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Page ·arno ~a 2 Restoring the Harvard Yard Landscape Michael Van Valkenburgh and Peter Volume 54 Number 1 1994 Del Tredici 122 The Care and Feeding of the Noble Allee Arnoldia (ISBN 004-2633; USPS 866-100) is Marc Treib published quarterly by the Arnold Arboretum of Harvard University. Second-class postage paid at 24 "A Most Dangerous Tree": The Lombardy Boston, Massachusetts. Poplar in Landscape Gardening Christina D. Wood Subscriptions are $20.00 per calendar year domestic, $25.00 foreign, payable m advance. Single copies are 311 Punctuating the Skyline: Alternatives to $5.00. All remittances must be m U.S. dollars, by the Lombardy Poplar check drawn on a U.S. bank, or by international Karen Madsen money order. Send orders, remittances, change-of- address notices, and all other subscription-related 35 In Memoriam: Jennifer Reimer Quigley communications to: Circulation Manager, Amoldia, S. A. Spongberg The Arnold Arboretum, 125 Arborway, Jamaica Plain, MA 02130-3519. Telephone 617/524-1718 36 Arnold Arboretum Weather Station Data Postmaster: Send address to: changes Cover: Lombardy poplars (Populus nigra ’Itahca’/ at Arnoldia, Circulation Manager Sceaux, France. Photograph by Marc Treib. The Arnold Arboretum 125 Arborway Inside front cover: Newly planted trees m the Jamaica Plam, MA 02130-3519 Tercentenary Theater of Harvard Yard. Photograph by Karen Madsen. Karen Madsen, Editor Inside back cover: Lombardy poplars m Chile. From Editonal Committee the Archives of the Arnold Arboretum. Phyllis Andersen Robert E. Cook Peter Del Tredici Gary Koller Richard Schulhof . ,~ ’ Stephen A. Spongberg , Aznoldia is set m Trump Mediaeval typeface and printed by the Office of the University Pubhsher, Harvard University. Copynght © 1994. The President and Fellows of Harvard College Populus nigra ’Itahca’ 2 The next generation of trees for Harvard Yard (Peter Del Tredici). Restoring the Harvard Yard Landscape {... , Michael Van Valkenburgh and Peter Del Tredici The spirit of Harvard Yard resides in its canopy of trees, tall, reaching groves that define spaces and passageways and create an evocative sense of place. Simplicity and understatement are the prevail- Despite the continual buzz of chainsaws in ing qualities of Harvard Yard’s landscape, the the Yard over the past two decades, few new result of a New England aesthetic that might trees have been planted. As a result, Harvard also be termed frugal elegance. It is an almost now needs to make up for lost time. Almost completely built artifice that has evolved over two hundred trees at semi-mature sizes must more than three centuries of intervention and be planted throughout the larger Harvard Yard transformation. As a composition, the land- area to recreate the presence of the grove. Be- scape and the buildings within Harvard Yard cause trees grow slowly, the need to replant are inseparable. Yet it is the landscape-a the Yard’s canopy has become urgent. In 19911 simple order composed of a continuous ground the University undertook a study of the series plane of grass crossed with paths-that has re- of large and small spaces that constitute tained the more enduring, timeless character. Harvard Yard, broadly defined as the Old Yard, The lawn establishes a base on which a broad the Tercentenary Theater, Seaver Quad, the range of building types in various styles are Science Center Overpass and Memorial Hall, sited. Overhead a high canopy of deciduous Quincy and Prescott Streets. As a first step, an trees completes this majestic landscape. Com- ad hoc tree committee was convened. * The bined, the lawn and the canopy unify the product of this group’s effort, a list of trees spaces of the Yard and engender a unique sense suitable for Harvard Yard, can be seen below. of place. Sixty-eight trees have been planted this spring. The maturity of the tree canopy and the im- Another six will be added this fall and two minent loss of most of the American elms more next spring. have become pressing concerns. A nearly cata- The New Tree strophic number of trees were felled during the Canopy last two decades. Many of these were elms that The predominating American elms (Ulmus were infected with the Dutch elm disease, but americana) have imprinted themselves on all many others succumbed to stresses common who are familiar with the Yard. As a species, to the urban landscape: soil compaction, root the elm is fast growing, readily available, easy damage effected during construction projects, to transplant in large sizes; and highly tolerant salt used for ice melting, and fluctuations in of compacted soils. Its natural form provides a the water table. Still other trees were lost due tall, high-branched canopy. Understandably, it to damage in the snow and ice storms of the was a favorite of our predecessors, but its fate late 1970s and early 1980s. strongly suggests that replanting not be domi- * Bernard Keohan, Robert Lyng, Robert Mortimer, Peter Del Tredici, Michael Van Valkenburgh, and Tim Barner. 