Hillier Trees | Ulmus ‘New Horizon’ | Resistant Elm
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Royal Horticultural Society

World Record Holder for Gold Medals at RHS Chelsea Flower Show

Ulmus ‘New Horizon’

"Resistant Elm"

Common Name

"Resistant Elm"


12m high x 4.5m wide after 25 years. Ultimately Medium/large


100% Dutch Elm Disease Free; all soil types; urban conditions; coastal conditions; very high and very low temperatures; windy conditions.


Becoming rounded with age and requires similar space as Tilia cordata


Fresh green even in drought conditions, turns yellow-ish in autumn.


Host to the rare White-letter Hairsteak Bufferfly.

Ulmus New Horizon is a medium to large tree which is completely resistant to Dutch Elm Disease (DED).  It needs a similar space to grow as Tilia cordata.  In maturity it forms an attractive rounded canopy with fresh green leaves.  The leaves continue to look fresh even in drought conditions.

This exciting elm shares the same phenology as the native elm and as such is a host to the extremely rare White-letter Hairstreak Butterfly (WLH).  The WLH butterfly is native to the UK and an endangered species as DED all but decimated their natural habitat.  The Butterfly Conservation organisation have been monitoring the population grow on a stand of Ulmus New Horizon growing in Vauxhall Spring Gardens, London.

This tough tree is a fast grower and quick to establish itself.  This has made the tree a popular alternative to Fraxinus which is no longer available due to a ban on the movement of ash trees in the UK.

The particular qualities of interest are: DED free; native wildlife habitat including the rare White-letter Hairstreak butterfly; fully hardy in extreme cold; drought resistance; tolerant of periodical waterlogging; mid green leaf colour; yellow autumn colour; thrives in coastal conditions and poor soils.

The above characteristics have seen it successfully planted in: SUDS schemes; car parks; central reservations on the highway; harsh urban developments; coastal plantings including as pleached screening; rural avenues and as a specimen tree.

The parentage of this hybrid is Ulmus japonica and Ulmus pumila.  The initial hybridisation took place at Wisconsin University over 60 years ago.

This elm is fully tested through inoculation of the fungus that causes DED.

Read our case study on the development of the Dutch Elm Disease resistant Ulmus 'New Horizon.