PRR is the reference herbarium for plants occurring on the Patuxent Research Refuge. The refuge was established in 1936 by executive order of President Franklin D. Roosevelt and is the nation's only national wildlife refuge established to support wildlife research. It is located between Washington and Baltimore.

When the refuge was established in 1936, botanist Neil Hotchkiss and other scientists surveyed the flora on the 2,650 acres which made up the Refuge. Lists of plants found on the Refuge were published in 1940 and 1947. The latter list tabulated 877 plant taxa. Voucher specimens were collected and reposited in the Refuge's herbarium. By 1980, when the refuge expanded to 4,741 acres, a total of 969 plant taxa were listed.

In the early 1990's as part of the Base Re-alignment and Closure (BRAC) process, the Department of Defense transferred about 8,100 acres of land from Fort Meade to the Department of Interior, with control of the land given to the Fish and Wildlife Service. The addition of this parcel, now known as the North Tract, brought the total acreage of the Refuge to over 12,800 acres.

A floral survey of the North Tract began in 2010 and a re-survey of the older parcel of the Refuge, known as the Central and South Tracts, was initiated in 2013. As of November 2020, the herbarium holds over 5,300 voucher specimens from over 1,250 taxa found on the Refuge. This includes some Maryland rare, threatened, and endangered (RTE) species and at least five species new to Maryland. Some duplicate and unique voucher specimens are held by other herbaria.

With the collaboration of the Norton-Brown Herbarium at the University of Maryland, and the Mid-Atlantic Consortium the herbarium is digitizing its voucher specimens collection. Recently, the herbarium has added lichens to its collection.

Please feel free to peruse the herbarium's data, but use it with caution as we are still tweaking things.

For more information