Royal Botanical Garden, Calcutta
Wallich was also temporarily appointed superintendent of the Royal Botanic Garden, Calcutta, and later permanently joined the garden in 1817, and served there until 1846, when he retired from the service. Ill health forced Wallich to spend the years 1811–1813 in the more temperate climate of Mauritius, whence he continued his studies. In 1822, at the behest of his friend Sir Stamford Raffles he travelled to Singapore to design the botanical garden. While travelling to Singapore, Wallich fell ill and stayed at Botany Hall to recuperate. During his recuperation, Raffles persuaded him to write a report to the government to start a botanic and experimental garden in Singapore. In November, Wallich submitted a proposal for a botanical garden in Singapore. Wallich would returned to Calcutta the following year.
Wallich prepared a catalogue of more than 20,000 specimens, known informally as the "Wallich Catalogue". The specimens in the catalogue were either collected by Wallich himself or from other collectors around the same period, including Roxburgh, Gomez, Griffith and Wight. The collector of each specimen is clearly cited in the catalogue itself. Today, Wallich's personal collection is housed at the Kew Herbarium as the Wallich Collection. In addition to the specimens there, Wallich also distributed duplicates of his specimens to herbaria, including some to Sir Joseph Banks, which are in the Kew general collection.
He published two books, Tentamen Florae Nepalensis Illustratae and Plantae Asiaticae Rariores, and went on numerous expeditions. One of Wallich's greatest contributions to the field of plant exploration was the assistance he regularly offered to the many plant hunters who stopped in Calcutta on their way to the Himalayas.
The three volumes of Plantae Asiaticae Rariores made use of artists employed by the Calcutta Botanic Garden: 146 drawings by Gorachand, 109 by Vishnupersaud and one work by Rungiah (the artist employed by Robert Wight); the rest of the plates were by John Clark and three by William Griffith. Two hundred and fifty copies of the work were printed, of which 40 were purchased by the East India Company.
