New York Metropolitan Flora

Rhododendron prinophyllum (Small) Millais - Early Azalea

Native , Rare

By Steven Clemants

Not peer reviewed

Last Modified 01/25/2013

Back to Rhododendron

Rhododendron prinophyllum

Common Names

Early Azalea

Field Identification

Spring-flowering deciduous shrub with elliptic leaves, funnelform flowers, and pubescent floral bud scales.

Common names

Early Azalea

Election Pink

Mountain Azalea

Rose-Shell Azalea

Rose-Honeysuckle

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).

(Olszowy, 1977)

May produce poisonous honey.

Nomenclature

*Azalea prinophylla Small, N. Am. Fl. 29: 42. 1914, nom. illeg. (Art. 14.4). *Rhododendron prinophyllum (Small) Millais, Rhodod. 229. 1917. TYPE: United States. Pennsylvania: Monroe Co.; Pocono Summit, 22 May 1889, T.C.Porter s.n. (Lectotype NY!; Isolectotypes: NY!) selected by (Kron, 1993).

*Rhododendron roseum f. plenum Rehder, Contr. Gray Herb. 165: 10. 1947. TYPE: Cultivated in the garden of R. H. P. Jacobus, originally found wild in the neighboring woods. 23 Jul 1935, R. H. P. Jacobus, s.n. (Holotype A! #00015330).

*Rhododendron roseum f. albidum Steyerm., Rhodora 62: 131. 1960. TYPE: United States. Missouri: Ste. Genevieve Co.; east of Chimney Rocks, 5 mi E of Pickle, 24 May 1933, J. A. Steyermarck 8522 (Holotype: MO; Isotypes: MINN, MO).

Misapplied Names

*Azalea canescens Michx., Fl. Bor.-Amer. 1: 150. 1803, nom. illeg. (Art. 14.4). *Azalea rosea Loisel. in Duhamel, Traité Arbr. Arbust., 5: 224, t. 64. 1812, nom. illeg. (Art. 14.4). *Rhododendron canescens (Michx.) Porter, Bull. Torrey Bot. Club 16: 220. 1889, nom. illeg. (Art. 53.1). *Rhododendron roseum (Loisel. in Duhamel) Rehder ex E. H. Wilson & Rehder, Monogr., Azaleas 138. 1921. *Rhododendron nudiflorum var. rosea (Loisel. in Duhamel) Wieg., Rhodora 26: 4. 1921. TYPE: United States. South Carolina: A. Michaux s.n. (Lectotype: P) selected by (Kron, 1993). Duhamel's t. 64 was selected as the lectotype of A. rosea by(Uttal, 1988).

Description

HABIT perennial, deciduous, phanerophyte, shrubs or trees (small), autotrophic, monoclinous, with fibrous roots, 1.2-3 m tall, not modified or with rhizomes (rare).

STEMS erect, round, not winged, "regular". Prickles absent. Bark striate, not exfoliating, dark gray. Branches erect or ascending (?), dark gray, round, not winged, 2.5-4 mm in diam. Twigs dark orange-red or yellowish orange or dark yellowish orange or dark orange-yellow, not odoriferous, round, 0.6-1.2 mm in diam., smooth, hairs short and unbranched or hairs long and unbranched, erect and appressed, unicellular and multicellular, uniseriate and multiseriate, white, moderately dense, throughout, glabrescent, without glands. Pith present, light reddish orange, round, continuous, nodal diaphragm absent. Thorns absent. Aerial roots absent. Sap translucent. Resin absent.

BUDS terminal and axillary buds dimorphic. Terminal bud present (floral bud), narrow ovoid, 7.1 mm long, pointed. Axillary buds present (vegetative), 1, ovoid, 0.7-2 mm long, blunt. Bud scales 4-6, dark orange-red or reddish orange to dark reddish orange or orange to dark orange, imbricate, ovate, chartaceous, acute or obtuse, hairs short and unbranched (on floral bud scales), appressed, unicellular, uniseriate, white, dense, throughout, not glabrescent, without glands. Leaf scars obdeltate, 1-1.3 mm high, 1-1.5 mm wide, glabrous. Vascular bundle scars 1, U-shaped, 0.3-0.4 mm tall.

LEAVES alternate, 1 per node, crowded toward stem apex, divergent from stem, simple. Stipules absent. Leaves petiolate, petiole "typical", 0.3-0.5 cm long, hairs short and unbranched or hairs long and unbranched, erect or appressed, unicellular or multicellular, uniseriate or multiseriate, dense, throughout, not glabrescent, without glands. Leaf: abaxial surface light green, adaxial surface green, blades narrowly elliptic or elliptic, plane, symmetric, 3.2-6.8 cm long, 1-2.7 cm wide, chartaceous, base cuneate, margin ciliate or dentate (after cilia fall off), apex mucronate and acute or obtuse, abaxial surface hairs short and unbranched and hairs long and unbranched, appressed (long hairs) or spreading (short hairs), multicellular (long hairs) or unicellular (short hairs), multiseriate (long hairs) or uniseriate (short hairs), white, moderately dense to sparse (or short hairs absent), along midveins (long hairs) or throughout (short hairs), not glabrescent, without glands, adaxial surface hairs short and unbranched and hairs long and unbranched, appressed, unicellular and multicellular, uniseriate and multiseriate, white, moderately dense to sparse (or short hairs rarely absent), throughout, not glabrescent, without glands. Brochidodromous venation, veins 6-9. Leaf lobes absent. Spines absent. Tendrils absent.

