Current Collection Statistics

The living collection is the term we use when referring collectively to all accessioned plants growing at the Arboretum.  Arboretum staff are continually assessing and evaluating the health of the plants, their relevance to our mission, potential for invasiveness, and their aesthetic value.  As a result of this ongoing assessment we regularly remove plants from the living collection for a variety of reasons, but our plant exploration, seed collection, and plant acquisition activities provide a constant flow of new plants into the living collection that provide opportunities for evaluation, research, study and appreciation of the beauty and diversity of the plant world.

Below is an overview of living collection composition and taxa representation. Data are current as of January 1, 2018.   

Understanding the Table

Collections.  When new propagules (seed, cuttings, and plants) arrive at PHA, they are assigned a unique ‘Accession number’ that remains with the propagule(s) forever, even after they are removed (deaccessioned) from the living collection.  The PHA accession number format (for example, 2012-005-C) denotes the fifth accession in 2012, and ‘C’ indicates there are at least 3 (A, B, C) items.  In simplest terms, items are duplicate copies of the same accession.  All values presented above exclude Accessions currently held within propagation culture (namely, all seed collections for 2017).  

Taxa.  A taxon (plural – taxa) is a unit of classification.  The plant kingdom is divided and subdivided into successively smaller taxonomic units.  Family, genus (plural – genera) and species are the three most widely used by gardeners and botanists.  A family is a group of closely related genera and a genus is a group of closely related species.  For example, the heath family (Ericaceae) includes many genera, such as Rhododendron, which in turn contains many species such as rosebay rhododendron (Rhododendron maximum), flame azalea (Rhododendron calendulaceum) and Catawba rhododendron (Rhododendron catawbiense).

Pteridophytes are a primitive group of vascular plants (primarily ferns) which do not produce flowers or seeds.  This group predates both gymnosperms and angiosperms, originating well over 300 million years ago.  The pteridophytes are today represented by some 11,000 species worldwide.

Gymnosperms are seed-bearing plants of which conifers are the most well-kown examples.  Translated literally from the Greek, “gymnosperm” means “naked seed” referring to the manner in which the seeds are borne, often in cones or cone-like structures.  Pines, spruces, firs, junipers and cedars are some of the more common gymnosperms well represented at PHA.  Ginkgo, dawn redwood, Siberian carpet and the South American monkey-puzzle are some of the less well-known examples found throughout the Arboretum.

Angiosperms are the flowering plants, the largest and most diverse group of plants on earth.  Unlike the gymnosperms from which they evolved nearly 200 million years ago, angiosperm reproduction involves ‘double fertilization’ of both the embryo and endosperm.  Many significant PHA collections are angiosperms, including Stewartia, Rhododendron, Ilex (hollies), and Hydrangea.