The Imperial System and the Tropical Hydrangea

Unexpected connections…

Bronwen Scott
5 min readApr 22


Big cluster of exuberant pink flowers hanging down against a backdrop of a large garden.
Tropical Hydrangea (Dombeya wallichii), Far North Queensland. © Bronwen Scott.

I was about to leave when my friend asked, ‘Have you seen the Tropical Hydrangea?’

I hadn’t. Hydrangeas are staples of older, long-established gardens and they seem to have gone out of fashion, displaced by native species such as Grevillea and Melaleuca. They grow well on the Atherton Tablelands, where the red Pin Gin soils are acid, tinting the flowers mauve to pale blue. I wasn’t familiar with species from the tropics, only the Japanese Hydrangea macrophylla, with its big leaves and ever bigger bunches of flowers.

The Tropical Hydrangea, it turns out, is tropical but is not a hydrangea.

(My war against common names continues.)

Native to eastern Madagascar, the Tropical Hydrangea or, more accurately, Dombeya wallichii, is a garden plant for warmer areas. It belongs to Malvaceae, a family that includes hibiscus, cotton, mallows — and a genus called Bastardia (now sadly synonymised with Abutilon) — but not hydrangeas. Not even close.

Through a series of peculiar events, the Tropical Hydrangea is linked to the USA’s use of Imperial measurements.

Close up of big green leaves.
Leaves of Dombeya wallichii. © Bronwen Scott.

The scientific name honours two men — Joseph Dombey (1742–1794) and Nathaniel Wallich (1786–1854). Both were surgeons and botanists and both were employed by Colonial powers in Asia.

Wallich worked for the Danish Asiatic Company in Serampore in West Bengal. Not long after he arrived in India, hostilities between Denmark and Britain resulted in the town being taken over by the British East India Company. Wallich was imprisoned for a while, but his skills as a doctor saw him quickly released and put to work for the EIC.

While in India, he proposed the establishment of what is now known as the Indian Museum at Kolkata. He was also appointed superintendent of the Kolkata Botanic Garden.

Wallich travelled widely through Asia and to South Africa, and sent out collectors to gather plants on behalf of the EIC. He was a prodigious collector, amassing a huge herbarium, which was…



Bronwen Scott

Zoologist, writer, artist, museum fan, enjoying life in the tropical rainforest of Far North Queensland. She/her. Website: