The herbarium (BALT) was formally organized in 1967 under the directorship of Dr. Mary Castelli. Two years following its establishment, Dr. Donald Windler joined the faculty and became the curator of the collection. Following the retirement of Dr. Windler (in 2003), Dr. Roberts assumed the directorship of the collections after which Dr. Hearn assumed the directorship in 2015. During Dr. Windler’s tenure, the collection grew extensively. The core collection is built around a donation of specimens from the Maryland Natural History Society. The donation includes specimens from as early as 1864 and represents historic records of species distribution in Maryland and the mid-Atlantic region.
In addition to the vascular plant collection BALT houses collections of lichens and bryophytes of Maryland and the northeastern United States. The lichen collection comprises over 3,000 specimens collected by A. C. Skorepa, the prominent lichenologist, and the bryophyte collection was used by colleagues at the Missouri Botanic Gardens as part of their Bryophyte treatment. Since its inception, the herbarium has grown to approximately 60,000 specimens through several large gifts from professional collectors, exchanges with other herbaria, research-based collecting and course-related collecting. BALT is presently the largest active collection on any college or university campus in Maryland and is the only sizable collection on an academic campus in metropolitan Baltimore.
The strength of the collection is in the flora of Maryland and the mid-Atlantic region with representative specimens from other U.S. and international regions. BALT was also envisioned as the repository for a reference collection of cultivated plants in the region making it of interest to horticulturists.