The Alexandra Botanic Garden contains many woody specimens planted in family collections.
Notable trees include a Kentucky coffee tree (Gymnocladus dioicus), Japanese weeping cherry (Prunus yedoensis 'Shindare yoshino'), tulip tree (Liriodendron tulipifera), dawn redwood (Metasequoia glyptostroboides) and some 300 year old white oaks (Quercus alba) that pre-date the founding of the college. A small brook known as the Silver Thread winds through the garden from a waterfall at the east end of the campus and empties into Paramecium Pond.
The garden is home to Paramecium Pond, the most prominent landmark in the Botanic Gardens. This groundwater-fed pond supports many aquatic plant and animal species, including birches (Betula spp.), azaleas (Rhododendron spp.) , highbush blueberries (Vaccinium corymbosum) and water lilies (Nymphaea odorata). The pond is very popular with visitors and the college community as a relaxation and bird-watching spot.
The child for whom this garden was named was the daughter of Cordenio and Mary Severance, a member of the college's Class of 1885. Alexandra died at the age of six, and her parents wished to memorialize her with a garden that would perpetually bear the little girl's name. Its beauty was to reflect Alexandra's own. In 1906, the Severances donated funds to establish the Alexandra Botanic Garden.