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Iochroma cyaneum 'Karl Hartweg'

Accepted name

Iochroma cyaneum 'Karl Hartweg'

Synonyms Iochroma cyaneum pale blue form (probably)
Distribution  
Description Habit: shrub to 2 m or more in cultivation.

Leaves: elliptic, basally acuminate, 10 - 23 cm x 5 - 10 cm with a 2 - 9 cm petiole.  Adaxial surface pale green, slightly hairy but more so on midrib; abaxial surface pale green with dense light brown hairs when young becoming sparse with age, veins more or less straight at junction with midrib.

Flowers: blue violet (approximately RHS blue violet N89a when opening under glass, fading to 85a; hardly changed when grown in full sun outdoors).

Calyx: inflated, pale green both under relatively shaded conditions and in full sun.

Corolla: tube 25 - 48 mm long x ca. 8 - 9 mm wide at mouth at anthesis, petals 5.

Gynoecium: stamens 5, exerted, anthers, 3 - 3,5 mm long, yellowish usually tinged bluish before anthesis.

Fruit: ca. 2 cm long x 1.5 cm wide, conical, partly enclosed in calyx, area around stigma tinged purplish when young, colour fading as fruit matures; greenish-yellow when ripe.

References Shaw 1998: 168
Comments Julian Shaw gave the cultivar name 'Karl Hartweg' which has been tentatively accepted by the RHS horticultural database.  This is probably the "pale blue" form of Iochroma cyaneum accepted in the RHS horticultural database although it cannot now be proven.

'Karl Hartweg' has the smallest flowers of the three clones of Iochroma cyaneum available in the UK, usually slightly less than 5 cm long and 1 cm wide at the mouth.  Before opening, the young flowers of 'Karl Hartweg' can seem almost as dark 'John Miers' but quickly fade to pale blue violet.  The calyx is distinctly inflated but to a smaller extent than in 'John Miers'.  Shoot tips of 'Karl Hartweg' are brownish due to hairs on the leaf whereas 'John Miers' is whitish.

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last updated 10/10/2008