New York Metropolitan Flora

Nomenclature

Ledum L., Sp. Pl. 391. 1753. Gen. Pl. 185. 1754. TYPE: Ledum palustre L. (=Rhododendron tomentosum ssp. subarcticum (Harmaja) G. D. Wallace).

Rhodora L., Sp. Pl., ed. 2, 561. 1762. Gen. Pl. ed. 6, 218. 1764. Hochenwartia Crantz, Inst. Rei Herb. 2: 469. 1766, nom. illeg. (Art. 52.1). TYPE: Rhodora canadense L. (=Rhododendron canadense (L.) Torr.).

Misapplied Names:

Azalea L., Sp. Pl. 1: 150. 1753. Gen. Pl. ed. 5, 75. 1754, nom. rej. TYPE: Azalea procumbens L. (=Loiseluria procumbens (L.) Desv.).

Key to the species of Rhododendron

2. Leaves with dense orange or white pubescence below; corolla deeply cleft and appearing to have separate petals...Rhododendron groenlandicum
2. Leaves without pubescence...I>Rhododendron maximum

3. Stamens 10; corolla irregular, divided nearly to the base...Rhododendron canadense
3. Stamens 5; corolla more or less regular, funnelform...4

4. Stamens not exserted; corolla broadly funnelform...Rhododendron molle -- excluded species
4. Stamens long exserted; corolla narrowly funnelform...5

5. Flowers appearing in mid summer, after the leaves have expanded (essentially all of the leaves unfolded, and the vegetative bud scales absent)...6
5. Flowers appearing before or with the leaves (at least some of the leaves still folded or the vegetative bud scales still present...7

6. Sepals under 1 mm long; pedicels puberulent and glandular...Rhododendron viscosum
6. Sepals 1.6-3 mm long; pedicels glandular but not puberulent...Rhododendron arborescens -- excluded species

7. Flowers yellow or orange...Rhododendron calendulaceum -- excluded species
7. Flowers white to pink...8

8. Floral bud scales glabrous; pedicels without short pubescence and long hairs, usually only with long hairs; leaves glabrous or only sparsely unicellular-pubescent...Rhododendron periclymenoides
8. Floral bud scales densely covered with unicellular hairs; pedicels with both short pubescence and long hairs; leaves abaxially moderately to densely covered with unicellular hairs...Rhododendron prinophyllum

