Practical ecological knowledge for the temperate reader.

Labrador Tea - Rhododendron groenlandicum

Family: Ericaceae (Crowberry family) [E-flora]


Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid soils and can grow in very acid soils.
It can grow in full shade (deep woodland) semi-shade (light woodland) or no shade. It prefers moist or wet soil.[PFAF]
Origin Status: Native [IFBC-E-flora]
General: Erect shrub; stems 0.5-1.5 m tall, rusty soft-hairy. [IFBC-E-flora]
Leaves: Alternate, evergreen, leathery, oblong to lance-oblong or elliptic, (1.2) 2-6 cm long, 3-15 mm wide, margins strongly to slightly rolled under, tips blunt, upper surface deep green, appearing somewhat wrinkled, glabrous to slightly reddish soft-hairy, copiously rusty or yellowish soft-hairy beneath; stalks 1-5 mm long.[IFBC-E-flora]
Flowers: In terminal umbrella-like clusters; flower stalks (0.6) 1.2-2.5 cm long, with short, white hairs (rarely with a few contorted, reddish hairs), often glandular, curved in fruit; corollas white, wheel-shaped, 10-12 mm across, the 5 distinct petals spreading, oblong, and 5-8 mm long; calyces less than 1 mm long, minutely white-hairy on margins, sometimes glandular; stamens 5-8, slightly exceeding the styles, filaments glabrous or sometimes hairy at the base.[IFBC-E-flora]
Fruits: Capsules, narrowly egg-shaped, 4-7 mm long, minutely hairy.[IFBC-E-flora]
Habitat: Bogs and moist to wet forests in the lowland and montane zones.[IFBC-E-flora] Cold bogs and montane coniferous woods[4, 50]. [PFAF]
Range: common throughout most of BC, infrequent in SC BC; N to AK, E to NF, and S to OR, MN, PA, and NJ.[IFBC-E-flora] Eastern and Northern N. America to Greenland. A rare garden escape in Britain.[PFAF]


"In our experience Labrador tea is as safe as regular tea or coffee, but it is said by some to produce drowsiness. We have never experienced such an effect, which may be due to physiological sensitivity in certain individuals or may in some cases be purely psychological. In any case, we recommend that you drink the tea only in moderate quantities and in low concentrations; do not boil the leaves for longer than 10 minutes." [Coffee]

Edible Uses

L. groenlandicum was used by virtually all indigenous peoples of B.C. [Turner, Kuhnlein]

Other Uses

Medicinal Uses


Essential Oil - Source: Leaves - Key constituents: [Tisserand EOS]

  • Sabinene 15.7%
  • Terpinen-4-ol 7.6%
  • b-Selinene 5.7%
  • Myrtenal 3.5%
  • Bornyl acetate 3.3%
  • g-Elemene 3.1%
  • g-Terpinene 2.9%
  • b-Pinene 2.3%
  • Pinocarvone 2.3%
  • a-Caryophyllene 2.2%
  • a-Pinene 1.9%
  • a-Selinene 1.9%
  • Cuminaldehyde 1.6%
  • Camphene 1.5%
  • (Z)-Carveol 1.5%
  • a-Terpinene 1.5%
  • p-Cymene 1.3%
  • (þ)-Limonene 1.1%

Flower Essential oil, % on fresh wt: 0.058 [LLCEOPS]

Whole Plant Essential oil, %: 0.013 [LLCEOPS]

Essential oil (hydrodistillation), % on fresh wt: [LLCEOPS]
Saponification value, mg KOH: 28.81; after acetylation, mg KOH: 97.2
Bound alcohols, %: 7.24; Free alcohols, %: 11.7
Ethers, %: 9.32

Crude Extract

"Our team has previously reported the phytochemical characterization of Labrador tea crude ethanolic extract [59]. In that study, we identified (+)-catechin (9), (−)-epicatechin (10), chlorogenic acid (50), myricitin (51), procyanidin B2 (52), procyanidin A1 (53) and several quercetin glycosides (quercetin-3-O-glucoside (45), quercetin-3-O-galactoside (46); rutin (25) and quercetin-3-O-rhamnoside (54))." [Jetter PBFA]