4 nated by a single species of trees, which might the larger cuts resulting from the removal of again leave the Yard vulnerable to the devas- more mature branches require more time to tating effect of insects and diseases. All re- heal. Over the next twenty years, additional placements must be well suited to stressful branches will be removed gradually as each urban growing conditions, and in the interests tree increases in height. of a unified composition, trees with odd col- The recommended transplant size for new ored bark, flowers, or leaves should be ex- trees in Harvard Yard is five or six inches in cluded since they would not blend with other diameter at six inches above the ground; this is species. typically a tree about twenty to twenty-eight To recreate a canopy reminiscent of the feet tall. Re-training the form of the trees re- character of the American elms-to retain not quires careful selection of specimens with good only their memorable quality but also unim- structural development and a strong central peded views across the Yard-each of the main leader, rather than trees with several leaders. spaces should be planted with a careful blend Many of the species on the tree committee’s of two, three, or four tree species. In combin- list, including the Japanese pagoda tree ing trees the visual character of each species in (Sophora japonica) and red oak (Quercus - every season of the year must be considered: rubra), lend themselves, with attentive main- the overall form and color when the tree loses tenance, to a high-branched and elmlike form its leaves in the autumn; leaf color in spring, even though their natural character, when summer, and fall; any significant flowers or grown in an open location, is a low-branched fruit. The committee left open the possibility and rounded form. A lightly shaded growing that occasionally an additional, single species environment where there is competition for may be added, or preserved, if it is an existing sunlight alters the growth habit of a tree and tree in good health. For example, the few re- yields a reaching elmlike character. New trees, maining white pines (Pinus strobus) should if carefully located in the light shade of other remain as effective counterpoints to the new trees in the Yard, are encouraged to grow taller canopy. Indeed, a new white pine will be as they reach for the sunlight above. New trees planted this fall, along with a catalpa (Catalpa have not been planted directly under existing speciosa) and a horse chestnut (Aesculus trees, but rather outside their drip line. hippocastanum), not so much for canopy re- Within Harvard Yard there are numerous placement but to help reinforce the existing microclimates that affect tree growth. In se- specimens of the same species. lecting species, the nuances of each planting In replicating the character of the American site have been carefully considered, with elm grove, which retained few branches below particular attention to soil type, drainage, twenty feet above ground level, it must be re- wind, available sunlight and shade, soil mois- membered that once a tree grows a branch, the ture content created by variable drainage height of that branch does not change with conditions, density of traffic, and extent of later growth. For this reason, high-branched pavement coverage, which increases soil tem- specimens have been planted from the incep- peratures in the root zone in summer. Also tion of the Yard’s new grove. Trees grown with considered was the proximity of new trees to lower branches removed to six or seven feet existing large trees, which create root compe- above ground constitutes the minimum stan- tition and shade that affect their development. dard for transplanting into Harvard Yard. At The tree committee recommended that all the time of planting, additional low branches trees in poor condition be removed between have been removed to a height of eight or nine 1993 and 1994. Trees rated in fair condition feet above ground level. Branches should al- may have several years of life remaining and ways be removed when they are quite small, as will not be removed-except for design rea- 5 Newly planted canopy trees in the Old Yard (Karen Madsen).). sons-until they decline further. In some in- with trees, establishes an aura of calm power. stances trees in fair condition remain on our The spirit of the Old Yard is largely attribut- plan; these are especially venerable trees that, able to its enveloping canopy of majestic de- with special care and attention, may survive ciduous trees, which create an embracing for many years. grove. While this grove has been dominated by the American elm for most of the twentieth Old Yard century, other species have been included to To many, the Old Yard is Harvard Yard.

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