Carmel Browne presented the Species Talk on 16 March 2013.
The area of distribution of this species extends from northern Burma to the Chinese province of Yunnan in moist, upland forests.
B. hemsleyana was introduced to Kew Gardens by way of seed collected in south Yunnan in 1899. It was named in honour of William Hemsley who worked on Chinese plants at Kew at that time.
B. hemsleyana is rhizomatous, jointed at or below the soil with erect stems. The leaf blade is palmately compound, glossy green, sparsely hairy between the veins, paler green beneath with a reddish tinge. The petioles are pink with short, woolly hairs. Flowers are pink and fragrant.
I chose to speak on this species today because this is only the second time it has flowered for me. It has been described as difficult. From my experiences, I have found it requires a cool, moist, well lit situation with good air movement. Because it naturally produces short, closely spaced stems, good air circulation is essential to keep fungal diseases at bay. A well-drained premium mix that is allowed to dry between waterings suits B. hemsleyana.
B. hemsleyana, B. rex, B. pedatifida and B. circumlobata are closely related and all belong to section Platycentrum. B. hemsleyana has been successfully crossed with Rex Cultorum begonias. B. ‘Raspberry Swirl’, B. ‘Picasso’ and B. ‘Hula Skirt’ are the results of such crossings. I do not know if these have ever been grown in Australia.