[1][2] Per Axel Rydberg was born in Odh, Västergötland, Sweden and emigrated to the United States in 1882.

[3] After he graduated, Rydberg received a commission from the United States Department of Agriculture to undertake a botanical exploration of western Nebraska.

In 1901 he visited Kew Gardens in England and made a return trip to Sweden as well.

In 1905 he was collecting in Utah with visits to the University of Wyoming, Los Angeles, and San Francisco.

Benson, Adolph B.; Naboth Hedin (1969) Swedes In America (New York: Haskel House Publishers)