Rhododendron maximum L. - Great Laurel, Rose-bay
Native , Occasional
By Steven Clemants
Last Modified 01/25/2013
Common NamesGreat Laurel, Rose-bay
Medicinal usesDisclaimer: The information provided here is for reference and historical use. We do not recommend nor do we condone the use of this Rhododendron maxima for food purposes without first consulting a physician.
The leaves are used to treat rheumatism
Other usesThe wood has been used for handles and as a substitute for boxwood in engraving. The wood of the roots is made into tobacco pipes.
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.
Contains andromedotoxin, a toxic diterpene causing slow pulse, lowering of blood presure, lack of coordination, convultions, progressive paralysis, and death. Arbutin, a glycoside of hydroquinone, is also present and indicated in the poisoning (Hardin & Arena, 1974).
Nomenclature*Rhododendron maximum L. Sp. pl. 1: 392. 1753. LECTOTYPE: USA, Virginia, Collinson s.n. [according to Chamberlain, 1982.].
*Rhododendron Proceum Salisbury, Prodr. Stirp. Chap. Allert. 287. 1796. [superfluous name] TYPE: same as R. maximum L.
*Rhododenrdon maximum à roseum Pursh, Fl. Amer. sept. 1: 297. 1814. TYPE: several elements including  "à. In the mountains, near rivulets and lakes: Canada to Carolina.";  R. maximum Schmidt. arb. t. 121.;  Bot. Mag. 951. bona. and  Lam. illustr. 364. [leaves elliptic-oblong, flowers rose-white]
*Rhododendron maximum album Pursh, Fl. Amer. sept. 1: 297. 1814. ¤Rhododendron album (Pursh) Hoffmannsegg, Verz. Pflanzenkult. 105, 192. 1824. *Rhododendron maximum f. album (Pursh) Fernald, Rhodora 43: 336. 1941. TYPE: " . In shady cedar swamps of New Jersey and Delaware." [leaves cuneate-lanceolate, flowers white]
*Rhododendron maximum purpureum Pursh, Fl. Amer. sept. 1: 297. 1814. *Rhododendron purpureum (Pursh) G. Don., Gen. Hist. Dichlam. Pl. 3: 843. 1834. *Rhododendron maximum f. purpureum (Pursh) Fernald, Rhodora 43: 336. 1941. TYPE: " . On the highest mountains of Virginia and Carolina, near lakes." [flowers purple]
¤?Rhododendron latifolium Hoffmannsegg, Verz. Pfl.-Kult. Nachr. 2: 195. 1826.
*Rhododendron purshii G. Don., Gen. Hist. Dichlam. Pl. 3: 843. 1834. TYPE: cites R. maximum album Pursh as synonym. USA, Cedar swamps in New Jersey and Delaware [fide Chamberlain, 1982].
¤Rhododendron maximum var. albiflorum Rafinesque, Autik. Bot. 86. 1840, nom.
*Rhododendron ashleyi Coker, J. Elisha Mitchell Sci. Soc. 51: 189, t. 53, 54. 1935. TYPE: USA, N Carolina, Ashe Co., 2 miles from Lansing, 19 Jun 1935, 29 Jun 1935, 2 Jul 1934, May 1932 and Sep 1932, Raymond F. Ashley s.n. [19 Jun 1935 specimen fide Chamberlain, 1982].
DescriptionPLANTS: Perennial, evergreen, phanerophyte, shrub, autotrophic, monoclinous, with fibrous roots, 2-10 m tall.
STEMS, BRANCHES, TWIGS: Ascending to erect, round, not winged, "regular". Prickles absent. Bark smooth, not exfoliating, dark orange-yellow. Branches erect to ascending, dark gray, round, not winged, 5-7 mm in diam. Twigs dark orange-yellow, not odoriferous, round, 0.3-0.5 mm in diam., smooth, hairs short and unbranched, appressed, unicellular, uniseriate, white, moderately dense, throughout, glabrescent, without glands. Pith present, light orange-yellow, round, continuous. Thorns absent. Aerial roots absent. Sap translucent. Resin absent.
