The family Ephedraceae, of which Ephedra is the only extant genus, are gymnosperms, and generally shrubs, sometimes clambering vines, and rarely, small trees.

[6][9] The oldest known members of the genus are from the Early Cretaceous around 125 million years ago, with records being known from the Aptian-Albian of Argentina,[10] China,[11] Portugal and the United States.

[14] However, pollen modified from the ancestral condition of the genus with branched pseudosulci (grooves), which evolved in parallel in the living North American and Asian lineages is known from the Late Cretaceous, suggesting that the last common ancestor is at least this old.

[13] E. ochreata E. pedunculata E. rupestris E. nevadensis E. californica E. antisyphilitica E. frustillata E. torreyana E. aspera E. trifurca E. breana E. boelckei E. milleri E. chilensis E. triandra E. tweedieana E. andina E. sinica E. regeliana E. rituensis E. monosperma E. lomatolepis E. sarcocarpa E. major E. strobilacea E. somalensis E. pachyclada E. foeminea E. campylopoda E. fragilis E. foliata E. ciliata E. alata E. aphylla E. altissima E. minuta E. gerardiana E. viridis E. likiangensis E. americana E. equisetina E. rhytidosperma E. intermedia E. przewalskii E. distachya E. procera As of June 2021[update], Plants of the World Online accepted the following species:[17] The genus is found worldwide, in desert regions, but not in Australia.

However, researchers have discovered evidence of this drought-resistant plant living over 1,000 km further south at Oldupai Gorge around one million years ago, based on fossil pollen, preserved tap roots, and supporting indicators of arid conditions.

[21] The Ephedra alkaloids, ephedrine and pseudoephedrine – constituents of E. sinica and other members of the genus – have sympathomimetic and decongestant qualities,[22] and have been used as dietary supplements, mainly for weight loss.

[23] Plants of the genus Ephedra, including E. sinica and others, were used in traditional medicine for treating headache and respiratory infections, but there is no scientific evidence they are effective or safe for these purposes.

His work to access Ephedra's active ingredients to isolate a pure pharmaceutical substance led to the systematic production of semi-synthetic derivatives thereof and is still relevant today.

E. sinica and E. distachya usually carry six optically active phenylethylamines, mostly ephedrine and pseudoephedrine with minor amounts of norephedrine, norpseudoephedrine as well as the three methylated analogs.

Based on HPLC analyses in industrial settings, the concentrations of total alkaloids in dried Herba Ephedra ranged between 1 and 4%, and in some cases up to 6%.