As the leaves continue to fall, our horticulture staff is looking beyond the impending winter to plan for next growing season. One of our most important tasks in fall will be to evaluate plants growing in our nurseries at the Dana Greenhouses as potential new additions to our permanent collections in spring.
By this point, accessions selected to enter the “real world” of our landscape have been under close care and observation in our production facilities for an average of five to seven years. Started as seeds, cuttings, or grafts, plants are transplanted into containers at the greenhouses. These young plants are placed in a cold storage facility and kept at temperatures between 34-38⁰F through the winter, allowing them go dormant while preventing their tender roots from repeated exposure to below-freezing temperatures. After a year or two in containers, plants are transitioned into a shade house. Although transplanted directly into the ground, the soil in the shade house is highly amended to allow for easy root development, and the area is under controlled irrigation and shade. The real test for these young plants comes during their first winter in the shade house, where they receive their initial taste of New England Nor’easters!
Plants are evaluated for hardiness, vigor, and structure for several years before we can determine if they are capable of surviving in our climate. When the time is right, trees are planted in one of three nurseries, and shrubs are transplanted back into containers until they are large enough to graduate to our landscape.
While in the nurseries, plants are further weaned off of their pampered lifestyle through exposure to native soils, full wind and sun, and less irrigation. After putting on several years of growth, they are ready to join the permanent collections. Last month, members of our horticulture team selected over 120 plants that will be planted out next spring. Starting this week, we are busy selecting and marking the locations where they will be installed–not an easy task in a landscape with limited free space after 150 years of planting!
Three specimens of Acer shenkanense (635-2010) are among the plants that will be added in 2015. Grown from seeds collected by Michael Dosmann, Curator of Living Collections, during the 2010 NACPEC (North American – China Plant Exploration Consortium) expedition at Niu Bei Liang National Nature Reserve, China. This is the first specimen of A. shenkanense to be planted in the collections. Note its unique striated bark and multi-stemmed habit.
Another of our 2015 “graduates” is the American witch hazel, Hamamelis virginiana (accession 582-2008). This accession was collected by Arboretum staff, including Plant Propagator Jack Alexander, during the Arboretum’s 2008 Adirondack Expedition in New York. This New England native features bright yellow, four-petaled flowers that appear in late autumn along with bright yellow fall foliage.
A new accession of an old favorite is Acer rubrum ‘Schlesingeri’ (accession 361-2008). The Arboretum’s first director, Charles Sprague Sargent, discovered this remarkable cultivar of red maple, selected for its early, crimson fall color. The original 1888 accession, standing just across Meadow Road from the Hunnewell Building Visitor Center, is an outstanding sight in early autumn.