BUDS: Vascular Bundle Scars 1
LEAVES: Alternate, 1 per node, crowded toward stem apex, divergent from stem, simple. Stipules absent. Leaves petiolate, petiole "typical", 2.2-3.2 cm long, hairs short and unbranched, erect or appressed or spreading, unicellular or multicellular, uniseriate or multiseriate, moderately dense, throughout, glabrescent, glands present and without glands, glands at apex of hairs. Leaf: abaxial surface light greenish yellow; adaxial surface green; blades narrowly elliptic, plane, symmetric, 10.2-19.2 cm long, 3-5.5 cm wide, coriaceous, base obtuse, margin entire; apex acute; abaxial surface hairs short and unbranched, appressed, unicellular, uniseriate, light yellowish orange, moderately dense, throughout, glabrescent, without glands; adaxial surface glabrous, without glands. Veins 1. Spines absent. Tendrils absent.
INFLORESCENCES: Monomorphic, regular or, if dimorphic, female inflorescence simple, raceme (?), terminal. Peduncle present, 0.6 cm long. Rachis present, 2-4 cm long, with bracts. Pedicel 20-33 mm long, hairs short and unbranched, hairs erect or appressed, unicellular or multicellular, uniseriate or multiseriate, light orange, moderately dense, throughout, not glabrescent, glands present and without glands, glands at apex of hairs, dark orange. Bracteoles 2, sessile, at base of pedicel; not connate, bracteoles: abaxial surface orange, adaxial surface orange, linear, plane, 0.8 mm long, 0.02 mm wide, base truncate, margin entire, apex acuminate. Cupules absent.
FLOWERS: Serotinous, formed on long shoots, monomorphic, with sepals and petals readily distinguishable from one another, bisexual. Perfect or female flowers light red, 5 merous, 25-30 mm long, 35-50 mm wide, 11-25 flowers per inflorescence, perianth of two whorls. Calyx present, zygomorphic, campanulate, of fused sepals, persistent, abaxial and adaxial surfaces the same color, white or light red, 5 mm long, 10 mm wide, tube 1.2 mm long, calyx limb 2.5-3.7 mm long, 2.3-4 mm wide. Sepals or sepal lobes 5, very widely ovate, 2.5-3.7 mm long, 2.3-4 mm wide, base acute, margin glandular ciliate. Apex acute or obtuse. Abaxial surface hairs short and unbranched, erect or appressed or spreading, unicellular or multicellular, uniseriate or multiseriate, light orange or light red, moderately dense, throughout, not glabrescent, glands present or without glands, glands at apex of hairs; dark orange; adaxial surface glabrous, without glands. Epicalyx absent. Corolla zygomorphic, campanulate, of fused petals, deciduous, abaxial and adaxial surfaces the same color, light red, 25-30 mm long, 35-50 mm wide, corolla limb 1.5 mm long, 4 mm wide. Petals or petal lobes 5, "normal", very widely obovate, 12 mm long, 12 mm wide, base cuneate, margin entire; apex obtuse; abaxial surface glabrous, without glands; adaxial surface glabrous, without glands. Gynoecium syncarpous. Carpels 5. Stigma 1, capitate. Style persistent, 1, 20 mm long. Ovary superior, 5 mm long, 4 mm wide, nectiferous disk present (?). Locules 5. Placentation axile. Androecium obdiplostemonous. Stamens 10, 15-21 mm long. Anthers obovoid, opening by pores, opening 1/4 of entire anther, bithecal, dark orange-red, glabrous. Filaments free, straight or S-curved (slightly), light reddish orange, hairs short and unbranched, erect, unicellular, uniseriate. Staminodes absent.
FRUITS: Septicidal capsule, dark orange-red, narrow ovoid, 12-17 mm long, 5-6 mm wide, hairs short and unbranched, erect, multicellular, multiseriate, dark violet-red or black, moderately dense, throughout, not glabrescent, glands present, glands at apex of hairs, dark orange.
SEEDS: Seeds many, light reddish orange, oblong, 1.2-1.5 mm long, 0.4-0.5 mm wide, winged, striate.
HabitatMesic and moist woods to swamps.
Indigenous to eastern North America
CT, DC, GA, KY, MA, ME, NC, NH, NJ, NY, OH, PA, RI, SC, TN, VA, VT, WV
Heritage global rank -- G5
Connecticut -- Not Listed
New Jersey -- Not Listed
New York -- Not Listed
(May [week 3]) June [week 3] - July [week 3]
June [week 4] - November [week 1]