Species Key:
The cultivated species of the genus Buddleja

I wrote this key for the Trees and Shrubs Online Buddleja Page, sponsored by the John Spedan Lewis Foundation, and it is reproduced here with their permission. Only the species hardy or almost hardy in the UK are included, and the tender species excluded. Most species have pop-up images.



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1a Leaves alternate. Buddleja alternifolia
1b Leaves opposite. 2
2a Leaves very narrowly oblong, 10X or more as long as wide, corolla white, disc-shaped, 12-15m diameter. B. virgata
2b Leaves ovate, lanceolate, elliptic or somewhat triangular. 3
3a Flowers yellow or orange, arranged in tight spherical heads. 4
3b Flowers not arranged in spherical heads. 7
4a Leaves small, densely tomentose on both surfaces, ovate with crenate margin; inflorescence a terminal spherical head of brownish orange flowers subtended by pair of leafy bracts. B. marrubiifolia
4b Leaves large, lanceolate, inflorescence composed of 3-7 spherical heads. 5
5a Leaves subcoriaceous, upper surface glabrous, undersides conspicuously white tomentose, flowers burnt orange. B. megalocephala
5b Leaf upper surface somewhat rugose, flowers yellow or orange. 6
6a Leaves large, lanceolate, upper surface rugose. Inflorescence a false raceme of 5-7 spherical heads, flowers yellow to orange. B. globosa
6b Underside of leaves, branchlet and buds more tomentose than in (4a) B. globosa, leaves also narrower and connate at base, flowers bright orange. B. araucana
7a Stamens exserted from corolla tube on filaments. 8
7b Stamens held in throat or within corolla tube, sessile or with only very short filaments. 13
8a Stamens fully exserted on long filaments. 9
8b Stamens slightly exserted on short filaments. 10
9a Corolla yellow, stamens also yellow, well exserted from throat. Leaves glaucous, triangular-ovate, irregularly dentate to crenate. B. glomerata
9b Corolla white, stamens well exserted from throat. Leaves narrow, willow-like. B. saligna
10a Leaf blade narrowly elliptic, upper surface bullate; inflorescence congested, corolla white with a wide golden-orange throat; stamens slightly exserted. B. loricata
10b Leaves ovate, cordate or elliptic, sinuate-lobed, petiolate, rugose and bullate above; flowers sessile, in glomerules. Corolla white, greenish or yellow-orange, corolla tube very short, 1.5-2.5mm long; stamens slightly exserted. 11
11a Flowers white, greenish white or cream, indument on lower surface appressed. B. cordata subsp. tomentella
11b Flowers yellow-orange. 12
12a Flowers yellow-orange, indument on lower leaf surface usually thick and floccose, sometimes appressed. Inflorescences as long or longer than average leaves B. cordata subsp. cordata
12b As (12b) B. cordata subsp. cordata, but inflorescences half the length of average leaves. B. cordata subsp. ovandensis
13a Corolla tube with significant curvature, 10-20mm long 14
13b Corolla tube straight. 16
14a Branchlets terete, pubescent to tomentose. Leaves ovate, margin sub-entire, tomentose above, densely tomentose beneath. Inflorescence usually a horizontal panicle. Corolla purple to mauve-blue. B. curviflora
14b Branchlets quadrangular, less conspicuously pubescent. 15
15a Branchlets quadrangular to sub-quadrangular, sometimes narrowly winged. Leaves ovate-acuminate, glabrous and sometimes glossy above, rusty pubescent beneath; inflorescences pendulous panicles, corolla purple. B. lindleyana
15b Branchlets quadrangular and widely four-winged. Leaves narrowly elliptic, acuminate at the apex, margin repand-dentate to subentire, glabrous above, sparsely pubescent to almost glabrous beneath. Inflorescence more upright on opening than in (15a) B. lindleyana. Corolla lavender or violet. B. japonica
16a Leaves large, elliptic and acuminate. Inflorescence lax; large corolla pink or wine-red, 1.5-2.5cm diameter, 20-30mm long, 6-9mm wide at throat, stamens and stigma in throat. B. colvilei
16b Corolla 1cm or less in diameter, opening at throat 5mm or less. 17
17a Corolla orange, tube cylindrical, 28-48mm long, stamens in throat, leaves sub-coriaceous, elliptic to lanceolate. 18
17b Corolla tube less than 20mm long. 19
18a Corolla tube 28-34mm long, calyx lobes acute. B. speciosissima
18b Corolla tube 39-48mm long, calyx lobes acuminate. B. longiflora
19a Corolla small, lobes erect, corolla generally less than 6mm diameter. 20
19b Corolla diameter generally greater than 6mm. 23
20a Leaves elliptic to ovate, acuminate at apex, upper surface dark green and glossy, underside whitish. Inflorescence many flowered panicle, flowers sweetly scented, corolla white or cream with orange throat, lobes small less than 2.0 x 2.0 mm, tube 5.5-9.0 mm long, 1.2-2mm dimeter; anthers inserted well above the middle of the corolla tube. B. auriculata
20b Leaves not glossy or shiny on upper surface. 21
21a Leaf blades narrowly elliptic, apex acuminate, undersides stellate-tomentose. Inflorescence terminal and spiciform; corolla small, mostly white without a conspicuous yellow throat, lobes erect, corolla tube 2.5-4.8 mm long and mostly less than 1mm diameter; stamens inserted above middle of corolla tube. B. asiatica
