The world forest-formation scheme will serve as a guide for adding to the core collections. The staff will have wide latitude to incorporate their unique knowledge of the Arboretum's soils, aspect, slope, drainage, horticultural performance of existing specimens, and other site attributes when choosing the best spot for a new plant not intended for a specific exhibit.

While this plan proposes to clear several undeveloped sections of the Arboretum to create room for new plantings, much of the core collections expansion must take place within the existing collection areas through thinning overstocked stands, removing unhealthy or undocumented specimens, or replacing existing, poorly functioning exhibits. Limited collections expansion onto abandoned sections of road or pathways will also be possible.

Implementation of the Arboretum Plan as proposed will necessitate the repropagation and removal or relocation of both native and cultivated trees at selected spots throughout the Arboretum, especially in areas surrounding the north and south interpretive hubs. It is expected that these losses will be mitigated by new plantings and increased educational effectiveness, thus strengthening both their collection and educational merit.

Repropagation or relocation of existing specimens will be necessary if the Arboretum is to retain its current high level of diversity. Still, it is important to realize that the Arboretum may already have achieved its carrying capacity. Even without the loss of potential core collections area--reassigned in the Arboretum Plan to open space and the native tapestry--sufficient space is probably unavailable to accommodate mature specimens of all the taxa now represented in the collection.