Flora of North America species comparison

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Hydrangeaceae

Deutzia

hydrangea family, mock-orange family

pride-of-rochester
Habit Subshrubs, shrubs, trees, or vines [herbs], evergreen or deciduous. Shrubs.
Stems

erect to spreading.
Bark

exfoliating in grayish, brownish, or reddish sheets or flakes.
Branches

erect, ascending, spreading, or arching;

twigs with stellate and simple trichomes.
Leaves

usually opposite, sometimes whorled [alternate], simple;

stipules absent;

petiole present or absent;

blade sometimes palmately lobed, margins entire, serrate, serrulate, dentate, denticulate, or crenate;

venation pinnate or acrodromous (Fendlera, Fendlerella, Philadelphus, Whipplea).

deciduous or semideciduous, opposite;

petiole present;

blade lanceolate, elliptic, or ovate, herbaceous, margins serrulate to crenate-denticulate, plane;

venation pinnate.
Inflorescences

terminal or axillary, cymes, panicles, racemes, or corymbs, or flowers solitary.

terminal, corymbose cymes, panicles, or racemes, usually (2–)5–60-flowered, rarely flowers solitary;

peduncle present or absent.
Pedicels

present.
Flowers

bisexual [unisexual], or sometimes marginal ones sterile, radially symmetric (bisexual ones) or bilaterally symmetric with enlarged petaloid sepals (sterile ones);

perianth and androecium nearly hypogynous, perigynous, or epigynous;

hypanthium completely adnate to ovary or adnate to ovary proximally, free distally;

sepals 4–12, distinct or connate basally;

petals 4–12, connate basally [entirely, then calyptrate];

nectary usually present, rarely absent;

stamens 8–200, usually distinct, sometimes connate proximally, free;

anthers dehiscing by longitudinal slits;

pistil 1, 2–12-carpellate, ovary less than 1/2 inferior, 1/2 inferior, or completely inferior, 1–12-locular, placentation usually axile proximally, parietal distally, rarely strictly axile or parietal;

ovules 1–50 per locule, anatropous;

styles 1–12, distinct or connate proximally to most of length;

stigmas (1–)2–12.

bisexual;

perianth and androecium epigynous;

hypanthium completely adnate to ovary, campanulate or ovoid, not ribbed in fruit;

sepals deciduous, 5, erect, triangular to broadly ovate, glabrous or abaxially short-hairy or stellate-pubescent;

petals 5 [10 in some cultivars], valvate or imbricate, spreading, white, pink, or purplish, elliptic to oblong, base clawed, surfaces glabrous or hairy;

stamens 10, in 2 whorls;

filaments distinct, dorsiventrally flattened or terete, gradually or abruptly tapered medially or filiform, apex 2-lobed or not lobed;

anthers globose;

pistil 3–5-carpellate, ovary completely inferior, 3–5-locular;

placentation usually axile proximally and parietal distally, sometimes strictly parietal;

styles persistent, 3(–4), distinct.
Fruits

capsules [berries], dehiscence septicidal, loculicidal, interstylar, or intercostal.

Capsules

hemispheric, cartilaginous, dehiscence acropetally septicidal along septum at base of fruit and also apically.
Seeds

1–50 per locule, funicular appendage present (Fendlerella, Whipplea) or absent.

10–20 per locule, dark brown, ellipsoid.
x

= 13.

Hydrangeaceae

Deutzia
Distribution
North America; Mexico; Central America; South America; Eurasia; Pacific Islands
[BONAP county map]
from USDA
Mexico; Asia (China, Himalaya, Japan, Korea); Pacific Islands (Philippines) [Introduced in North America]
[BONAP county map]
Discussion

Genera 17, species ca. 240 (9 genera, 25 species in the flora).

A. Cronquist (1981) placed Hydrangeaceae among a group of woody families traditionally allied with Saxifragaceae. Phylogenetic studies consistently place Hydrangeaceae in the Cornales and sister to Loasaceae (A. L. Hempel et al. 1995; D. E. Soltis et al. 1995; L. Hufford et al. 2001; Hufford 2004). Within Hydrangeaceae, the western North American genera Fendlera and Jamesia form a clade (subfam. Jamesioideae L. Hufford) that is sister to the rest of the family (subfam. Hydrangeoideae Burnett) (Hufford et al.; Hufford). Subfamily Hydrangeoideae comprises two tribes: Philadelpheae de Candolle ex Duby and Hydrangeeae de Candolle. North American genera in the former are Carpenteria, Deutzia, Fendlerella, Philadelphus, and Whipplea. A molecular phylogenetic study by Y. De Smet et al. (2015) clarified relationships within Hydrangeeae, found Hydrangea to be polyphyletic, and promoted adoption of a broader concept of Hydrangea that includes the eight other genera in the tribe. The two North American genera in the tribe, Decumaria and Hydrangea, are circumscribed here in their traditional senses.

