New trials and observations

Over 250 species and cultivars have been added to the Arboretum collection since the PRTWO experiment ended in 2001. Most new additions have been species plants for maximum diversity in our limited space. New acquisitions of native Canadian plants are from wild seed sources whenever possible.

New plants growing well in the Arboretum for at least five years include:

Manchurian maple (Acer mandshuricum), three-flowered maple (Acer triflorum), devil's walking stick (Aralia spinosa), American hornbeam (Carpinus caroliniana), Chinese catalpa (Catalpa ovata), buttonbush (Cephalanthus occidentalis), Bunge's ash (Fraxinus bungeana), Fraxinus chinensis subsp. rhynchophylla, dyer's greenweed (Genista tinctoria), Kentucky coffee tree (Gymnocladus dioicus), shrubby St. Johnswort (Hypericum prolificum), butternut (juglans cinerea), Manchurian walnut (Juglans mandschurica), prairie crabapple (Malus ioensis), Sargent crabapple (Malus sargentii), red mulberry (Morus rubra), Korean pine (Pinus koraiensis), Chinese red pine (Pinus tabulaeformis), Chinese wingnut (Pterocarya stenoptera), swamp white oak (Quercus bicolor), diamio or Japanese emperor oak (Quercus dentata), Rosa maximowicziana, apple rose (Rosa villosa), fountain bush (Securinega suffruticosa). 

After the flood... 

An unusually wet year, combined with poor site drainage, caused a flood in the Arboretum in 2010. More wet years followed, keeping the soil saturated and the water table high. Mature trees that have died from wet soil conditions include:

sugar maple (Acer saccharum), black walnut (Juglans nigra), Dahurian larch (Larix  gmelini), Japanese larch (L. kaempferi), Olga bay larch (L. olgensis), Siberian larch (L. siberica), Amur cork tree (Phellodendron amurense), Lavalle cork tree (P. lavallei), Sakhalin cork tree (P. sachalinense), European linden (Tilia cordata).

Arboretum flooding in 2010