Employed as a surgeon with the merchant navy, from 1855 to 1857 he collected plants in Tahiti with gardener-botanist Jean Armand Isidore Pancher.
Afterwards, he spent a number of years conducting botanical investigations in New Caledonia, where he was a colleague to naturalist Émile Deplanche.
Within this time period, he also collected ferns in New Zealand (1861) and visited the Cape of Good Hope and the island of Réunion.
[1][2] The plant genus Vieillardia was named in his honor by Jean Xavier Hyacinthe Montrouzier in 1860.
[4] His name is also associated with a species of reptile found in New Caledonia, "Vieillard's chameleon gecko" (Eurydactylodes vieillardi).