New York Metropolitan Flora

Rhododendron groenlandicum (Oeder) Kron & Judd - Labrador Tea

Rhododendron groenlandicum
Rhododendron groenlandicum (Oeder) Kron & Judd

Labrador Tea

Photo © Brooklyn Botanic Garden. Photo by George Kalmbacker.

Native , Rare

By Steven Clemants

Not peer reviewed

Last Modified 01/25/2013

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Rhododendron groenlandicum
= Ledum groenlandicum Oeder

Common Names

Labrador Tea

Field Identification

A rare evergreen shrub of bogs with dense orange tomentum on the lower leaf surface.

Food uses

Disclaimer: The information provided here is for reference and historical use. We do not recommend nor do we condone the use of this species for food purposes without first consulting a physician.

(Hedrick, 1972) (Uphof, 1968)

The leaves were used as a tea during the revolution and to "render beer heady".


Poisonous properties

Disclaimer: The information provided here is for reference and historical use. If you believe you have been poisoned, please contact the Poison Control Office near you (look for the number in the front of the phone book).

(Hare et al., 1905)

May contain andromedotoxin. See Kalmia latifolia.

Nomenclature

*Ledum groenlandicum Oeder, Fl. Danica 4: 5, t. 567. 1777. *Ledum palustre ssp. groenlandicum (Oeder) Hultén, Acta Univ. Lund, n.s. 44(1): 1219. 1948. *Rhododendron groenlandicum (Oeder) Kron & Judd, Syst. Bot. 15(1): 67. 1990. TYPE: Greenland. Collector unknown (Holotype: C).

*Ledum palustre var. latifolium C. F. Ludw., Neu. Wilde Baumz. 26. 1783, nom. inval. (Art. 32.1c). *Ledum latifolium Jacq., Collectanea 2: 308. 1788. TYPE: Type not cited.

*Ledum canadense Lodd., Bot. Cab. 11: t. 1049. 1825. TYPE: Type not cited.

*Ledum latifolium var. globosum Mast., Gard. Chron., ser. 2, 9: 698, fig. 124. 1878. TYPE: Type not cited.

*Ledum groenlandicum var. aridiphilum D. Löve, Taxon 12: 89. 1968. TYPE: United States. New Hampshire: Mt. Washington. Löve and Löve 7542 (Holotype: COLO). [dwarf]

Description

HABIT perennial, evergreen, chamaephyte, shrubs, autotrophic, monoclinous, with adventitious roots or with fibrous roots, 0.2-1 m tall, not modified or with rhizomes.

STEMS erect or ascending, round, not winged, "regular". Prickles absent. Bark smooth or striate, not exfoliating, black or dark gray. Branches erect, dark violet-red, round, not winged, 3-4 mm in diam. Twigs reddish orange or reddish violet, not odoriferous, angled, 1.3-2 mm in diam., smooth, hairs short and unbranched and hairs long and unbranched, erect or spreading, multicellular, uniseriate or multiseriate, white or orange, dense, throughout, not glabrescent, glands present or without glands, glands sessile, yellow. Pith present, light yellow, round, continuous, nodal diaphragm absent. Thorns absent. Aerial roots absent. Sap translucent. Resin absent.

LEAVES alternate, 1 per node, crowded toward stem apex, divergent from stem, simple. Stipules absent. Leaves petiolate, petiole "typical", 0.2-0.4 cm long, hairs long and unbranched, erect (curled), multicellular, uniseriate, moderately dense, throughout, not glabrescent, glands present, glands sessile. Leaf: abaxial surface orange or dark yellowish orange, adaxial surface dark green, blades narrowly elliptic or lanceolate, revolute only at margin, symmetric, 2.3-5 cm long, 0.5-1.1 cm wide, coriaceous, base acute, margin ciliate, apex acute, abaxial surface hairs long and unbranched, spreading (curled), multicellular, uniseriate, orange, dense, throughout, not glabrescent, glands present, glands sessile, orange or yellowish orange or orange-yellow, adaxial surface hairs long and unbranched, spreading, multicellular, uniseriate, white or light gray, sparse, throughout, glabrescent, glands present, glands sessile, light yellow. Hyphodromous venation or reticulodromous venation, veins 1. Leaf lobes absent. Spines absent. Tendrils absent.