INFLORESCENCES monomorphic, regular or, if dimorphic, female inflorescence simple, raceme, terminal. Peduncle absent. Rachis present, 0.2-0.5 cm long, with bracts. Bracts sessile, blades: abaxial surface orange or orange-red or reddish orange, adaxial surface orange or orange-red or reddish orange, oblanceolate or linear, involute, 7.5-10.3 mm long, 0.8-3 mm wide, base attenuate, margin ciliate, apex obtuse, abaxial surface hairs short and unbranched, abaxial hairs appressed, unicellular, uniseriate, white, dense, apically, not glabrescent, without glands, adaxial surface hairs short and unbranched, appressed, unicellular, uniseriate, white, dense, apically, not glabrescent, without glands. Pedicel (5.5-)7-16 mm long, hairs short and unbranched and hairs long and unbranched, hairs erect and appressed, unicellular and multicellular, uniseriate and multiseriate, white and light yellow, moderately dense or dense, throughout, not glabrescent, glands present or without glands, glands at apex of hairs, dark yellow. Bracteoles 2, sessile, at base of pedicel, not connate, bracteoles: abaxial surface reddish orange or light reddish orange, bracteole: adaxial surface reddish orange or light reddish orange, linear, involute, 3.5-4.7 mm long, 0.1-0.3 mm wide, base attenuate, margin laciniate or ciliate, apex acute (lacerate). Cupules absent.

FLOWERS precocious, formed on short shoots, monomorphic, with sepals and petals readily distinguishable from one another, bisexual. Perfect or female flowers light red or white (rare), 5-merous, 30-40 mm long, 25-32 mm wide, 5-10 flowers per inflorescence, fragrance present (spicy), perianth of two whorls. Calyx present, actinomorphic, crateriform, of fused sepals, persistent, abaxial and adaxial surfaces the same color, dark yellow, 0.4-3 mm long, 1.7-3.9 mm wide, tube 0.3-0.5 mm long, calyx limb 0.1-2.1 mm long, 1.7-3.9 mm wide. Sepals or sepal lobes 5, widely ovate or very widely ovate or widely depressed ovate, 0.3-1.2 mm long, 0.4-1 mm wide, base truncate, margin ciliate (with or without glands), apex acute or obtuse, abaxial surface hairs short and unbranched and hairs long and unbranched, erect and appressed, unicellular and multicellular, uniseriate and multiseriate, white and light yellow, moderately dense or dense, throughout, not glabrescent, glands present or without glands, glands at apex of hairs, dark orange, adaxial surface glabrous, without glands. Epicalyx absent. Corolla present, zygomorphic, infundibuliform, of fused petals, deciduous, abaxial and adaxial surfaces the same color, light red or white (rarely), 30-40 mm long, 25-32 mm wide, corolla limb 10-12 mm long, 25-32 mm wide. Petals or petal lobes 5, "normal", lanceolate or narrow oblong, 15-17 mm long, 6 mm wide, base attenuate or truncate, margin entire, apex obtuse, abaxial surface hairs short and unbranched and hairs long and unbranched, erect and appressed, unicellular and multicellular, uniseriate and multiseriate, white or light yellow, moderately dense, throughout, not glabrescent, glands present or without glands, glands at apex of hairs, light yellow, adaxial surface hairs short and unbranched and hairs long and unbranched, appressed, unicellular and multicellular, uniseriate and multiseriate, white, sparse, not glabrescent, glands present or without glands, glands at apex of hairs, white. Gynoecium syncarpous. Carpels 5. Stigmas 1, capitate. Styles persistent, 1, 42-47 mm long. Ovary superior, 1.9-2.2 mm long, 1.1-1.4 mm wide, nectiferous disk present. Locules 5. Placentation apical axile. Androecium alternate. Stamens 5, 34-42 mm long. Anthers oblong, opening by pores, opening 1/4 of entire anther, bithecal, orange or light orange or light orange-yellow, glabrous. Filaments free, straight, white, hairs short and unbranched, erect, unicellular, uniseriate. Staminodes absent.

FRUITS septicidal capsule, dark orange-red, narrowly lanceoloid, 12-23 mm long, 2-5 mm wide, hairs short and unbranched and hairs long and unbranched, appressed or spreading, unicellular and multicellular, uniseriate and multiseriate, white or light yellow, sparse, throughout, glabrescent, glands present (also nonglandular hairs present), glands at apex of hairs, dark yellow.

SEEDS many, light orange, oblong, oval or circular, 1.8-3.9 mm long, 0.5-0.9 mm wide, winged, not tailed, lineate.

Habitat

Dry areas (rocky woods and rich woods).

Rarity Status

Heritage global rank -- G5

Connecticut -- Not listed

New Jersey -- (Heritage rank: S3)

New York -- Not listed

Species Biology

Flowering

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

Pollination

(Olszowy, 1977)

Mellitochory -- Apis mellifera L.

Fruiting

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

Dispersal

Unknown.

Germination

Unknown.