Flora of North America species comparison

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Commelina

dayflower, widow's-tears
Habit Herbs, perennial or annual.
Roots

thin or tuberous.
Leaves

2-ranked or spirally arranged, not glaucous;

blade sessile or petiolate.
Inflorescences

terminal, leaf-opposed;

cymes 1–2, enclosed in spathes, proximal cyme several-flowered, distal cyme vestigial or with 1–several staminate flowers;

spathes often filled with mucilaginous liquid, margins distinct or basally connate;

bracteoles usually absent.
Flowers

bisexual and staminate, bilaterally symmetric;

pedicels well developed;

sepals distinct or proximal 2 connate, unequal;

petals distinct, proximal petal often different color than distal 2, smaller or subequal, distal 2 blue (occasionally lilac, lavender, yellow, peach, apricot, or white), clawed;

stamens (5–)6, proximal 3 fertile, medial different in form, size from others, distal (2–)3 staminodial;

filaments glabrous;

antherodes commonly 4–6-lobed;

ovary 2–3-locular, ovules 1–2 per locule, 1-seriate.
Capsules

2–3-valved, 2–3-locular.
Seeds

1–2 per locule;

hilum linear;

embryotega lateral.
x

= 11–15.

Commelina
Distribution
map from USDA
Almost worldwide; mainly tropical
[BONAP county map]
Discussion

Species ca. 170 (9 in the flora).

Etymology: for the two Dutch botanists Jan and Kaspar Commelijn, because of the two showy petals

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Parent taxa Commelinaceae
Subordinate taxa
C. benghalensis, C. caroliniana, C. communis, C. dianthifolia, C. diffusa, C. erecta, C. forskaolii, C. gambiae, C. virginica
Key
1. Spathes with margins distinct to base.
→ 2
1. Spathes with margins connate basally.
→ 5
2. Perennials with erect to ascending stems; roots tuberous; leaves linear to linear-lanceolate
C. dianthifolia
2. Annuals or perennials usually with decumbent to scandent stems; leaves narrowly lanceolate to ovate-elliptic.
→ 3
3. Spathes generally whitish or pale green toward peduncle with contrasting, dark green veins; proximal petal white or paler than others; capsules 2-locular; seeds rugose pitted-reticulate
C. communis
3. Spathes without contrasting veins; proximal petal ± concolorous with others; capsules 3-locular; seeds reticulate or smooth to faintly alveolate.
→ 4
4. Spathes not at all to slightly falcate; distal cyme usually vestigial (rarely well developed, 1-flowered); seeds smooth to faintly alveolate
C. caroliniana
4. Spathes usually distinctly falcate; distal cyme in larger spathes usually well developed, 1–several-flowered; seeds reticulate
C. diffusa
5. Flowers apricot- or peach-colored
C. gambiae
5. Flowers blue (rarely lilac to lavender or white).
→ 6
6. Leaf sheaths with auricles at summit; roots stout; proximal petal white, minute; locules all 1-seeded
C. erecta
6. Leaf sheaths not auriculate; roots thin; proximal petal blue to lilac or lavender, conspicuous; some locules usually 2-seeded.
→ 7
7. Perennials with erect to ascending stems; leaf sheaths with red hairs at summit; leaf blades 6–20 cm; spathes 1.5–3.5 cm; subterranean, cleistogamous flowers absent
C. virginica
7. Annuals or perennials with ascending to decumbent, repent or scrambling stems; sheaths with or without red hairs at summit; leaf blades 1.5–7(–9) cm; spathes 0.5–2 cm; subterranean, cleistogamous flowers sometimes present.
→ 8
8. Leaf blades ovate to lanceolate-elliptic; sheaths often with red hairs at summit; lateral stamen filaments not winged; capsules usually 5-seeded
C. benghalensis
8. Leaf blades oblong to lanceolate-oblong or oblong-elliptic; sheaths without red hairs; lateral stamen filaments winged; capsules usually 1-seeded
C. forskaolii
Name authority Plumier ex Linnaeus: Sp. Pl. 1: 40. 1753; Gen. Pl. ed.; 5:25, (1754)
Source FNA vol. 22. Treatment author: Robert B. Faden.
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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