List of Rhododendron Species

References to Rhododendron

• Alexander, E. J. 1926. Azalea viscosa glauca. Addisonia 11: 35-6.
• Alexander, E. J. 1935. Azalea arborescens. Addisonia 19: 17-8.
• Anonymous 1892. Proceedings of the club. Bull. Torrey Bot. Club 19: 139-40.
• Anonymous 1895. Proceedings of the club. Bull. Torrey Bot. Club 22: 281-2.
• Anonymous 1974. Rhododendron ingestion. Hosp. Formulary Management 9: 41.
• Ashe, W. W. 1923. Notes on shrubs of the southeastern states. J. Elisha Mitchell Sci. Soc. 39: 110-1.
• Bao, Y.; Nilsen, E. T. 1988. The ecolophysiological significance of leaf movements in Rhododendron maximum L. Ecology 69: 1578-87.
• Beasley, W. G. 1980. A short guide to the native azalea. Quart. Bull. Amer. Rhododendron Soc. 34(1): 28-30.
• Blazich, F. A. et.al. 1991. Seed germination of Rhododendron catawbiense and Rhododendron maximum: influence of light and germination. J. Environ. Hort. 9: 5-8.
• Boettcher, S. E.; Kalisz, P. J. 1990. Single-tree influence on soil properties in the mountains of eastern Kentucky. Ecology 71: 1365-72.
• Breitfeld, A. 1888. Der anatomische Bau der Blõtter der Rhododendroideae in Beziehung zu ihrer systematischen Gruppirung und zur geographischen Verbreitung. Bot. Jahrb. Syst. 9: 319-79, t. V-I. (In German)
• Britton, Elizabeth G. 1913. Wild plants needing protection. 6. "Wild Azalea" (Azalea nudiflora L.). J. New York Bot. Gard. 14: 79-81, pl. 114.
• Britton, Elizabeth G. 1922. Wild plants needing protection. 14. Great Laurel or Rose Bay (Rhododendron maximum L.). J. New York Bot. Gard. 23: 137-8, pl. 277.
• Cafferty, S.; Jarvis, C. E. 2002. Typification of Linnaean plant names in Ericaceae. Taxon 51: 751-753.
• Carey, J. H. 1994. Rhododendron calendulaceum. ()
• Chamberlain, D. F. 1982. A revision of Rhododendron II: Subgenus Hymenanthes. Notes Roy. Bot. Gard. Edinburgh 39: 209-486.
• Chamberlain, D. et.al. (eds.) (1996): 1996. The genus rhododendron: Its classification and synonymy. Royal Botanic Garden Edinburgh, Edinburgh. , 181 pages. (ISBN 187229166X)
• Chastain, R. A.; Townsend, P. A. 2008. Role of evergreen understory shrub layer in the forests of the central Appalachian Highlands. J. Torrey Bot. Soc. 135: 208-223.
• Clarke, J. H. 1956. A selected list of Rhododendron literature. Quart. Bull. Amer. Rhododendron Soc. 10: 163-8.
• Clinton, B. D.; Vose, J. M. 1996. Effects of Rhododendron maximum L. on Acer rubrum L. seedling establishment. Castanea 61: 38-45.
• Coladoanto, M. 1991. Rhododendron maximum. ()
• Coladoanto, M. 1993. Ledum groenlandicum. ()
• Coladoanto, M. 1992. Rhododendron periclymenoides. ()
• Copeland, H. F. 1943. A study, anatomical and taxonomic, of the genera of Rhododendroideae. Amer. Midl. Naturalist 30: 533-625.
• Cowan, J. M. 1949. A survey of the genus Rhododendron. Rhododendron Yearbook. Royal Horticultural Society 4: 29-58.
• Cowan, J. M. 1950. The Rhododendron leaf: a study of the epidermal appendages. Oliver & Boyd, London. , 120 pages.
• Cox, H. T. 1948. Studies in the comparative anatomy of the Ericales. I. Ericaceae - subfamily Rhododendroideae. Amer. Midl. Naturalist 39: 220-45.
• Cullen, J. 1980. A revision of Rhododendron: I: Subgenus Rhododendron sections Rhododendron and Pogonanthum. Notes Roy. Bot. Gard. Edinburgh 39: 1-207.
• Cullen, J. 1994. Rhododendron inflorescence buds. Rhododendrons, Camellias, Magnolias 46: 20-4.
• Cullen, J.; Chamberlain, D. F. 1978. A preliminary synopsis of the genus Rhododendron. Notes Roy. Bot. Gard. Edinburgh 36(1): 105-26.
