José Mariano Mociño and
Martín de Sessé worked on a
Flora Mexicana and after de Sessé's death in 1808, Mociño met de Candolle in 1813 in
Montpellier and showed him the drawings they had produced for the planned work. De Candolle requested that the plates be copied by artists of the Geneva community. Of these copied plates, the sixteen done by Heyland caught de Candolle's eye. Guided by de Candolle he became one of the leading botanical artists of the period, working for him for 24 years. One of his students was
Jean-Louis Berlandier who also showed great aptitude in his botanical illustrations. Becoming a citizen of Geneva in 1819, Heyland was admitted to the Society of Arts and the Swiss Society of Natural Sciences. The
Archduke Reynier, Viceroy of Lombardy, commissioned him in 1849 to work at the botanical garden in
Monza. In 1859 he returned to Geneva, where he lived on the proceeds from the lessons he gave in drawing. From 1835 he worked as principal artist on
Charles Antoine Lemaire's
Jardin Fleuriste. He drew and engraved 5 full-page illustrations, including
Impatiens parviflora for de Candolle's
Quatrieme Notice sur Les Plantes Rares. Between 1839 and 1846 he produced the illustrations for volumes 4-5 of
Icones selectae plantarum, another of de Candolle's projects in collaboration with Benjamin Delessert (1773-1847). He carried out several commissions for the Geneva Botanical Garden, and directed the engraving and printing in colour of the 180 plates used for 'Voyage botanique en Espagne'. ==Later life and legacy==