Key to Penstemon (taller cultivars) in the RHS trial
When using this key it should be noted that colours and markings on flowers and stems may change as the season progresses. Cultural conditions may also affect size and colour. Note that, since the trial on which this key is based, several new cultivars have been introduced.
| 1a | Flowers white, sometimes very faintly tinged pink especially in bud; corolla tube less than 3 times as long as wide |
'White Bedder' (syn. 'Snow Storm'; 'Royal White') |
|---|---|---|
| b | Flowers creamy white; corolla tube 3 times as long as wide | P.hartwegii 'Albus' |
| c | Flowers not white, or if white also with consistent pink colouring | 2 |
| 2a | Flower stems arising from rosette of leaves; lower 3 corolla lobes strongly reflexed against corolla tube. | 'Prairie Fire' |
| b | Plant not as above | 3 |
| 3a | Flower mouth round; flower almost regular in shape; very large, over 4 cm across | 4 |
| b | Flower mouth flattened at top; flower irregular in shape; 4 cm or less across | 5 |
| 4a | Flowers red with white throat | 'Rubicundus' |
| b | Flowers pink and white with white throat | 'Osprey' |
| c | Flowers purplish red with white throat | 'Maurice Gibbs' |
| 5a | Plant low growing, often somewhat spreading, not exceeding 50cm when in flower. | 6 |
| b | Plant upright, exceeding 50cm when in flower | 8 |
| 6a | Flowers more or less rounded, pale purple | 'Papal Purple' |
| b | Flowers not rounded, blue to reddish purple | 7 |
| 7a | Leaves dull, bluish green; stem reddish upright flower | 'Catherine de la Mare' |
| b | Leaf shiny, mid-green; stem pale brown red, spreading to ascending; flower pale blue to mauve | 'Margery Fish' |
| c | Leaf shiny, mid green; stems reddish upright; flowers mid blue mauve |
'Sylvia Buss' (See note 1) |
| 8a | Corolla tube less than 3 times as long as wide | 9 |
| b | Corolla tube at least 3 times as long as wide | 38 |
| 9a | Plants usually under 60 cm; leaves under 1cm wide; corolla tube less than 1 cm wide | 37 |
| b | Plants usually over 60 cm; leaves broader; corolla tube over 1cm wide | 10 |
| 10a | Flowers without marks or stripes in white throat | 11 |
| b | Flowers with marks and/or stripes in white throat | 16 |
| 11a | Flowers purple | 12 |
| b | Flowers not purple | 13 |
| 12a | Flowers pale mauve | 'Alice Hindley' |
| b | Flowers deep purple | 'Countess of Dalkeith' |
| 13a | Flowers pink with white throat | 14 |
| b | Flowers pink and white with white throat | 15 |
| 14a | Flowers pale pink | 'Sutton's Pink Bedder' |
| b | Flowers deep reddish pink | 'Whitethroat' |
| 15a | Corolla tube narrow; flowers pale pink, under 3.5cm across | 'Thorn' |
| b | Corolla tube broad; flowers pale pink, under 3.5cm across | 'Peace' |
| c | Corolla tube broad; flowers bright pink, over 3.5cm across | 'Beech Park' |
| 16a | Flowers with faint marks or stripes in throat | 17 |
| b | Flowers with heavily striped and marked throats | 21 |
| 17a | Flowers pink | 18 |
| b | Flowers crimson red with reddish marks at mouth only | 'King George V' |
| 18a | Underside of corolla tube paler pink to cream | 19 |
| b | Corolla tube same colour below and above | 20 |
| 19a | Flowers pale dusky pink, about 3cm across | 'Welsh Dawn' |
| b | Flowers bright reddish pink, about 4cm across | 'Flamingo' |
| 20a | Flowers clear pink with a few lines in throat | 'Pennington Gem' |
| b | Flowers bright red pink with faint streaks at mouth; leaf mid green | 'Myddelton Gem' |
