Chromolaena congesta (Hooker & Arnott) King & Robinson, 1970

Christ, Anderson Luiz, Nakajima, Jimi Naoki & Ritter, Mara Rejane, 2025, Towards a better understanding of the Chromolaena congesta complex (Asteraceae, Eupatorieae): updated synopsis with taxonomic novelties, Phytotaxa 689 (2), pp. 163-184 : 165-166

“ Chromolaena congesta complex”

Subshrubs; xylopodium present; stems erect or decumbent; leaves opposite or alternate, 3–5-veined, membranaceous to coriaceous, abaxial surface usually glandular (sometimes eglandular); secondary capitulescence corymbose or anthelate; primary capitulescence glomerate or corymbose; capitula sessile to pedunculate; phyllaries erect to squarrose, glabrous to tomentose, usually glandular (rarely eglandular); florets 4–30; cypselae glandular or not, glabrous to setulliferous.

Key to the species of the Chromolaena congesta complex

1. Outer and inner phyllaries always attenuate, vinaceous on apex and abaxial surface ................................................ C. gentianoides

- Outer or inner phyllaries acute, acuminate, apiculate, attenuate, cuneate or truncate (never both outer and inner phyllaries attenuate), usually vinaceous or griseous on apex and citrine on abaxial surface (never all phyllaries completely vinaceous) .........................2

2. Abaxial surface of the leaves eglandular............................................................................................................................................3

- Abaxial surface of the leaves glandular..............................................................................................................................................4

3. Leaves orbicular to ovate, rarely lanceolate ............................................................................................................ C. latisquamulosa

- Leaves elliptic to oblanceolate ................................................................................................................................... C. rhinanthacea

4. Leaves alternate on the upper half of the stem ..................................................................................................................... C. hirsuta

- Leaves opposite on the upper half of the stem ...................................................................................................................................5

5. Outer phyllaries squarrose............................................................................................................................................ C. squarrulosa

- Outer phyllaries erect to recurved ......................................................................................................................................................6

6. Stems hirsute to villose.......................................................................................................................................................................7

- Stems glabrescent, strigose, puberulous, sericeous or tomentose ....................................................................................................11

7. Cypselae glandular .............................................................................................................................................................................8

- Cypselae eglandular............................................................................................................................................................................9

8. Leaves typically as long as wide, strigose on the adaxial surface, apices usually obtuse to rounded; outer phyllaries less than 2 mm long.; cypselae usually less than 2.5 mm long .................................................................................................................. C. congesta

- Leaves typically twice as long as wide, hirsute on the adaxial surface, apices usually acute to attenuate; outer phyllaries more than 2 mm long; cypselae usually more than 3 mm long............................................................................................................. C. hirsuta

9. Capitula with 4–5 florets .......................................................................................................................................... C. caaguazuensis

- Capitula with more than 8 florets .....................................................................................................................................................10

10. Leaves twice as long as wide; secondary capitulescences usually anthelate; capitula with 8–13 florets; pappus bristles more than 4 mm long.............................................................................................................................................................................. C. nervosa

- Leaves as long as wide; secondary capitulescences corymbose; capitula with more than 13 florets; pappus bristles less than 4 mm long.................................................................................................................................................................................. C. ascendens

11. Stems sericeous ................................................................................................................................................................................12

- Stems glabrescent, strigose, puberulous or tomentose .....................................................................................................................13

12. Abaxial surface of the leaves lanate; outer phyllaries apiculate, mostly erect (rarely recurved); cypselae glandular......................... ....................................................................................................................................................................................... C. diversifolia

- Abaxial surface of the leaves strigose or sericeous; outer phyllaries usually cuneate, sometimes acuminate, mostly recurved (rarely erect); cypselae typically eglandular ............................................................................................................................ C. squarrulosa

13. Capitula with 4–5 florets .......................................................................................................................................... C. caaguazuensis

- Capitula with more than 6 florets .....................................................................................................................................................14

14. Cypselae eglandular (rarely single glandular hairs in C. squarrulosa ) ............................................................................................ 15

- Cypselae glandular ...........................................................................................................................................................................17

15. Secondary capitulescences corymbose; outer phyllaries eglandular....................................................................... C. latisquamulosa

- Secondary capitulescences anthelate; outer phyllaries glandular.....................................................................................................16

16. Stems usually puberulous; leaf bases truncate, cordate or cuneate; venation emergent on the abaxial surface of the leaves ............. ............................................................................................................................................................................................ C. nervosa

- Stems glabrescent to strigose; leaf bases rounded; venation immersed on the abaxial surface of the leaves.............. C. squarrulosa

17. Plants usually erect; leaves as long as wide, typically deltate with truncate to rounded bases; outer phyllaries usually apiculate, shorter than 2.5 mm long................................................................................................................................................... C. congesta

- Plants usually decumbent; leaves twice as long as wide, typically elliptic or lanceolate with acute to cuneate bases; outer phyllaries usually cuneate, longer than 2.5 mm long.......................................................................................................................... C. elliptica