INFLORESCENCES monomorphic, regular or, if dimorphic, female inflorescence simple, corymbose raceme, terminal. Peduncle absent. Rachis absent, with bracts. Bracts sessile, blades: abaxial surface orange, adaxial surface orange, lanceolate, involute, 3.6-4 mm long, 1.4-2.2 mm wide, base truncate, margin ciliate, apex acute, abaxial surface glabrous, glands present, glands sessile, yellow, adaxial surface glabrous, without glands. Pedicel 10-14 mm long, hairs short and unbranched, hairs erect, unicellular, uniseriate, white or light gray, dense, throughout, not glabrescent, glands present, glands sessile, yellow. Bracteoles 2, sessile, at base of pedicel, not connate, bracteoles: abaxial surface orange, bracteole: adaxial surface orange, narrow oblong, involute, 6.7-8 mm long, 0.2-0.5 mm wide, base truncate, margin ciliate, apex acute. Cupules absent.

FLOWERS serotinous, formed on long shoots, monomorphic, with sepals and petals readily distinguishable from one another, bisexual. Perfect or female flowers white, 5-merous, 6.1-8 mm long, 5.5-10 mm wide, 15-19 flowers per inflorescence, fragrance present, perianth of two whorls. Calyx present, actinomorphic, acetabuliform, of fused sepals, persistent, abaxial and adaxial surfaces the same color, orange-yellow, uniform, 0.5 mm long, 1-1.9 mm wide, tube 0.2-0.3 mm long, calyx limb 0.2-0.3 mm long, 1-1.9 mm wide. Sepals or sepal lobes 5, depressed ovate or narrowly transversely oblong, 0.3-0.5 mm long, 0.9-1 mm wide, base truncate, margin glandular ciliate, apex obtuse, abaxial surface hairs short and unbranched, erect, unicellular, uniseriate, light yellow, moderately dense, basally, not glabrescent, glands present or without glands, glands sessile, yellow or white, adaxial surface glabrous, without glands. Epicalyx absent. Corolla present, actinomorphic, spreading, of free petals, deciduous, abaxial and adaxial surfaces the same color, white, 6.1-8 mm long, 5.5-10 mm wide. Petals or petal lobes 5, "normal", obovate, 4.2-5.5(-7) mm long, 2.2-2.6(-4) mm wide, base cuneate, margin undulate, apex obtuse, abaxial surface glabrous, without glands, adaxial surface glabrous, without glands. Gynoecium syncarpous. Carpels 5. Stigmas 1, truncate. Styles persistent, 1, 2.9-3.2 mm long. Ovary superior, 1-1.5 mm long, 1 mm wide, nectiferous disk present. Locules 5. Placentation apical axile. Stamens 6 to 8, 6-6.5 mm long. Anthers oblong, opening by pores, opening 1/4 of entire anther, bithecal, light orange-yellow, glabrous. Filaments free, S-curved, light orange-yellow, hairs short and unbranched, erect, multicellular, uniseriate. Staminodes absent.

FRUITS septicidal capsule, dark reddish violet, ellipsoid, 3.7-6.5 mm long, 1.9-2.9 mm wide, hairs short and unbranched, appressed, unicellular, uniseriate, white, moderately dense, throughout, not glabrescent, glands present, glands sessile, yellow, dehiscing from the basal end.

SEEDS many, light orange-yellow, linear, 1.2-1.9 mm long, 0.2-0.3 mm wide, wingless, tailed, lineate.

Habitat

(Saville, 1969), (Wherry, 1920)

Open sphagnum bogs and larch swamps, occasionally in closed coniferous forests of high humidity, in soil of pH 4.5-6.

Rarity Status

Heritage global rank -- G5

Connecticut -- Threatened

New Jersey -- (Heritage rank: SX.1)

New York -- Not listed

Species Biology

Flowering

May [week 4] - June [week 3].

Pollination

(Lovely & Lovely, 1936) (Pojar, 1974) (Reader, 1975) (Reader, 1977)

Autogamy -- Autogamy is possible but usually not very effective.

Melittophily -- Flowers are visited by small, short-tongued bees and bumble bees. Most notably Andrena vicina Sm. Other visitors include: Andrena hippotes Rob., Apis mellifera L., Bombus affinis Cr., B. borealis Kby., B. fervida (F.), B. griseocollis (DeG.), B. impatiens Cr., B. rufocinctus Cr., B. ternarius Say, B. terricola Kby., B. vagans Sm., and Osmia atroventris Cr.

Diptera -- Syriphid flies, small museid flies, beeflies, including: Cheilosia leucoparea Loew and Neomyia cornicina (Fab.).

Lepidoptera -- Vanessa atalanta (L.) and Hemaris thysbe (Fab.).

Coleoptera -- Agriotes stabilis (Lec.).

Fruiting

July [week 1] - August [week 4].

Dispersal

(Pojar, 1974)

Anemochory.

Germination

(Morrison, 1929)

Germinable?: Seeds sowed on acidic sandy soil, grown in the shade, and watered from beneath did well.