Dahlstedt specialized in research of the plant genera Taraxacum and Hieracium, of which he circumscribed many species.[2] The botanical genus Dahlstedtia from the subfamily
Faboideae is named in his honor, as are taxa with the specific taxa of dahlstedtii, an example being Taraxacum dahlstedtii, a plant sometimes referred to as "Dahlstedt's
dandelion".[3] Dahlstedt edited several
exsiccata series focussed on Hieracium and Taraxacum specimens, an example being the Herbarium Hieraciorum Scandinaviae distributed from 1892 until 1911.[4]
Selected works
"Bidrag Till Sydöstra Sveriges ... Hieracium-flora", etc., (1890).
"Adnotationes de Hieraciis Scandinavicis, Anteckningar till kännedomen om Skandinaviens Hieracium-flora. I. Af Hugo Dahlstedt", (1893).
"Studien über süd- und central-amerikanische Peperomien", (1900); Studies on South and Central American Peperomia".
"Beiträge zur Kenntnis der Hieracium-Flora", (1901); Contributions to the knowledge of Hieracium.
"De Svenska Arterna Av Släktet Taraxacum: Erythrosperma. Obliqua. I.. II." (1921).
"De Svenska Arterna Av Släktet Taraxacum. III. Dissimilia. IV. Palustria. V. Ceratophora. VI. Arctica. VII. Glabra", etc. (1928).
"Ueber einige orientalische Taraxacum-Arten", (1929); On some Oriental Taraxacum species.[5]