Parker was born March 31, 1882, in Corinne, Utah, but grew up in West Central, Spokane, Washington, USA.
He gained BS (1923) and MS (1929) degrees in botany from the department of plant pathology at State College, Washington.
[7] Among the students who studied botany at Howard University at this time was Marie Clark Taylor who succeeded him as departmental chair in 1947.
[6] As a mycologist, he specialised in the taxonomy of the Basidiomycota, especially Hypholoma, where he provided the first systematic treatment of species found in the USA.
[13] The flower species Lathryus parkeri (H.St.John) was named after him[12] and subsequently merged into Lathyrus nevadensis var.