• Cullen, J.; Chamberlain, D. F. 1979. A preliminary synopsis of the genus Rhododendron: 2. Notes Roy. Bot. Gard. Edinburgh 37(2): 327-38.
• Cullings, K. W.; Bruns, T. D. 1992. Phylogenetic origin of the Monotropoideae inferred from partial 28S ribosomal RNA gene sequences. Canad. J. Bot. 70: 1703-8. (French summary)
• Czekalski, M. 1995. Rozanecznik olbrzymi: Rhododendron maximum L. Roczn. Dendrol. 43: 5-25. (In Polish; English summary.)
• Davidian, H. H. 1982. The Rhododendron species. Vol. 1, Lepidotes. Timber Press, Portland, Oregon.
• Davidian, H. H. 1989. The Rhododendron species. Vol. 2, Pt. 1, Elepidotes. Timber Press, Portland, Oregon.
• Della-Bianca, L.; McGee, C. E. 1972. Reaction of natural Rhododendron maximum L. to liming in the southern Appalachians. J. Elisha Mitchell Sci. Soc. 88(3): 109-12.
• Dobhal, M. P.; Joshi, Y. C.; Joshi, P. 1991. A review of the genus Rhododendron: part 2. Herba Pol. 37(2): 89-94. (In English; Polish summary)
• Doleshy, F. 1979. Progress in rhododendron classification. Univ. Washington Arbor. Bull. 42(1): 18-9.
• Eberhardt, R. M.; Latham, R. E. 2000. Relationships among vegetation, surficial geology and soil water content at the Pocono mesic till barrens. J. Torrey Bot. Soc. 127: 115-124.
• Fernald, M. L. 1941. Two forms of Rhododendron maximum. Rhodora 43(511): 336.
• Flinn, M. A.; Pringle, J. K. 1983. Heat tolerance of rhizomes of several understory species. Canad. J. Bot. 61: 452-7.
• Flint, E. M. 1918. Structure of wood in blueberry and huckleberry. Bot. Gaz. 65: 556-9.
• Forbes, E. B. 1931. Mountain laurel and rhododendron as food for the white tailed deer. Ecology 12(2): 323-33.
• Forbes, E. B.; Bechdel, S. I. 1930. The chemical composition and feeding value of laurel and rhododendron, and the conditions of browsing in forests overstocked with deer, in relation to the death of young deer. Pennsylvania State Coll. Agric. Exp. Sta. Bull. 258: 39-41.
• Foster, A. S. 1937. Structure and behavior of the marginal meristem in the bud scales of Rhododendron. Amer. J. Bot. 24: 304-16.
• Galle, F. C. 1987. Azaleas. ed. Timber Press, Portland, OR. , 627 pages.
• Glenn, C. T.; Blazich, F. A.; Warren, S. L. 1998. Influence of storage temperatures on long-term seed viability of selected native ericaceous species. J. Environ. Hort. 16: 166-172.
• Glenn, C. T.; Blazich, F. A.; Warren, S. L. 1999. Secondary seed dormancy of Rhododendron catawbiense and Rhododendron maximum. J. Environ. Hort. 17: 1-4.
• Glenn, Steven D. 2001. The rediscovery of Ledum groenlandicum Oeder (Ericaceae) in New Jersey. J. Torrey Bot. Soc. 128: 407-408.
• Goetsch, L.; Eckert, A. J.; Hall, B. D. 2005. The molecular systematics of Rhododendron (Ericaceae): a phylogeny based upon RPB2 gene sequences. Syst. Bot. 30: 616-626.
• Gordon, H. D. 1937. Mycorrhiza in Rhododendron. Ann. Bot. , new series 1 : 593-613.
• Hanna, W. J.; Grant, C. L. 1962. Spectrochemical analysis of the foliage of certain trees and ornamentals for 23 elements. Bull. Torrey Bot. Club 89: 293-302.
• Harborne, J. B.; Williams, C. A. 1971. Leaf survey of flavonoids and simple phenols in the genus Rhododendron. Phytochemistry 10: 2727-2744.
• Hardikar, S. W. 1922. On Rhododendron Poisoning. J. Pharm. and Exper. Therapeutics 20: 17-44.
• Hardin, J. W.; Gensel, W. H. 1982. Atlas of foliar surface features in woody plants, IV. Rhododendron (Ericaceae) of eastern North America. Bull. Torrey Bot. Club 109: 189-98.
• Harmaja, H. 1991. Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species. Ann. Bot. Fenn. 28: 171-3.
