1Corolla tube inflated near insertion of stamens, corolla lobes recurved; flowers cream to white
1'Corolla tube not inflated (but see also under V. rosea), corolla lobes patent or ascending; flowers white or differently coloured
2Flowers blue, nodding; roots tuberous, forming dense clumps and oriented like the rays of a star
2'Flowers if blue never nodding; root system differently shaped (but compare V. flavescens)
3Stems purple to red; corolla lobes acuminate to caudate, purple to blue
3'Stems differently coloured; corolla lobes acute to obtuse, rarely acuminate (V. acuminata), rarely purple to blue (V. caerulea)
4Calyx tube often split for most of its length along 1 or 2 sides; corolla blue to purplish (often fading to white)
4'Calyx not split, entire, 5-lobed; corolla not blue
5Flowers < 25 mm long
5'Flowers > 25 mm long
6Flowers solitary; corolla yellow (rarely white to flesh-coloured)
6'Inflorescence several-flowered; corolla white, yellow, or orange
7Thecae with a basal, tail-like, densely hairy appendage; flowers often 4-merous
7'Thecae without a basal, tail-like, densely hairy appendage; flowers always 5-merous
8Corolla white to pale pink; calyx 2.5-6 mm long
8'Corolla yellow to orange; calyx 5-9 mm long
9Corolla yellow; seeds filiform
9'Corolla differently coloured; seeds globose
10Calyx 30-40 mm long; corolla lobes ascending, white, mauve, or pink
10'Calyx 6-15 mm long; corolla lobes patent, white, pink, or red
11Calyx 12-15 mm long; corolla lobes white, acuminate
11'Calyx 6-12 mm long; corolla lobes pink to red, obtuse