Join us in our campaign to re-establish the
elm across the British Isles
Since the 1970s over 20 million elms have been lost to the ravages of Dutch Elm Disease in the UK alone. This huge loss has caused a dramatic change to our landscape as well as removing the natural habitat of many organisms. Knoll Gardens is actively working to restore this lost heritage. |
![]() |
|
Vigorous foliage of young Princeton elm |
Why are elms grown on their own roots superior? |
||
| Dutch Elm Disease can be passed from tree-to-tree via intertwined roots. These are just as susceptible to the fungus as the tops of the trees. A beetle carrying the fungus can infect one tree and before long a whole area of elms could be decimated via root-to-root transmission.
Until recently, it was only possible to reliably produce elms by grafting their cuttings onto seedling elm rootstock that had no resistance to DED. As the trees were then still vulnerable to disease some growers began grafting onto Siberian elm, (Ulmus pumila) rootstock. This presented different problems. Described by noted horticultural writer Dr Michael Dirr as 'one of, if not the, world’s worst trees', the greater concern with using this rootstock is one of long term incompatibility. For a large elm such as Princeton to have the roots of a tree that attains only half its average mature size can only result in an inadequate root system, albeit one that |
![]() |
|
| may not become fully evident for decades to come. | Lord Montagu plants Princeton at Beaulieu |
|
|
||
![]() |
Since most who plant large trees do so with the hopes that the tree may live for centuries to come, elms grown on their own root represent our best hope for the future.
Published results from a recently concluded, 20 year research study conducted by Ohio State University, show that trees grown from cuttings on their own root average 56% greater caliper and canopy volume than trees grafted onto seedling rootstock. |
|
elm rooted liner |
|
|
![]() |
We are the sole UK supplier of the incredibly disease tolerant Princeton elm, Ulmus americana ‘Princeton’, a fast–growing tree with a classic elm shape and large leathery leaves. In its native USA 80 year old Princeton elms remain in perfect condition. It is this combination of disease tolerance and proven longevity that makes the Princeton elm unique and so well suited to our cause. | |
Young Princeton establishing in the UK. Photo courtesy of Butterfly Conservation |
| How you can help……….plant an elm for future generations Princeton elms are the perfect selection for gardens, arboreta, parks, estates and street plantings: anywhere a large, graceful and long-lived specimen tree would enhance the beauty of the landscape is the perfect spot for a Princeton elm! Shipped from the USA in winter, while dormant, barerooted elms are best planted during the winter period, though containerized trees can be planted at any time of year if watered sufficiently. |
![]() |
|
Roy Lancaster plants first tree in UK soil at Knoll Gardens |
The country unites to re-establish the elm
|
![]() |
The Prince of Wales and The Duchess of Cornwall plant the disease tolerant Princeton Elm (Ulmus americana ‘Princeton’) at Highgrove with The Column Bird ‘eye-catcher’ in the background. |
The science behind our success
|
![]() |
Field production of young ‘Princetons in the USA |
| Tried and tested In the early 1990's, the USDA National Arboretum tested several selected varieties, seedlings and hybrids of elms by injecting them with artificially severe doses of the most aggressive strain of Dutch elm disease. The Princeton elm had a 96% survival rate. No other variety of DED susceptible, large-leafed elm can boast this combination of disease resistance and longevity in the landscape. |
![]() |
Chelsea Gold Medallists |
||||||||||||||||||||||||||||||||||||||||||||||
For current availability, sizes and pricing please go to our online store or call us on 01202 873931 |
Garden Design? Our personal consultancy service can now bring Knoll's style into your own garden. Find out how |
Need help choosing ? Click Here to see our list of Plants for Specific Places |
![]() |