• Harmaja, H. 1990. New names and nomenclatural combinations in Rhododendron (Ericaceae). Ann. Bot. Fenn. 27: 203-4.
• Hayes, S.; Keenan, J.; Cowan, J. M. 1951. A survey of the anatomy of the Rhododendron leaf in relation to the taxonomy of the genus. Notes Roy. Bot. Gard. Edinburgh 21: 1-34.
• Hedegaard, J. 1980. Morphological studies in the genus Rhododendron dealing with fruits, seeds and seedlings and their associated hairs. G.E.C. Gads Publ. House, Copenhagen. (2 vols.)
• Hermann, P. M.; Palser, B. F. 2000. Stamen development in the Ericaceae. I. Anther wall, microsporogenesis, inversion, and appendages. Amer. J. Bot. 87: 934-957.
• Hodgdon, A. R.; Pike, R. 1961. An ecological interpretation of Rhododendron colonies in Maine and New Hampshire. Rhodora 63: 61-70.
• Hutchinson, J. 1946. Evolution and classification of Rhododendrons. Rhododendron Yearbook. Royal Horticultural Society 1: 42-7.
• Hutchinson, J. 1947. The distribution of Rhododendrons. Rhododendron Yearbook. Royal Horticultural Society 2: 87-98.
• Iltis, H. H. 1956. Studies in Virginia plants. II. Rhododendron maximum in the Virginia coastal plain and its distribution in North America. Castanea 21: 114-24.
• Irving, E.; Hebda, R. 1993. Concerning the origin and distribution of Rhododendrons. J. Amer. Rhododendron Soc. 47: 139-46, 157-62.
• Janaki Ammal, E. K. 1950. Polyploidy in the genus Rhododendron. Rhododendron Yearbook. Royal Horticultural Society 5: 92-8.
• King, B. L. 1977. Flavonoid analysis of hybridization in Rhododendron section Pentanthera (Ericaceae). Syst. Bot. 2(1): 14-27.
• King, B. L. 1975. The systematic implications of the flavonoids in the deciduous Rhododendron of North America. Ph.D. Dissertation Herbarium (GA)166 p.
• King, B. L. 1977. The flavonoids of the deciduous Rhododendron of North America (Ericaceae). Amer. J. Bot. 64(3): 350-60.
• King, M. J.; Buchman, S. L. 1995. Bumble bee-initiated vibration release mechanism of Rhododendron pollen. Amer. J. Bot. 82(11): 1407-11.
• Kingdon-Ward, F. 1947. Observations on the classification of the genus Rhododendron. Rhododendron Yearbook. Royal Horticultural Society 2: 99-114.
• Knowlton, C. H. 1950. Rhododendron maximum in New England. Rhodora 52(621): 215-8.
• Kron, K. A. 1989. Azalea rosea Loiseleur is a superfluous name. Sida 13: 331-3.
• Kron, K. A. 1993. A taxonomic revision of Rhododendron sect. Pentanthera (Ericaceae). Edinburgh J. Bot. 50(3): 249-364.
• Kron, K. A. 1997. Identifying the native azaleas - Part II. The Azalean 19: 48-50.
• Kron, K. A. et.al. 1998. Using DNA sequences to estimate evolutionary relationships among rhododendrons and azaleas. J. Amer. Rhododendron Soc. 52: 70-72.
• Kron, K. A.; Chase, M. W. 1993. Systematics of the Ericaceae, Empetraceae, Epacridaceae and related taxa based upon rbcL sequence data. Ann. Missouri Bot. Gard. 80: 735-41.
• Kron, K. A.; Judd, W. S. 1990. Phylogenetic relationships with the Rhodoreae (Ericaceae) with specific comments on the placement of Ledum. Syst. Bot. 15: 57-68.
• Kurashige, Y. M. et.al. 1998. Investigation of sectional relationships in the genus Rhododendron (Ericaceae) based on matK sequences. J. Jap. Bot. 73: 143-154.
• Kurashige, Y. et.al. 2001. Sectional relationships in the genus Rhododendron (Ericaceae): evidence from MATK and TRNK intron sequences. Pl. Syst. Evol. 228: 1-14.
• Latham, R. E.; Thompson, J. E.; Riley, S. A.; Wibiralske, A. W. 1996. The Pocono till barrens: shrub savanna persisting on soils favoring forest. Bull. Torrey Bot. Club 123: 330-49.
