bell-like) nodding flowers, whereas marsh Labrador tea has clusters of small white flowers., General rule: a bog shrub with narrow evergreen leaves that are smooth and pale beneath and have no smell is NOT Labrador tea.

Key Test: Turn a leaf over and smell it. Marsh Labrador tea has a rusty, woolly felt on the underside of the leaf and a strong aromatic scent. If the underside is smooth and pale with no woolly felt and the leaf has no aroma - especially if the flowers are pink and bell-shaped - it is bog rosemary (or a laurel), which is toxic; do not brew it.

Reviewed By: Omnia Sana (owner-authorized)

Reviewed Date: 2026-07-07

Harvest Readiness

^[12]

Part: leaf

Signals: Gather the leaves with the young flowering shoots at flowering, in spring to early summer.

Basis: traditional

Source Quote: It is in flower from April to June.

Species Confirmed: 1

Notes: PFAF (REF-3326, as Ledum palustre); the medicinal part is 'the leaves and young flowering shoots', gathered at the flowering stage (in flower April-June). Single lineage -> provisional. SAFETY: marsh Labrador tea is TOXIC (ledol/grayanotoxins) and can be confused with the poisonous bog rosemary (Andromeda polifolia) in the same bog habitat - confirm identity; see Dangerous Lookalikes.

^[12]

Part: stem

Signals: Gather the young flowering shoots (leafy stems) at flowering, in spring to early summer.

Basis: traditional

Source Quote: It is in flower from April to June.

Species Confirmed: 1

Notes: PFAF (REF-3326, as Ledum palustre); the young flowering shoots (leafy stems) are the part, gathered at flowering. Single lineage -> provisional. SAFETY: as above - toxic, and confusable with Andromeda polifolia.