| c | Flowers bright red pink with a few distinct lines in throat; leaf dark green | 'Southgate Gem' |
| 21a | Flowers large over 3.5cm wide | 22 |
| b | Flowers smaller, less than 3cm wide | 26 |
| 22a | Flowers purple | 23 |
| b | Flowers red | 24 |
| 23a | Stems green; throat distinctly white with dark stripes; flowers deep purple | 'Raven' |
| b | Stems red to green; flowers red purple; mouth without dark patches | 'Port Wine' |
| c | Stems red purple; flowers red purple; mouth with very dark patches |
'Rich Ruby' (also grown as 'Ruby Fields') |
| 24a | Stems and calyces very dark purplish red | 'Souvenir d'André Torres' |
| b | Stem red but not dark purplish red | 25 |
| 25a | Flowers with definite dark patches at mouth | 'Flame' |
| b | Flowers very bright red with faint dark patches at mouth | 'Chester Scarlet' |
| c | Flowers with no dark patches at mouth | 'Red Emperor' |
| 26a | Flowers pink | 27 |
| b | Flowers not pink | 29 |
| 27a | Flowers bright red pink | 28 |
| b | Flowers rose pink | 'Hidcote Pink' |
| 28a | Stem green; leaves shiny olive green tending to fold upwards | 'Modesty' |
| b | Stem red to brown, leaf grey green, flat | 'Hewell Pink Bedder' |
| 29a | Flowers red | 30 |
| b | Flowers not red | 31 |
| 30a | Flowers bright pinkish red; stems brown red | 'Schoenholzeri' |
| b | Flowers scarlet red; stems very dark red purple | 'Drinkstone' |
| c | Flowers crimson red; stems brown-red | 'Andenken an Friedrich Hahn' (syn. 'Garnet') |
| 31a | Flowers pale purple to blue | 32 |
| b | Flowers deep purple | 33 |
| 32a | Throat heavily marked maroon-red; corolla tube blue at base only; lobes very pale purple | 'Mother of Pearl' |
| b | Throat lined red purple; corolla tube tinged blue, lobes reddish purple | 'Stapleford Gem' |
| 33a | Flower buds arranged in cluster at end of inflorescence; flower purple with blue base to corolla tube; throat white with lines | 'Sour Grapes' |
| b | Flower buds not arranged as above | 34 |
| 34a | Flowers red purple, stems very dark red purple; plant to 90 cm in flower | 35 |
| b | Flowers deep blue purple; plant about 70 cm in flower | 36 |
| 35a | Corolla tube broad less than 2 times as long as wide; throat white with stripes | 'Burgundy' |
| b | Corolla tube narrow, nearly 3 times as long as wide; throat very dark | 'Blackbird' |
| 36a | Leaves mid green; stems purple to green; corolla tube blue at base |
'Midnight'/'Purple Bedder' (See note 2) |
| b | Leaves dark green; stem very dark red purple; corolla tube not distinctly blue at base | 'Russian River' |
| 37a | Flowers pale pink with few throat markings | 'Apple Blossom' |
| b | Flowers pink with striped throat | 'Evelyn' |
| c | Flowers purplish pink | 'Threave Pink' |
| 38a | Leaves clasping stem, shiny; stems hairless | P. hartwegii |
| b | Leaves not clasping stem, not shiny; stems hairy |
39 (See note 3) |
| 39a | Leaves ovate to 5cm long by 2 cm wide; plant to 90cm tall, flower red. | P. isophyllus |
| b | As above, flower rose pink | 'Connie's Pink' |
| c | Leaves to 6cm long by 1.5 cm wide; plant less vigorous | 'Cherry Ripe' |
Notes
1. These three cultivars are very similar and the characters used do not always appear consistent.
2. 'Midnight' and 'Purple Bedder' are very similar but in the trial 'Midnight' appeared to be more floriferous.
3. 'Windsor Red (syn. 'Cottage Garden Red') appears to be very closely related, possibly a selection of the species with more intense red flowers.