• Lawrence, G. H. M. 1954. The status of Rhododendron nudiflorum and R. roseum. Baileya 2: 1-2.
• Lee, F. P. 1958. The azalea book. Van Nostrand, Princeton, NJ. , 324 pages.
• Lee, F. P. et.al. (eds.) (1952): 1952. Azalea Handbook. The American Horticulture Society, Washington, DC. , 148 pages.
• Lei, T. T. et.al. 2002. Effects of Rhododendron maximum thickets on tree seed dispersal, seedling morphology, and survivorship. Int. J. Plant Sci. 163: 991-1000.
• Li, H. 1957. Chromosome studies in the azaleas of eastern North America. Amer. J. Bot. 44: 8-14.
• Lipscomb, M. V.; Nilsen, E. T. 1990. Environmental and physiological factors influencing the natural distribution of evergreen and deciduous shrubs on northeast and southwest slopes of the southern Appalachian Mountains. I. Irradiance tolerance. Amer. J. Bot. 77(1): 108-15.
• Lipscomb, M. V.; Nilsen, E. T. 1990. Environmental and physiological factors influencing the natural distribution of evergreen and deciduous shrubs on northeast and southwest slopes of the southern Appalachian Mountains. II. Water relations. Amer. J. Bot. 77(4): 517-26.
• Love, D. 1968. Nomenclatural notes on Mt. Washington plants. Taxon 17: 89.
• Lovell, J. H.; Lovell, H. B. 1932. The pollination of rhodora. Rhodora 34(407): 213-4.
• Luteyn, J. L.; O'Brien, M. E. (eds.) (1980): 1980. Contributions toward a classification of Rhododendron. Proceedings: International Rhododendron conference. The New York Botanical Garden, May 15-17, 1978. New York Botanical Garden, New York. , 338 pages.
• Mackenzie, K. K. 1918. Labrador tea in New Jersey. Torreya 18: 239-242.
• Marchand, P. J. 1975. Apparent ecotypic differences in the water relations of some northern bog Ericaceae. Rhodora 77(809): 53-63.
• McGee, C. E.; Smith, R. C. 1967. Undisturbed rhododendron thickets are not spreading. J. Forest. 65: 334-5.
• McGinty, D. T. 1972. The ecological roles of Kalmia latifolia L. and Rhododendron maximum L. in the hardwood forest at Coweeta. M.S. Thesis Univ. of Georgia, Athens, GA81 p.
• McGraw, J. B. 1989. Effects of age and size on life histories and population growth of Rhododendron maximum shoots. Amer. J. Bot. 76(1): 113-23.
• Ming, T.; Fang, R. 1990. The phylogeny and evolution of genus Rhododendron. Acta Bot. Yunnanica 12(4): 353-65. (In Chinese; English summary)
• Mohlenbrock, R. H.; Richardson, J. W. 1963. Notes on the genus Rhododendron. Castanea 28: 62-6.
• Monk, C. D.; McGinty, D. T.; Day, F. P. Jr. 1985. The ecological importance of Kalmia latifolia and Rhododendron maximum in the deciduous forest of the southern Appalachians. Bull. Torrey Bot. Club 112(2): 187-93.
• Moran, N. C.; Dresel, P. E.; Perkins, M. E.; Richardson, A. P. 1954. The Pharmacological Actions of Andremodotoxin, An Active Princinciple from Rhododendron maximum. J. Pharm. Exp. Therap. 110: 415.
• Morrison, B. Y. 1929. Azaleas and rhododendrons from seed. United States Department of Agriculture Circular 68: 1-8.
• Muller, R. N. 1991. Growing season water relations of Rhododendron maximun L. and Kalmia latifolia L. Bull. Torrey Bot. Club 118: 123-7.
• Nilsen, E. T. 1986. Quantitative phenology and leaf survivorship of Rhododendron maximum in contrasting irradiance environments of the southern Appalachian Mountains. Amer. J. Bot. 73(6): 822-31. (see also Amer. J. Bot. 75(10):1526-1534. 1988.)
• Nilsen, E. T. 1985. Seasonal and diurnal leaf movements of Rhododendron maximum L. in contrasting irradiance environments. Oecologia 65: 296-302.
• Nilsen, E. T. 1987. The influence of temperature and water relations on leaf movements in Rhododenrdon maximum. Pl. Physiol. (Lancaster) 83: 607-12.