External Identifiers

GBIF ›Wikidata ›

References & Sources

Dampc, A. and Luczkiewicz, M (2013) 'Rhododendron tomentosum (Ledum palustre): a review of traditional use based on current research', pp. 130--143. Traditional / reference
https://scholar.google.com/scholar?q=Rhododendron%20tomentosum%20%28Ledum%20palustre%29%3A%20a%20review%20of%20traditional%20use%20based%20on%20current%20research
Jesionek, A., Kokotkiewicz, A., Mikosik-Roczynska, A., Ciesielska-Figlon, K. and others (2019) 'Chemical variability of Rhododendron tomentosum (Ledum palustre) essential oils and their pro-apoptotic effect on lymphocytes and rheumatoid arthritis synoviocytes', Fitoterapia, 139, pp. 104402. doi:10.1016/j.fitote.2019.104402 Preclinical
https://doi.org/10.1016/j.fitote.2019.104402
Kang, J.Y., Tran, K.D., Seiff, S.R., Mack, W.P. and Lee, W.W (2017) 'Assessing the Effectiveness of Arnica montana and Rhododendron tomentosum (Ledum palustre) in the Reduction of Ecchymosis and Edema After Oculofacial Surgery: Preliminary Results', Ophthalmic Plastic and Reconstructive Surgery, 33(1), pp. 47-52. doi:10.1097/IOP.0000000000000645 Clinical study
https://doi.org/10.1097/IOP.0000000000000645
Vengryte, M. and Raudone, L (2024) 'Phytochemical Profiling and Biological Activities of Rhododendron subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere', Plants (Basel), 13(6), pp. 901. doi:10.3390/plants13060901 Traditional / reference
https://doi.org/10.3390/plants13060901
Iunusova, D.R., Polezhaeva, M.A. and Marchuk, E.A (2024) 'Confusing boundaries of the Labrador tea species: dispersal history explains the lack of clear species structure', Annals of Botany, 134(6), pp. 959-974. doi:10.1093/aob/mcae130 Preclinical
https://doi.org/10.1093/aob/mcae130
Dampc, A. and Luczkiewicz, M (2014) 'Labrador tea - the aromatic beverage and spice: a review of origin, processing and safety', Journal of the Science of Food and Agriculture, 95(8), pp. 1577-1583. doi:10.1002/jsfa.6889 Traditional / reference
https://doi.org/10.1002/jsfa.6889
Jaenson, T.G.T., Palsson, K. and Borg-Karlson, A.K (2005) 'Evaluation of extracts and oils of tick-repellent plants from Sweden', Medical and Veterinary Entomology, 19(4), pp. 345-352. doi:10.1111/j.1365-2915.2005.00578.x Preclinical
https://doi.org/10.1111/j.1365-2915.2005.00578.x
Tattje, D.H.E. and Bos, R (1981) 'Composition of essential oil of Ledum palustre', Planta Medica, 41(3), pp. 303-307. doi:10.1055/s-2007-971719 Preclinical
https://doi.org/10.1055/s-2007-971719
Zhang, K., Wang, J., Chen, L., Li, J. and others (2019) 'Two new taraxerane-type triterpenes from Ledum palustre L', Natural Product Research, 34(19), pp. 2723-2728. doi:10.1080/14786419.2019.1586689 Preclinical
https://doi.org/10.1080/14786419.2019.1586689
Islam, M.N., Khalil, M.I., Islam, M.A. and Gan, S.H (2013) 'Toxic compounds in honey', Journal of Applied Toxicology, 34(7), pp. 733-742. doi:10.1002/jat.2952 Traditional / reference
https://doi.org/10.1002/jat.2952
Baananou, S., Bagdonaite, E., Marongiu, B., Piras, A. and others (2014) 'Supercritical CO2 extract and essential oil of aerial part of Ledum palustre L. - Chemical composition and anti-inflammatory activity', Natural Product Research, 29(11), pp. 999-1005. doi:10.1080/14786419.2014.965167 Preclinical
https://doi.org/10.1080/14786419.2014.965167
Plants For A Future 'Ledum palustre (Marsh Labrador Tea, Wild Rosemary)'. Available at: https://pfaf.org/user/Plant.aspx?LatinName=Ledum+palustre Traditional / reference
https://pfaf.org/user/Plant.aspx?LatinName=Ledum+palustre
Grieve, M (1931) 'A Modern Herbal'. Traditional / reference
https://scholar.google.com/scholar?q=A%20Modern%20Herbal
Royal Botanic Gardens, Kew (n.d.). Available at: https://powo.science.kew.org Traditional / reference
https://powo.science.kew.org
Duke, J.A (2002) 'Handbook of Medicinal Herbs, Second Edition'. Traditional / reference
https://scholar.google.com/scholar?q=Handbook%20of%20Medicinal%20Herbs%2C%20Second%20Edition
Kirtley, Paul (2015) 'Labrador Tea - Tonic or Toxic?'. Available at: https://paulkirtley.co.uk/2015/labrador-tea-tonic-or-toxic/ Traditional / reference
https://paulkirtley.co.uk/2015/labrador-tea-tonic-or-toxic/
Jiang, L. and Zhanxiong, L. and Fengcai, Y. and Fuli, L. and Xiaoling, S (2022) 'Third-degree atrioventricular block caused by intoxication with rhododendron leaves', Annals of Noninvasive Electrocardiology, 28(2), pp. e13012. doi:10.1111/anec.13012 Clinical study
https://doi.org/10.1111/anec.13012

Selected studies & references

ClinicalAssessing the Effectiveness of Arnica montana and Rhododendron tomentosum (Ledum palustre) in the Reduction of Ecchymosis and Edema After Oculofacial Surgery: Preliminary Results source↗ (2017)

PreclinicalConfusing boundaries of the Labrador tea species: dispersal history explains the lack of clear species structure source↗ (2024)

PreclinicalChemical variability of Rhododendron tomentosum (Ledum palustre) essential oils and their pro-apoptotic effect on lymphocytes and rheumatoid arthritis synoviocytes source↗ (2019)

PreclinicalTwo new taraxerane-type triterpenes from Ledum palustre L. source↗ (2019)

PreclinicalSupercritical CO2 extract and essential oil of aerial part of Ledum palustre L. - Chemical composition and anti-inflammatory activity source↗ (2014)

PreclinicalEvaluation of extracts and oils of tick-repellent plants from Sweden source↗ (2005)

PreclinicalComposition of essential oil of Ledum palustre source↗ (1981)

TraditionalPhytochemical Profiling and Biological Activities of Rhododendron subsect. Ledum: Discovering the Medicinal Potential of Labrador Tea Species in the Northern Hemisphere source↗ (2024)

All 14 studies in the Knowledge Finder →

Educational use only. This profile summarises traditional and scientific sources for reference. It is not medical advice and not a substitute for a qualified practitioner. Some plants carry safety cautions and drug interactions - always check before use.
This profile is assembled automatically from the Omnia Sana plant database, which we curate by hand. How this site is built.

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