| 1 | Plants erect | 2 |
| 1 | Plants climbing or trailing | 6 |
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| 2 | Leaves markedly rough to the touch; flowers cream to yellow | Thunbergia huillensis |
| 2 | Leaves smooth or very slightly rough to the touch; flowers various colours | 3 |
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| 3 | Leaves irregularly serrate with long (> 5 cm) petioles; flowers usually white, less often blue; E only | Thunbergia petersiana |
| 3 | Leaves very shortly stalked or sessile | 4 |
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| 4 | Small (c. 35 cm) annual herb, rare, recorded from W Zimbabwe; flower colour unknown | Thunbergia annua |
| 4 | Plant not a small annual herb | 5 |
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| 5 | Leaves lanceolate to narrowly elliptic; widespread distribution | Thunbergia oblongifolia |
| 5 | Leaves ovate; confined to E only | Thunbergia natalensis |
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| 6 | Flowers blue | Thunbergia crispa |
| 6 | Flowers white, cream, yellow or orange | 7 |
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| 7 | Petioles strongly winged | 8 |
| 7 | Petioles not or only slightly winged | 9 |
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| 8 | Flowers with a dark "eye"; most common in division E, scarce elsewhere | Thunbergia alata |
| 8 | Flowers without a dark "eye"; recorded only from divisions N and W | Thunbergia reticulata |
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| 9 | Leaves markedly rough to the touch | Thunbergia dregeana |
| 9 | Leaves smooth or very slightly rough to the touch | Thunbergia subalata |
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