• Nilsen, E. T. 1991. The relationship between freezing tolerance and thermotropic leaf movement in five Rhododendron species. Oecologia 87: 63-71.
• Nilsen, E. T. 1990. Why do Rhododendron leaves curl? Arnoldia (Jamaica Plain) 50: 30-5.
• Nilsen, E. T. et.al. 1999. Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause? Amer. J. Bot. 86: 1597-1605.
• Nilsen, E. T. et.al. 2001. Does Rhododendron maximum L. (Ericaceae) reduce the availability of resources above and belowground for canopy tree seedlings? Amer. Midl. Naturalist 145: 325-343.
• Nilsen, E. T.; Stetler, D. A.; Gassman, C. A. 1988. Influence of age and microclimate on the photo-chemistry of Rhododendron maximum leaves. II. Chloroplast structure and photosynthetic light response. Amer. J. Bot. 75(10): 1526-34.
• Olszowy, D. R. 1977. Of bees, rhododendrons and honey. Amer. Bee J. 117: 498-500.
• Palser, B. F. 1986. Rhododendron: an intimate glimse into the flower. J. Amer. Rhododendron Soc. 40: 18-21, 35-44.
• Palser, B. F. 1985. Rhododendron: an intimate glimpse into the flower. Rhododendron 24(4): 52-70.
• Palser, B. F. 1982. Variation in ovary, ovule and megagametophyte of Rhododendron: relation to infrageneric systematics. Bull. New Jersey Acad. Sci. 27(1): 42-3.
• Palser, B. F.; Philipson, W. R.; Philipson, M. N. 1991. Characteristics of ovary, ovule and mature megagametophyte in Rhododendron L. (Ericaceae) and their taxonomic significance. J. Linn. Soc. Bot. 105(4): 289-390.
• Palser, B. F.; Philipson, W. R.; Philipson, M. N. 1985. The ovary, ovule and megagametophyte in Rhododendron. Notes Roy. Bot. Gard. Edinburgh 43(1): 133-60.
• Paratley, R. D. 1986. Vegetation-environment relations in a conifer swamp in central New York. J. Torrey Bot. Soc. 113: 357-371.
• Pearson, V.; Read, D. J. 1973. The biology of mycorrhiza in the Ericaceae. I. The isolation of the endophyte and synthesis of micorrhizas in asceptic culture. New Phyt. 72: 371-9.
• Penhallow, D. P. 1909. An account of certain noteworthy features in the habitat of Rhodora. Rhodora 11: 173-7.
• Petersen, H. E. 1908. The structure and biology of arctic flowering plants. 1. Ericineae (Ericaceae, Pirolaceae). 2. The biological anatomy of the leaves and stems. Meddel. Gronland 36: 75-138.
• Peterson, T. A.; Mueller, W. C.; Englander, L. 1980. Anatomy and ultrastructure of a Rhododendron root-fungus association. Canad. J. Bot. 58: 2421-33.
• Philipson, M. N. 1987. An outline of the history of Rhododendron classification. Bull. Dunedin Rhododendron Group 15: 8-15.
• Philipson, M. N. 1985. The Rhododendron nectary. Notes Roy. Bot. Gard. Edinburgh 43(1): 117-31.
• Philipson, M. N. 1970. Cotyledons and the taxonomy of Rhododendron. Notes Roy. Bot. Gard. Edinburgh 30: 55-77.
• Philipson, W. R. 1985. Shoot morphology in Rhododendron. Notes Roy. Bot. Gard. Edinburgh 43: 161-71.
• Philipson, W. R. 1980. Problems in the classification of the Azalea complex. In: Contributions toward a classification of <em>Rhododendron</em>. New York Botanical Garden, Bronx. , 53-62 pages.
• Philipson, W. R.; Philipson, M. N. 1986. A revision of Rhododendron III: Subgenera Azaleastrum, Mumeazalea, Candiastrum, and Theorhodion. Notes Roy. Bot. Gard. Edinburgh 44: 1-23.
• Philipson, W. R.; Philipson, M. N. 1973. A history of Rhododendron classification. Notes Roy. Bot. Gard. Edinburgh 32(2): 223-38.
• Phillips, D. L.; Murdy, W. H. 1984. Effects of rhododendron (Rhododendron maximum L.) on regeneration of southern Appalachian hardwoods. Forest Sci. 31: 226-33.
