A new nothospecies in Lagerstroemia (Lythraceae) Author Whittemore, Alan T. US National Arboretum, 3501 New York Avenue NE, Washington, DC 20002 - 1958, USA Author Schori, Melanie 0000-0002-2801-635X National Germplasm Resources Laboratory, 10300 Baltimore Avenue, Building 003, Room 124, Beltsville, MD 20705, USA Melanie. Schori @ usda. gov; https: // orcid. org / 0000 - 0002 - 2801 - 635 X chori@usda.gov text Phytotaxa 2022 2022-03-17 539 3 294 300 http://dx.doi.org/10.11646/phytotaxa.539.3.10 journal article 20199 10.11646/phytotaxa.539.3.10 cc5a129f-a9db-4ef9-bebd-ea873722bd17 1179-3163 6364052 Lagerstroemia × egolfii Whittem. & Schori , nothospec. nov. Type :— USA . District of Columbia : North of Conifer Road just west of the old gate, Gotelli Dwarf and Low-Growing Conifer Collection, United States National Arboretum; cultivated tree, accession numbers NA 54979-CH, PI 499825, 10 September 2018 , Whittemore 18-027 ( holotype NA!, isotypes A!, K!, MOR!, TUS!). Figures 1–14 . Diagnosis:— Lagerstroemia × egolfii displays a range of characters that tend to overlap with one or both parents. Leaves are smaller than those of L. fauriei , petals are as large as those of L. indica , and the hypanthium can have 12 weak veins, in contrast to the 12 strong veins of L. fauriei and the 6 veins often seen in L. indica . The full range of intermediate character states is given in Table 1 . Large shrubs or small multitrunked trees to 7 m ; main limbs spreading or upright; bark smooth, shed in thin woody strips, white to bright orange-brown where recently exposed, weathering to light or dark gray or brown. Twigs terete or 4-angled, weakly ridged. Petioles 1–3 mm long; leaf blades obovate or elliptical, 37–75 mm long, (17–) 23–43 mm wide, with (4–)5–8 secondary veins on each side of the midrib; apex rounded, obtuse, or rather short-acuminate. Inflorescences pyramidal, ultimate twigs 4-sided, ± 4-winged, puberulent, sparsely bristly, or glabrous. Hypanthium scarcely veined, or weakly 12-veined, (2–) 3–5 mm long, sepals triangular, 2–4 mm long, acute or acuminate; petals white, pink, red, or purple, claw 5–12 mm long, blade excluding claw 5–11 mm long, 7–10(–14) mm wide. Capsules spherical, 8–12 mm long; seeds with a single wing on one side. The hybrid is named in honor of Donald Roy Egolf (1928–1990), geneticist and prolific plant breeder. Egolf led the program to utilize this hybrid horticulturally and released thirty mildew-resistant cultivars of Lagerstroemia , most of them L. × egolfii . The type was collected from a tree that is an artificial F1 hybrid between L. fauriei and L. indica ( Wang et al. 2011 ) . Clonal material of this plant is sometimes sold in nurseries under the cultivar name ‘Apalachee’ crape-myrtle ( Egolf 1987 ). Material of Lagerstroemia × egolfii in cultivation includes F1, F2, backcross, and various later-generation hybrids. However, since horticulturists value the much larger, often colored petals of L. indica , backcrosses have been made to L. indica but seldom, if ever, to L. fauriei . This range of different genotypes recombines the characteristics of the two parents in many combinations ( Table 1 ). The description above is based on an array of F1 and later-generation hybrids. Lagerstroemia fauriei is usually treated as a distinct species ( Koehne 1907 , Ohwi 1965 , Egolf & Andrick 1978 , Xu et al. 2017 , National Gardening Association 2018 ). However, some recent authors have treated L. fauriei as a variety of L. subcostata Koehne (1883: 20) , following Yahara et al. (1987) . Yahara et al. published the new combination (1987: 98) but gave no justification for the change in status. They said, “This variety is distinguished from var. subcostata by its larger capsules,” but examination of living plants in the United States , plus herbarium specimens at NA and US , confirm Koehne’s contention that the two differ in characters of the bark, petiole, leaf blade, and seed, as well as the size of the capsule ( Table 2 ). In addition, Xu et al. (2017) compared complete chloroplast genomes from one accession of each taxon and found that they differed at many positions, a level of divergence more suggestive of distinct species. For these reasons, L. fauriei is treated here as a separate species. TABLE 1. Characters of Lagerstroemia fauriei , L. × egolfii , and L. indica .

