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In page Ulmus glabra 'Horizontalis':

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'Horizontalis' has branches that extend out horizontally with weeping branchlets. It is usually grafted onto a tall understock of Ulmus glabra to effectively display its weeping habit. The tree can eventually grow to a height of 20 metres with a similar spread.[1] It can be distinguished from the related Camperdown Elm by its more spreading and flattened canopy and much larger mature size, although its shape does vary widely, as noted by Loudon: "A beautiful...tree generally growing to one side, spreading its branches out in a fan-like manner...sometimes horizontally and at other times almost perpendicularly downwards so that the head of the tree exhibits great variety of shape".[2]