• Phillips, D. L.; Murdy, W. H. 1985. Effects of rhododendron (Rhododendron maximum L.) on regeneration of southern Appalachian hardwoods. Forest Sci. 31: 226-33.
• Plocher, A. E.; Carvell, K. L. 1987. Population dynamics of rosebay rhododendron thickets in the southern Appalachians. Bull. Torrey Bot. Club 114: 121-6.
• Postan, C. 1996. The Rhododendron story: 200 years of plant hunting and garden cultivation. Royal Horticultural Society, London. , 224 pages.
• Prince, M. 1981. Our wild eastern treasures: native azaleas. Quart. Bull. Amer. Rhododendron Soc. 35(4): 190-200.
• Prince, M. 1978. Our wild eastern treasures: native azaleas. Amer. Hort. Mag. 57: 13-7.
• Purdy, D. C. 1983. Some notes on reproduction in Rhododendron maximum and Rhododendron minus. J. Amer. Rhododendron Soc. 37(4): 224-5.
• Reader, R. J. 1977. Bog ericad flowers: self-compatibility and relative attractiveness to bees. Canad. J. Bot. 55: 2279-87.
• Reader, R. J. 1978. Contribution of overwintering leaves to the growth of three broad-leaved evergreen shrubs belonging to the Ericaceae family. Canad. J. Bot. 56(10): 1248-61. (See Erratum, Can. J. Bot. 56(14):1711. 1978.)
• Reader, R. J. 1975. Competative relationships of some bog ericads for major insect pollinators. Canad. J. Bot. 53(13): 1300-5.
• Reader, R. J. 1983. Using heatsum models to account for geographic variation in the floral phenology of two ericaceous shrubs. J. Biogeogr. 10(1): 47-64.
• Reader, R. J. 1983. Modelling geographic variation in the timing of shoot extension by ericaceous shrubs. Canad. J. Bot. 61: 2032-7.
• Reader, R. J. 1982. Geographic variation in the shoot productivity of bog shrubs and some environmental correlates. Canad. J. Bot. 60: 340-8.
• Reader, R. J. 1980. Effects of nitrogen fertilizer, shade, and the removal of new growth on longevity of overwintering bog ericad leaves. Canad. J. Bot. 58: 1737-43.
• Reader, R. J. 1979. Flower cold hardiness: a potential determinant of the flowering sequence exhibited by bog ericads. Canad. J. Bot. 57: 997-9.
• Rehder, A. A. 1921. The azaleas of North America. In: A monograph of azaleas. The University Press, Cambride, MA. , 107-96 pages.
• Roane, M. K. 1975. The valid names Rhododendron nudiflorum (L.) Torr. and R. roseum (Loisel.) Rehd. Taxon 24: 540.
• Roane, M. K.; Henry, J. de N. 1983. The species of Rhododendron native to North America. J. Amer. Rhododendron Soc. 37: 137-45, 164-8.
• Roane, M. K.; Henry, J. de N. 1981. The species of Rhododendron native to North America. Virginia J. Sci. 32: 50-63.
• Romancier, R. 1971. Ecology of seedling establishment of Rhododendron maximum in the southern Appalachians. Ph.D. Thesis Duke University, Durham, NC122 p.
• Rouse, J. L.; Craven, L. A. 1995. Current Rhododendron taxonomy. Rhododendron 35: 25-7.
• Sargent, C. S. 1893. Rhododendron. In: Silva of North America. Houghton, Mifflin and Company, Boston. , 143-50 pages.
• Saville, D. B. O. 1969. Interrelationships of Ledum species and their rust parasites in western Canada and Alaska. Canad. J. Bot. 47: 1085-100.
• Sax, K. 1930. Chromosome stability in the genus Rhododendron. Amer. J. Bot. 17: 247-51.
• Schwartz, D. 1978. Rhododendrons: a selected, annotated bibliography. Library of the New York Botanical Garden, New York. , 43 pages. (also pub. in 1975, 46 pp.)
• Seithe, A. 1980. Rhododendron hairs and taxonomy. In: Contributions toward a classification of <em>Rhododendron</em>. New York Botanica Garden, Bronx. , 89-115 pages.
