Trees
Some of the great arboreta from the eighteenth and nineteenth centuries
were planted for the aesthetics of the landscape or of individual
specimen trees 3
. Others were planted as scientific collections. There
was great excitement about new introductions from far away places,
though it was not known how well or how large many of these species
would grow. Today, many of the early introductions are reaching
maturity; some are now rare in the wild and will need to be propagated
to keep them in cultivation. Maturity and loss of trees in severe storms
in the late twentieth century have given arboreta the opportunity to
consider alternative planting designs based on taxonomic groupings,
geographic origin, aesthetics or where particular species will thrive best.
Often, the choice is a compromise among the different options, as the
purpose and conditions of the arboreta have changed over the years. At
Wakehurst Place, planting is in a geographical arrangement to form ëa
walk through the woodlands of the worldí. Plants from six distinct
geographical regions of the World are featured at the University of
Oxford Harcourt Arboretum, as ëplants from high placesí. At Sheffield
Park in Sussex, some 9000 native and exotic trees and shrubs are being
planted to replace those lost in storms and to evaluate their response to
climate change.
Avenues have long been a traditional way of planting trees, and today
we enjoy the vision of those who planted them more than a century ago.
The redwood avenue of Sequoiadendron giganteum, planted in 1863,
makes a spectacular entrance to Benmore Botanic Garden 3
. The yew
avenue Addisonís Walk at Glasnevin predates the founding of the
Botanic Gardens. Restoration of the arboreteum at Kilmacurragh, Co.
Wexford, has revealed a magnificent yew avenue wide enough for two
carriages to drive side by side, a broad oak avenue and another of
Rhododendron arboreum ñ an amazing site when in flower with a red
carpet of fallen flowers beneath. The avenue of mature monkey puzzles,
Araucaria araucana, is a striking feature at Bicton Park Botanic Garden.
At Knightshayes, a grove of Douglas firs, Psuedotsuga menziesii,
11
planted as an avenue in the 1870s, is now reaching 150 feet. At
Biddulph Grange, the underplanting of the lime avenue on the western
boundary has been restored, with dark-green ivy trained into scalloped
shapes to imitate the shadows cast by the trees.
As historic avenues reach maturity and beyond, their management
becomes a dilemma. Vistas and focal points may be obscured by large
trees; some trees are past their best sooner than others, and decisions
have to be taken about whether to interplant to replace individual trees
or whether to restore the whole avenue in one go. These alternatives are
being considered at Westonbirt Arboretum. At Biddulph Grange, an
avenue of Sequoiadendron giganteum was planted around 1860
alternating with Cedrus deodara which were to be removed after 20
years as the redwoods matured; but, when the time came, the redwoods
were felled instead of the cedars! In 1996, the bold decision was taken to
remove all the remaining trees and restore the whole avenue in one go.
The original design was replicated, replanting S. giganteum and C.
deodara backed by a yew hedge, with Aesculus x carnea grafted from
the original trees on embanked terraces set against dark Pinus nigra, to
form a grand and unusual multilayered avenue. At Dunham Massey,
some 1500ñ2000 trees are being planted as part of major restoration of
oak and beech avenues in the eighteenth-century landscape.
Among recently planted avenues are a 120-foot length of Metasequoia
glyptostroboides planted to mark the 50th anniversary of the Sir Harold
Hillier Gardens and Arboretum in 2003; and an avenue of Quercus
frainetto at the Royal Horticultural Society Garden Hyde Hall.