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Key to Commelina

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Show caption*© Alaina Krakowiak, some rights reserved (CC BY), uploaded by Alaina Krakowiak 1 Spathes with margins free to the base; [introduced species, usually in weedy habitats].

2 Spathes generally whitish or pale green toward the peduncle, with contrasting dark green veins; middle petal white or paler than the others; capsules with 2 locules (the third aborting); seeds rugose foveate-reticulate  Commelina communis

2 Spathes lacking contrasting veins; middle petal about the same color as the others; capsules with 3 locules; seeds reticulate or smooth to faintly alveolate.

3 Spathes not at all to slightly falcate (the lower margin straight or very nearly so); upper cyme usually vestigial (rarely well-developed and 1-flowered); seeds smooth to faintly alveolate; peduncles of the spathes with hairs to 0.5 mm long  Commelina caroliniana

3 Spathes usually distinctly falcate (the lower margin curved); upper cyme in larger spathes usually well-developed and 1-several-flowered; seeds deeply reticulate; peduncles of the spathes with hairs to 0.1 mm long.

4 Leaf blades 1.5-5 (-8) cm long × 0.5-1 (-2.2) cm wide; capsules usually 5-seeded  Commelina diffusa

4 Leaf blades 6-14 cm long × 1-3.3 cm wide; capsules usually 1-2 seeded  Commelina gigas

Show caption*© Gary P. Fleming 1 Spathes with margins fused basally; [native species, usually in natural habitats, or introduced and weedy].

5 Flowers peach-colored  Commelina gambiae

5 Flowers white and/or bluish.

6 Leaf sheaths not auriculate at the summit, ciliate with coarse reddish-brown, white, or colorless hairs; middle petal blue, lilac, or lavender; [mostly of moist or wet soils].

7 Perennial from horizontal rhizomes, often forming clonal patches of erect stems; leaf blades lance-oblong, 6-20 cm long, the apex acuminate; leaf margin and upper surface scabrous; plants lacking subterranean, cleistogamous flowers; [native, mostly of moist floodplain forests]  Commelina virginica

7 Annual from fibrous roots, the stem decumbent; leaf blades broadly elliptic-ovate, 1-9 cm long, the apex acute to obtuse; leaf margin and upper surface pubescent or glabrous; plants often bearing subterranean, cleistogamous flowers; [exotic, weedy].

8 Capsule usually 5-seeded; sheaths usually with red hairs at summit; stamen filaments not winged  Commelina benghalensis

8 Capsule usually 1-seeded; sheaths with re hairs at summit; stamen filaments winged  Commelina forskaolii

6 Leaf sheaths prolonged upwards into auricles, ciliate with white hairs; middle petal white; plant perennial from thickened, fibrous roots, not forming clonal patches; [mostly of dry, sandy or rocky soil].

9 Larger leaves (6-) 10-15 cm long, (1.1-) 1.5-4.0 cm wide (typically 3-6× as long as wide); spathes (2.0-) 2.5-3.6 cm long  Commelina erecta var. erecta

9 Larger leaves 4-15 cm long, 0.4-1.4 cm wide (typically 5-12× as long as wide); spathes 1-3 cm long.

10 Spathes 1-2.5 cm long, 0.9-1.5 cm high along the adaxial side; leaves 4-10 cm long; [primarily of the Coastal Plain, especially on sandhills and dunes]  Commelina erecta var. angustifolia

10 Spathes 2.5-3.0 cm long, 1.2-1.8 cm high along the adaxial side; leaves 7-15 cm long; [primarily midwestern and western]  Commelina erecta var. deamiana