• Seithe, A. 1960. Die Haarformen der Gattung Rhododendron L. und die Moglichkeit ihrer taxonomishen verwertung. Bot. Jahrb. Syst. 79: 297-393. (In German)
• Shinners, L. H. 1962. Rhododendron nudiflorum and R. roseum (Ericaceae) - illegitimate names. Castanea 27: 94-5.
• Sifton, H. B. 1940. Lysigenous air spaces in the leaf of Labrador tea, Ledum groenlandicum Oeder. New Phyt. 39: 75-9.
• Sifton, H. B. 1963. On the hairs and cuticle of Labrador Tea leaves. A developmental study. Canad. J. Bot. 41: 199-207.
• Sinclair, J. 1937. The Rhododendron bud and its relation to the taxonomy of the genus. Notes Roy. Bot. Gard. Edinburgh 19: 267-71.
• Skinner, H. T. 1959. An evaluation of our eastern azaleas. Arbor. Bull. 22: 80-1, 106.
• Skinner, H. T. 1955. In search of native azaleas. Morris Arbor. Bull. 6: 1-10, 15-22.
• Skinner, H. T. 1961. Classification of the native American azaleas.
• Sleumer, H. 1949. Ein System der Gattung Rhododendron L. Bot. Jahrb. Syst. 74: 511-53. (In German)
• Sleumer, H. O. 1980. A system of the genus Rhododendron L. In: Contributions towards a classification of <em>Rhododendron</em>. New York Botanical Garden, Bronx. , 1-18 pages.
• Smith, R. C. 1963. Some aspects of variation in growth and development of Rhododendron maximum L. in western North Carolina. M.S. Thesis NC State, Raleigh, NC,
• Spady, H. A. 1981. Groping for grouping: Rhododendron taxonomy. Quart. Bull. Amer. Rhododendron Soc. 35(4): 212-7.
• Spencer, E. L. 1932. Natural distribution of Rhododendron maximum in New Jersey. Bull. Torrey Bot. Club 59: 401-13.
• Spethmann, W. 1987. A new infrageneric classification and phylogenetic trends in the genus Rhododendron (Ericaceae). Pl. Syst. Evol. 157(1-2): 9-31.
• Sprague, T. A. 1929. The correct spelling of certain generic names. IV. Kew Bull. 1929: 38-52.
• Stanley, O. B. 1931. Fat deposits in certain Ericaceae. Butler Univ. Bot. Stud. 2: 33-41.
• Tolmachev, A. I. 1953. K poznaniju jevraziatskikh vidov rada Ledum. Bot. Mat. Gerb. Bot. Inst. Komar AN SSSR 15: 197-207.
• Uttal, L. J. 1988. Lectotypification of Azalea rosea Loisel. (Ericaceae) and a new combination in Rhododendron periclymenoides (Michx.) Skinners. Sida 13(2): 167-70.
• Valder, P. G. 1971. The life cycle of a Rhododendron. Rhododendron 10(1-2): 3-7, 11-4.
• Ward, F. K. 1935. Rhododendron seeds, with special reference to their classification. J. Bot. 73: 241-7.
• Warming, E. 1908. The structure and biology of arctic flowering plants. 1. Ericineae (Ericaceae, Pirolaceae). 1. Morphology and biology. Meddel. Gronland 36: 1-71.
• Wherry, Edgar T. 1943. The American azaleas and their varieties. Natl. Hort. Mag. 22: 158-66.
• Wilbur, R. L. 1976. Illegitimate names: Rhododendron nudiflorum (L.) Torr. and R. roseum (Loisel.) Rehd. Taxon 25: 178-179.
• Williams, E. G.; Rouse, J. L.; Knox, R. B. 1985. Barriers to sexual compatability in Rhododendron. Notes Roy. Bot. Gard. Edinburgh 43(1): 81-98.
• Willingham, F. F. 1976. Variation and phenological forms in Rhododendron calendulaceum (Michx.) Torrey (Ericaceae). Castanea 41(3): 215-23.
• Willingham, F. F. 1973. A biosystematic study of bloom forms of Rhododendron calendulaceum. Ph.D. Dissertation Wake Forest University,
• Willingham, F. F. 1975. Taxonomy of the flowering forms of Rhododendron calendulaceum. Bull. Amer. Rhododendron Soc. 29: 183-6.
• Wilson, E. H.; Rehder, A. A. 1921. A monograph of azaleas. The University Press, Cambridge, MA. , 219 pages.
• Young, J. A.; Young, C. G. 1992. Rhododendron. In: Seeds of Woody Plants in North America. Dioscorides Press, Portland. , 297-8 pages.