"In our screening studies, it stimulated glucose uptake in muscle cells, but more importantly induced adipogenesis as strongly as the reference drug rosiglitazone [8]. This would mean less free fatty acids circulating and accumulating in insulin-sensitive tissues such as the liver and the muscle. Such activity is also associated with an improvement of insulin sensitivity." [Jetter PBFA]

Activities (Labrador Tea) — [HMH Duke]

  • Abortifacient (f; PHR; PIP);
  • Analgesic (f; DEM);
  • Antiinflammatory (f; KOM; PH2);
  • Antitussive (f; KOM);
  • Aperitif (f; DEM);
  • Astringent (1; APA); [HMH Duke][HuronSmith Zuni]
  • Deliriant (1; APA);
  • Depurative (f; DEM);
  • Diaphoretic (f; KOM; PIP);
  • Diuretic (f; DEM; KOM; PIP); [HMH Duke][Smith(1927)]
  • Emetic (f; DEM; KOM; PIP);
  • Expectorant (f; PH2; PNC);
  • Hemostat (1; APA);
  • Narcotic (1; APA);
  • Pectoral (f; PNC); [HMH Duke][HuronSmith Zuni]
  • Tonic [HuronSmith Zuni]
  • Vulnerary (1; APA).


"Requires a lime-free loam or peaty soil[1, 11]. Prefers a moist humus-rich acid soil in shade or semi-shade[200]. Plants flower more freely when grown in a sunny position. Plants grow better if they have certain fungal associations in the soil. The best way of providing this is to incorporate some soil from around well-growing established plants into the soil for the new plant[200]. Hardy to at least -15°c[200]. The leaves and the flowers are very aromatic[182, 245]. Plants benefit from removing the dead flowers before they set seed[188]. This prevents them putting too much energy into seed production at the expense of more flowers and leaves. This species is considered by some botanists to be no more than a sub-species of L. palustre[11, 50]. A good bee plant[4]." [PFAF]


"Seed - surface sow in a shady part of the greenhouse in February or March[78, 113]. Another report says that the seed is best sown in the autumn as soon as it is ripe[188]. Germination is variable and can be quite slow. Prick out the seedlings into individual pots as soon as they are large enough to handle and grow the pots on in a shady frame for 18 months before planting them out into their permanent positions[78]. Cuttings of half-ripe wood, 5 - 8cm with a heel, July/August in a frame. Plant out in spring. Fair percentage[78]. Cuttings of mature wood, November/December in a frame[113]. Layering in the autumn. Takes 12 months[78]. Division." [PFAF]

Medicinal Harvesting:
"Harvesting of medicinal plants from wild populations is increasing worldwide, however, studies on sustainable harvesting techniques are lacking. In this exploratory study, we investigated the impact of leaf harvesting on (Oeder) Kron & Judd, a North American temperate shrub, used traditionally as a medicinal plant by the Cree Nation. The species is widely distributed, but Crees are worried that commercial harvesting could threaten local plant populations. Our study was conducted near the Cree Nation of Mistissini (James Bay, Northern Quebec). Three leaf harvest regimes were tested in 2008 and 2009: no harvest, all leaves harvested, and only old leaves harvested; each treatment was performed on 30 plants. The harvesting of all leaves had a negative impact on stem elongation after the first harvest, while leaf production and stem radial growth decreased after the second harvest. Two-thirds of the plants also died following the second regime of harvesting all leaves. The harvesting of old leaves had no significant impact on growth, leaf production, or survival of R. groenlandicum, even after 2 years of harvest. These results lead to the conclusion that sustainable harvest of this species is possible, but further study is required to make definite recommendations." [MedHarvesting]

