Lehmann conducted explorations in search of specimens of flora in the countries of Ecuador and Colombia over three decades, sending collected material to herbaria in Berlin-Dahlem, Kew, and Saint Petersburg.

[1] He died reportedly of drowning in the Timbique River but his obituarist Kränzlin noted that it was not known if it was by "an unhappy accident or by malice".

[1] Lehmann married Maria Josefa de Mosquera in Colombia and settled in Popayan.

Friedrich Carl Lehmann is commemorated in the scientific name of a species of snake, Atractus lehmanni,[2] which is native to Colombia and Ecuador.

[3] Also, in 1895, botanist Ernest Friedrich Gilg published a genus of flowering plants from Columbia and Peru (belonging to the family Gentianaceae) as Lehmanniella in his honour.