21b Inflorescence long and narrow thyrsoid cyme. Corolla pale lilac, mauve or pink, usually with a yellow throat. Stamens inserted in or near the mouth. 22
22a Leaf upper surface glabrous, mid-green, underside only minutely stellate-tomentose. Branchlets rounded terete. Inflorescence terminal, narrow and cylindrical thyrsoid cyme. corolla small, pale lilac or pink, corolla tube 4-6.5 mm long, widening slightly towards the mouth, exterior glabrous or glabrescent, stamens inserted at or just below the mouth. B. albiflora
22b Leaf upper surface with some stellate hairs, lower surface tomentose. Branchlets four-angled and narrowly winged. Inflorescence cylindrical, thyrsoid cyme. Corolla small, usually less than 6mm diameter. white, lilac or purple, corolla tube 4-6 mm long, exterior tomentose, stamens inserted somewhat below the mouth. B. myriantha
23a Leaf blade triangular to somewhat ovate, margins crenate, dentate or shallowly lobed; both surface densely tomentose, upper surface occasionally glabrescent. Corolla pale lilac, pink or violet, exterior tomentose. 24
23b Leaves ovate or elliptic. 25
24a Leaves generally more than 6cm in length. Inflorescence spicate or paniculate cymes. Pistil length more than 4mm on average. B. crispa
24b More compact growth habit than in (24a) B. cripsa. Leaves small, generally less than 5cm in length. Inflorescences a terminal thyrse, few flowered. Pistil length less than 4mm on average. B. caryopteridifolia
25a Leaves sage-like, connate or with leafy stipules, upper surface rugose and bullate, underside tomentose with very prominent venation; inflorescence paniculate, flowers sweetly scented, corolla blue, lilac or white, tube 4-7mm long, anthers on short filaments inserted approximately in middle of the tube. B. salviifolia
25b Leaves petiolate and not sage-like. 26
26a Corolla diameter roughly 7 - 10mm. Diameter of corolla tube 3.0 mm or more. Leaf blades narrowly ovate, apex acuminate, branchlets four-angled, often winged. 27
26b Diameter of corolla tube narrow, 3 mm or less. 28
27a Calyx, exterior of corolla tube and ovary glabrous, or ovary sparsely tomentose towards upper half. Corolla white, pink or purple. Corolla tube sometimes widening towards the mouth, 5-8mm long, only slightly longer than pistil, stamens at mouth and level or almost with stigma. B. forrestii
27b Calyx, exterior of corolla tube and ovary tomentose to densely tomentose. Corolla white, pink, maroon or purple. Corolla tube cylindrical, much longer than pistil, stamens at mouth and placed significantly above the stigma. B. macrostachya
28a Leaf blade narrowly ovate to elliptic, upper surface with spreading hairs; margin serrate to crenate, apex acuminate. Indumentum on underside of leaves, on branchlets and flower parts very densely tomentose to floccose, hairs long and often individually visible. Inflorescences terminal spicate or thyrsoid cymes, almost cylindrical. Corolla purple, tube 5-6 mm long, 2-3 mm wide, stamens inserted at mouth. B. nivea
28b Leaves and branchlets tomentose (but less so than in (28a) B. nivea, tomentulose or glabrescent. 29
29a Leaf blade narrowly ovate to elliptic. Inflorescence spicate, long-conical in shape, many flowered and showy. Corolla white, lilac, blue or purple. Corolla tube 8-13 mm long, less than 2mm in diameter. Flowering from mid-summer. 30
29b Leaf blade elliptic or ovate. Inflorescence paniculate or thyrsoid cyme, corolla white, pink or lavender. Flowering in the early spring. 31
30a Both surfaces of leaf and petiole densely tomentose. Branchlets terete, stellate tomentose, exterior of corolla tube tomentose, stamens inserted in upper third. B. fallowiana
30b All parts less densely tomentose than in (20a) B. fallowiana. Upper surface of leaf blade sub-glabrous, branchlets four-angled. Exterior of corolla tube pubescent, not conspicuously tomentose, stamens inserted at middle or towards the base. B. davidii
31a Leaf blade elliptic or narrowly so, up to 16cm in length, acuminate at apex, margin entire, upper surface glabrous, fine off-white to tan indumentum below. Inflorescence paniculate, lax, axillary or terminal; corolla rose-pink or lavender, tube 11-16mm long, 1.5-2 mm diameter, exterior sparsely to densely tomentose, interior with few glandular hairs, stamens inserted slightly above middle of the tube. B. delavayi
31b Underside of leaves, petioles, branchlets and inflorescences densely stellate-tomentose, but never floccose as in (28a) B. nivea. Leaf blade narrowly ovate or elliptic, up to 25cm in length. Inflorescence thyrsoid or paniculate. 32
32a Leaf blade elliptic to ovate, upper surface glabrescent, underside densely tomentose. Corolla white, pale lavender or lilac-pink, corolla tube 8-10 mm long and 1.6-2.2 mm diameter Stamens inserted approximately at one third of the tube length from the mouth of the corolla tube. B. officinalis
32b Leaf blade narrowly ovate or elliptic, margin sometimes lobed, upper surface slightly bullate and stellate tomentulose, lower surface densely tomentose. Corolla white, pink or lavender, corolla tube 6-10 mm long, 1.2-1.6 mm diameter. Stamens inserted towards the mouth of the corolla tube. B. paniculata



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