The Hydrangeaceae are well represented in the paleobotanical record dating back to the Upper Cretaceous but best represented in the Tertiary (L. Hufford 2004). Some genera are sources of popular introduced or native ornamentals, including Carpenteria, Deutzia, Hydrangea, and Philadelphus. Some ornamentals have become established outside of cultivation in the flora area. A few North American Hydrangeaceae have reputed medicinal (D. E. Moerman 1998) or toxicologic (G. E. Burrows and R. J. Tyrl 2001) properties.

Trichomes in most Hydrangeaceae consist of a long, unicellular portion, often borne on a multicellular base. The unicellular portion often bears tubercles on its surface. Sometimes instead of tubercles, it bears long extensions, making the trichome appear branched or dendritic. Such trichomes are here referred to as branched.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species ca. 60 (3 in the flora).

A. J. Rehder (1940) recognized 23 species (including eight named hybrids), 27 varieties, and about 27 cultivars of Deutzia growing mostly at the Arnold Arboretum. L. H. Bailey et al. (1976) listed taxa only in the horticultural trade and cited 34 species and 36 cultivars that had been listed in the previous two decades. M. A. Dirr (1998) reported that Deutzia has lost favor as an ornamental over the years. He noted that identification of species, particularly cultivars, borders on the impossible, and nothing is clear-cut in the world of Deutzia identification. He listed seven species and 22 cultivars, including nine cultivars of D. scabra.

In cultivation, deutzias may spread by suckers; several species have escaped and become marginally naturalized. M. L. Fernald (1950) reported that Deutzia gracilis and D. scabra were beginning to spread to thickets and roadsides; there is no evidence that either species has become widely naturalized. H. A. Gleason and A. Cronquist (1991) noted that D. scabra rarely escapes from cultivation.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Woody vines.
Decumaria
1. Subshrubs, shrubs, or trees.
→ 2
2. Twigs with stellate and simple trichomes.
Deutzia
2. Twigs glabrous or with simple or, sometimes, branched trichomes, never with stellate trichomes.
→ 3
3. Flowers both sterile and bisexual.
Hydrangea
3. Flowers all bisexual.
→ 4
4. Stamens (11–)13–90 or 150–200.
→ 5
5. Sepals 4; petals 4 (or 8+ in some horticultural forms); ovaries inferior to 1/2 inferior, 4-locular; styles 1 or 4; leaves deciduous; stamens (11–)13–90.
Philadelphus
5. Sepals 5–7; petals 5–7(–8); ovaries nearly superior, 5–7-locular; styles 1; leaves persistent; stamens 150–200.
Carpenteria
4. Stamens 8–12.
→ 6
6. Stems prostrate to decumbent.
Whipplea
6. Stems erect, ascending, or spreading.
→ 7
7. Filament apices 2-lobed, lobes prolonged beyond anthers; seeds (1–)2–4(–6) per locule.
Fendlera
7. Filament apices not 2-lobed; seeds 1 or 10–50 per locule.
→ 8
8. Inflorescences 100–1000-flowered; capsule dehiscence interstylar, creating pore at base of styles.
Hydrangea
8. Inflorescences 1–35-flowered; capsule dehiscence septicidal.
→ 9
9. Leaf blade margins usually crenate to dentate, rarely entire; blades ovate or broadly ovate to obovate, rhombic, or suborbiculate, venation pinnate; seeds 25–50 per locule.
Jamesia
9. Leaf blade margins entire; blades elliptic to lanceolate, oblanceolate, obovate, or linear-oblong, venation acrodromous; seeds 1 per locule.
Fendlerella
1. Inflorescences corymbose cymes; petals broadly ovate or suborbiculate, imbricate; filaments terete, filiform.
D. parviflora
1. Inflorescences usually racemes or panicles, sometimes flowers solitary (D. gracilis); petals narrowly elliptic to oblong or oblong-lanceolate, valvate; filaments dorsiventrally flattened, narrowly oblong or subulate.
→ 2
2. Leaf blade abaxial surfaces glabrous or glabrate; inflorescences glabrous.
D. gracilis
2. Leaf blade abaxial surfaces densely stellate-pubescent; inflorescences stellate-pubescent.
D. scabra
Source FNA vol. 12, p. 462. Treatment author: Craig C. Freeman. FNA vol. 12, p. 471. Treatment author: Ronald L. McGregor†.
Parent taxa Hydrangeaceae
Subordinate taxa
Carpenteria, Decumaria, Deutzia, Fendlera, Fendlerella, Hydrangea, Jamesia, Philadelphus, Whipplea
D. gracilis, D. parviflora, D. scabra
Name authority Dumortier Thunberg: Nov. Gen. Pl., 19. (1781)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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