L. fauriei	L. × egolfii	L. indica
Habit	Upright tree	Large shrub or small tree	Spreading low tree or large shrub
Height (m)	to 14	to 7	to 7
Limbs	upright	spreading or upright	spreading
Bark	bright orange-brown weathering to dull light or dark brown	white to bright orange-brown weathering to light or dark gray or brown	white weathering to light or medium gray or gray-brown
Twigs	terete, with 4 low, narrow, sometimes interrupted ridges	terete or 4-angled, weakly ridged	4-sided, 4-winged
Petiole length (mm)	5–10	1–3	0–2
Blade	elliptical to lance-ovate	obovate or elliptical	elliptical or obovate
Blade length (mm)	72–113	37–75	35–65
Secondary veins (on each side)	7–12	(4–)5–8	3–6
Leaf apex	acuminate	rounded, obtuse, or rather short-acuminate	rounded, obtuse, or bluntly short-acuminate
Inflorescence branches	puberulent, seldom glabrous	puberulent, sparsely bristly, or glabrous	sparsely to moderately bristly
Hypanthium veins	12 strong veins, extending to sinuses and along midlines of sepals	scarcely veined, or weakly 12- veined	6 veins extending to sinuses only, or no strong veins
Hypanthium length (mm)	2–3	(2–)3–5	4.0–5.5
Sepal length (mm)	1.5–2.0	2–4	2–3
Sepal shape	triangular	triangular	broadly triangular
Petal color	white	pale purple to purplish red, red, or white	pale purple to purplish red, red, or white
Petal blade length × width (mm)	2–5 × 2–6	5–11 × 7–10(–14)	5–10 × 7–14
Petal claw length (mm)	2.5–3.5	5–12	5–10
Capsule	ellipsoidal	spherical	spherical or short-ellipsoidal

FIGURES 1–4. Lagerstroemia × egolfii , morphology of NA 54979-CH (‘Apalachee’), from which the type specimen was collected. 1. Habit. 2. Bark. 3. Inflorescence. 4. Flower. FIGURES 5–13. Lagerstroemia × egolfii , variation among genotypes. 5. Habit of NA 58471 (‘Natchez’). 6. Habit of NA 54972 (‘Tonto’). 7. Bark of NA 48471 (‘Tuskegee’). 8. Bark of NA 54973 (‘Wichita’). 9. Flower of NA 38449 (‘Natchez’). 10. Flower of NA 54972 (‘Tonto’). 11–13. Capsules of NA 58471 (‘Natchez’). FIGURE 14. Lagerstroemia × egolfii , Holotype. TABLE 2. Characters of Lagerstroemia fauriei and L. subcostata .

Character	L. fauriei L. subcostata
Limbs	Erect Ascending
Bark	Bright orange-brown weathering to dull light or White weathering to medium gray or gray-brown dark brown
Petiole length (mm)	5–10 2–6
Blade length (mm)	72–113 20–68
Secondary veins (on each side)	7–12 3–6
Blade apex	acuminate short-acuminate or bluntly acute
Capsule length (mm)	8–10 6–8
Seed length (mm)	8 4
Seed wing	longer than seed body shorter than seed body

The name Lagerstroemia × egolfii will not apply to all of the mildew-resistant hybrid crape-myrtles, since some are hybrids involving L. limii Merrill (1925: 165) , L. speciosa (Linnaeus in Münchhausen 1770: 357 ) Persoon (1806: 72) , or L. subcostata as well as L. indica and often L. fauriei ( Wang et al. 2011 ) . If a name of general horticultural utility encompassing all of these plants is desired, it would be best to establish a cultivar Group under the International Code of Nomenclature for Cultivated Plants ( Brickell et al. 2016 ).