Scion of an old aristocratic family, he was the son of Conrad Friedrich Robert Heldreich and Amalia Charlotte Humbold. He initially studied
philosophy. A love of
botany, however, took him to
Montpellier in 1837 to study under Professor
Michel Félix Dunal. He later completed his botanical education in
Geneva (1838–1842). In 1841, he was honoured by botanist
Pierre Edmond Boissier, who named a genus of plants (in family
Brassicaceae) from Palestine and Turkey
Heldreichia. His first botanical expedition was to
Sicily, after which he published his first work "Tre nuove specie di piante scoverte nella Sicilia". From 1843 to 1848, he travelled extensively throughout Italy, Greece, Asia Minor and Crete. During 1849 and 1850 he lived in England, and then for a year in
Paris where he served as curator of
P. Barker Webb's herbarium. In 1851, he settled permanently in Greece, where he carried out rigorous botanical investigations. He started to edit at least eight
exsiccata-like series, among them publishing sixteen volumes of the "Herbarium Graecum Normale" between 1856 and 1900 and distributing specimens collected by
Giovanni Battista Samaritani in Egypt under the title
Samaritani delectus plantarum Aegypti inferioris curante Th. de Heldreich. In Greece he served as director of the
court garden for over 50 years, as well as director of the natural history museum, where in addition to the department of botany he helped create departments of zoology and paleontology. It was during this period, in 1862 in
Athens, Heldreich met
John Stuart Mill who was travelling through Greece with his stepdaughter,
Helen Taylor (feminist), collecting specimens of the Greek flora. Heldreich and Mill discussed plant identifications and exchanged collections. Their meeting is documented in John Stuart Mill's botanical notebooks lodged in the Archives of the
London School of Economics. A portion of the John Stuart Mill Herbarium, believed to be in the vicinity of 4000 specimens, is housed at the
National Herbarium of Victoria (MEL) and within this portion are contained a set of Heldreich specimens, primarily from the
Attica and
Crete regions of Greece. Heldreich discovered seven new genera and 700 new species of plants, 70 of which bear his name. Between 1880 and 1883 he taught natural history to the children of the royal family. In 1855 Theodor von Heldreich married Sofia, daughter of I. Katakouzinos and granddaughter of Greek scholar and patriot, Konstantinos Koumas. With Sofia he had two daughters, Karolina, who married Gangolf von Kieseritzky, Curator of Antiquities at the Imperial Hermitage Museum in
St. Petersburg, and Ioanna, who married
Mark Mindler, attorney and head of the stenographer's office of the
Greek Parliament. Theodor von Heldreich was a good friend of
Charles Darwin. He died in
Athens on 7 September 1902. His grave can still be found in the
First Cemetery of Athens. ==Standard author abbreviation==