[1] He has collected and described numerous species of plants, particularly in the family Araceae, in his career at the Missouri Botanical Garden.
[2] After serving for about two years in 1956–1958 as a radar technician in the U.S. Army, Croat matriculated at Simpson College, where he graduated in 1962 with a B.A., majoring in botany and minoring in chemistry.
[3] From 1967 to 1971 he studied the flora of Panama with the sponsorship of the Missouri Botanical Garden and the Smithsonian Tropical Research Institute.
Among ongoing projects are dealing with Araceae for the floras of Mesoamerica, Ecuador, Guianas, Bolivia and areas of Colombia and monographs on Dieffenbachia, Rhodospatha, Homalomena and Chlorospatha.
Croat collected his 100,000th specimen, the new species Anthurium centimillesimum, in 2007 in the cloud forest of Ecuador's Pichincha province.