Allelopathy - N Transformations Under Ledum palustre

"Ledum palustre and Ledum groenlandicum are late successional evergreen shrubs widely distributed in boreal ecosystems that are known to inhibit the growth of P. mariana and Picea glauca when they dominate the understory (Cole et al. 2003; Inderjit and Mallik 1996b). " [Zeng ASA]

"This interference has been related to the presence of plant secondary metabolites (Inderjit and Mallik 1997).... amendments of L. groenlandicum foliage and litter have been found to increase concentrations of phenolic compounds in the soil.... Mineral soils sampled under L. palustre canopy had a lower net N mineralization and N-to-C mineralization ratio, and a higher C mineralization compared to control soils, which was caused by higher gross ammonium immobilization rates (110.6% increase) compared to Ledum-free sites. ...soils sampled under L. palustre and amended with leachate showed similar responses. Thus, C compounds leached from L. palustre stimulated microbial activity when microbes use them as a substrate resulting in increases in soil N immobilization and decreases in N availability for vegetation." [Zeng ASA]

"...mild fires, clearcutting, or heavy spruce budworm defoliation in nutrient-poor black spruce or balsam fir (Abies balsamea (L.) Mill.) Kalmia forest can convert the forest community into Kalmia heath, and it can last for a very long time. If, on the other hand, the understory is predominantly Labrador tea (Ledum groenlandicum Oeder.), the growth inhibition of black spruce may last for 6-10 years, and after that the black spruce may regain the canopy dominance [47]." [Mallik CEP]


Family: Ericaceae - Heath

Shrub to tree, glabrous, hairy, and/or with glandular scale-like hairs. Stem: prostrate to erect, bark thin, sometimes peeling or shredding. Leaf: alternate, evergreen or deciduous, ovate to obovate to elliptic, margin entire, flat to rolled under. Inflorescence: raceme, 1–many-flowered, bracts green to red-brown. Flower: sepals, petals generally 5, corolla radial to bilateral, 1–5 cm, petals free to ± fused, spots or blotch present or 0; anther awns 0; ovary superior. Fruit: capsule, septicidal, dehiscing base to tip or tip to base, placentas axile. Seed: many, fusiform, ± flat to not, wings and/or tails present or 0.
± 1000 species: northern hemisphere, tropical Asia, to Australia. (Greek: rose tree)
Unabridged references: [Chamberlain 1982. Notes Roy. Bot. Gard. Edinburgh 39:209–486; Cullen 1980 Notes Roy. Bot. Gard. Edinburgh 39:1–207] [Jepson]

Local Species;

  1. Rhododendron albiflorum - white-flowered rhododendron [E-flora][PCBC][TSFTK]
  2. Rhododendron groenlandicum - Labrador tea [E-flora][PCBC][TSFTK]
  3. Rhododendron macrophyllum - Pacific rhododendron [E-flora][PCBC][TSFTK]

A shade-tolerant/intolerant, montane to alpine, Western North American deciduous shrub distributed more in the Cordilleran than the Pacific region. Occurs predominantly in continental subalpine boreal climates on moderately dry to fresh, nitrogen-poor soils (Mor humus forms); its occurrence increases with increasing continentality and decreases with increasing latitude. Common and often dominant on water-shedding sites in open­canopy coniferous forests in the coast-interior ecotone; often on decaying coniferous wood. Typically associated with Barbilophozia floerkei, B. lycopodioides, Rhytidiopsis robusta, and Vaccinium membranaceum. An oxylophytic species characteristic of subalpine continental forests.(IPBC)[E-flora]

Habitat / Range
Dry to wet forests and openings in the montane and subalpine zones; common in C and S BC; E to SW AB, and S to OR and W MT.

Habitat / Range
Mesic to moist forests in the lowland and montane zones; locally frequent in the Cascade Mountains, rare on S Vancouver Island; S to MT and N CA.[IFBC-E-flora]

Uses of Related Sp.


Page last modified on Wednesday, March 9, 2022 4:49 AM