Christian Friedrich Ecklon was trained as an apothecary and also studied botany. To extend his botanical knowledge of regions outside Europe he came to the Cape Colony in October 1823 as assistant to the firm of apothecaries Pallas and Polemann* of Cape Town. He befriended C.F. Drege*, who was also an assistant of the firm at that time. During the next four years Ecklon studied and collected the flora around Cape Town in his spare time. As early as 1825 he presented 350 sheets of dried plants to the South African Museum, founded earlier that year by Dr Andrew Smith*.
In 1827 Ecklon resigned his position to become a full-time commercial collector of natural history specimens, mainly plants. His first batch of specimens was sent that same year to a botanical exchange club, the Unio Itineraria, in Esslingen am Neckar, near Stuttgart, Germany. He prepared a catalogue of some 475 species, mainly Liliaceae and Irideae, which he had collected or received from collectors such as J. Brehm*, W.L. von Buchenroder*, Baron C.F.H. von Ludwig*, and C.L.P. Zeyher*, and which were being cultivated in the garden of advocate J.A. Joubert on the northern slopes of Table Mountain. The garden contained about 1000 indigenous plants, and was probably the first indigenous botanical garden in South Africa. The catalogue, Topographisches Verzeichniss der Pflanzensammlung von C.F. Ecklon... (44p), was published in Esslingen with the assistance of the Unio in 1827. It contains notes on the origin, flowering time and other characteristics of the plants, in some cases complete enough to qualify as valid descriptions of the species. The publication elicited some negative criticism in the form of a letter to the South African Commercial Advertiser signed "J.B.", presumably written by James Bowie*. He complained about the too brief descriptions and some minor matters. Ecklon also published an account (in German) of an excursion to Table Mountain on 16 July 1826, in Flora (1827).
He returned to Europe in 1828 with more specimens, most of which were again distributed by the Unio. With the support of this organisation, and a small income provided by the King of Denmark, he returned to the Cape in 1829 to continue collecting. At this time he reached an agreement with Carl Zeyher to coordinate their botanising and pool the resulting collections. Ecklon started work around Algoa Bay, in the Uitenhage and Albany districts, and as far east as the Ciskei, while Zeyher went to Namaqualand. Ecklon spent some time with von Buchenroder near Uitenhage, where the Drege brothers met him in December 1829. After returning to Cape Town by sea he prepared an article, "A list of plants found in the district of Uitenhage between the months of July 1829 and February 1830, together with a description of some new species", which appeared in the South African Quarterly Journal (1830, Vol. 1(4), pp. 358-380). It listed over 1600 species, contained descriptions of eleven new ones, and as far as is known was the first botanical article of note published in South Africa, and the first locally written publication on plant taxonomy. He also wrote one or more articles, "Kruidkundige beschrijving en aanmerkingen omtrent eenige planten van Zuid-Afrika, welke in de geneeskunde of in het huishoudelijk gebruik nuttig bevonden zijn" (Botanical description and notes on some plants of South Africa that have been found useful in medicine or in household use), which appeared in Het Nederduitsch Zuid-Afrikaansch Tijdschrift during 1826-1831. He undertook several short collecting trips with Zeyher, including one to the mountains near Tulbagh where they collected many interesting mountain plants. Ecklon was a corresponding member of the South African Institution (founded 1829), and later a member of its successor, the South African Literary and Scientific Institution (established in 1832).
Next he and Zeyher undertook a collecting trip lasting almost two years to the eastern border of the colony. They travelled over the Hottentots-Holland Mountains to Caledon, Cape Agulhas and Swellendam, through Kogmanskloof to the Little Karoo, south again to George and Knysna, and through the Langkloof to Uitenhage and Algoa Bay. From there they sent their collections to Cape Town by ship, and set off to collect in the Albany and Somerset East districts and north to the vicinity of present Queenstown. Ecklon returned to Cape Town in 1832 and left for Hamburg to sell their collections. These were made up into five herbaria, varying in size from 500 to 3000 species. He wrote a short account of his travels with Zeyher, "Nachricht ueber die von Ecklon und Zeyher unternommenen Reisen und deren Ausbeute in botanischer Hinsicht", which was published in Linnaea in 1833. It included a catalogue of the seeds and bulbs they had for sale. Meanwhile he prepared a catalogue of Cape plants, with Zeyher as co-author, titled Enumeratio plantarum Africae australis extratropicae. Three parts, totalling 400 pages, were published in Hamburg between December 1834 and June 1837. The work was compiled in haste, with the result that the first two parts appeared before the first part of E. Meyer's work on the plant collection made by C.F. Drege. In recognition of his contributions to botany Ecklon was awarded an honorary Doctor of Philosophy degree by the University of Kiel.
Ecklon made minor contributions to conchology. He collected shells in Algoa Bay and the Albany district and sent them to the Copenhagen Museum.
He returned to Cape Town around the beginning of 1838, but his collecting activities were hampered by poor health and occasional mental instability. In 1843 he was unable to accompany Dr N. Wallich* on lengthy excursions. Except for a visit to Europe in 1844 he seems to have lived an isolated life. In 1851 he was still in poor health and unable to accompany Dr B. Seemann* on an ascent of Table Mountain. However, he did manage to assemble a collection of native remedies at the request of a Cape Town pharmacist, which was sent to the International Exhibition of 1851 in London. After the Danish-Prussian War of 1864 he lost his income from Denmark and had to be supported by friends. He died in Somerset Hospital, Cape Town, at the age of 72.
Descriptions of his plants were published by various botanists, most in Linnaea: The Hepaticae (liverworts) by Lindenberg (1829) and Lehmann (1829-1834); Diosma (Rutaceae) by Steudel in Flora (1830); Bruniaceae, Rutaceae, etc. by Von Schlechtendal (1831); Lycopodiaceae by Kaulfuss (1831); Rubiaceae by Cruse (1832); some 16 families by Bartling and Wendland (1832); and Gramineae and Cyperaceae (1832, 1836), and Acanthaceae (1841) by Nees von Esenbeck. The lichens he collected were enumerated by Stizenberger in 1890. Several taxa were named in his honour, for example the seewead genus Ecklonia; the genus Ecklonea (later renamed Trianoptiles), which includes sea-bamboo; a little sucking fish found among seaweed between East London and Port Alfred, Eckloniaichthys; plant species such as Aloe ecklonis and Plectranthus ecklonii, and the non-marine mollusc Helix ekloniana (based on an incorrect spelling of his name).