Come-back of elm in the Netherlands

Jelle Hiemstra (WUR-PPO)

October 9, 2013; 3rd International Elm Symposium

The Elm in the Netherlands

3 native species

● U. laevis, U. glabra, U. minor

● Many hybrids: a.o. U. x hollandica

Unique combination of characteristics ideal street tree

● No specific requirements concerning soil type

● Able to resist (sea)wind

● Very good recovery from mechanical damage

● Stands de-icing salt and paved surfaces well

● Open crown

Plaatjes

Early 20th century: • Elm dominant tree in landscape • 1.5 M elms (2 M poplars) • 99% U. x hollandica

Dutch Elm Disease

1st epidemic: 1920-

● Ophiostoma ulmi (Ceratocystis ulmi)

● Loss of most Dutch elms (U. x hollandica)

● Replaced by: U. minor; ‘Commelin’, ‘Vegeta’

2nd epidemic: after 1972

● Ophiostoma novo-ulmi; more aggressive

● High mortality: U. minor / ‘Commelin’ en ‘Vegeta’

Resistance breeding program (1928-1992)

Clonal selections from native species

● 1936: ‘Christina Buisman’ – very susceptible to Nectria

● 1947: ‘Bea Schwarz’ – bad form and growth

New clonal selections from European species crossings

● 1960: ‘Commelin’ – very susceptible to O. novo-ulmi

● 1963: ‘Groeneveld’ – resistant to some extent

Crossings with resistant asian species (U. wallichiana)

● 1973: ‘Lobel’, ‘Dodoens’ and ‘Plantijn’ – moderately resistant

● 1983: ‘Clusius’ – moderately resistant

● 1989: ‘Columella’ – highly resistent

USA: ‘Resista-clones; ‘Pioneer’, ‘Homestead’

Situation around 1990

New “resistant” varieties available

Continuing losses by DED in old varieties

Number of elms planted decreased very strongly

● 1995: elm not in top 25 of nursery trees

Elm street trees endangered by extinction

2005 survey: future of elm in NL ?

● Enquiry among urban green managers

● Literature study

● Workshop with elm experts

Conclusions

1. We need the elm as a street tree

* No real substitute

2. Resistant elm varieties are available

3. Problem

● Lack of faith in DED-resistance

● Lack of information on characteristics

Testing and demonstration needed

Project Future for the Elm (2006-2012)

Aim: Restore faith in the elm as street tree

Main activities ● Resistance testing of recent elm-varieties

● Research into propagation and stability

● Investigate growth characteristics & suitability as street tree

● Communication of results (Building an “Elm-website”)

Cooperation ● Research: PPO + Alterra

● City of Amsterdam + other cities

● Tree nursery industry: Bonte Hoek Nursery

Financing: Product Board of Horticulture

Results

Experimental field

● 29 varieties

● > 1000 plants

Resistance testing

● All presently in NL available cultivars

● Conclusion: ample R-cultivars available

Propagation and stability

● Conclusion:

If propagated adequately stability no problem

Growth characteristics as street tree

Test present varieties under Dutch conditions

Network of test plots established

● Cooperation with several cities

● Several cultivars in same plantation/area

● Several trees (5-10) of each cultivar

● Plantings under different conditions (area’s)

● Amsterdam: Port-area + new urban area IJburg

● Additional plantings in other cities

Rotterdam, den Haag, Deventer, Boxtel, Westland

Iepen in praktijkbeplantingen

A

IJ

A

H

W D B R d

H ? A

IJ

A

H

W D B R d

H ?

Commelin

Groeneveld

Lobel

Dodoens

Plantijn

Clusius

Columella

Nanguen (LUTÈCE)

Ulmus laevis

pumila 'DenHaag'

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Cathedral

New Horizon

Regal

Rebona

Sapp. A. Gold

Homestead

Pioneer

Urban

San Zanobi

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Amsterdam- Port area

16 varieties

150 trees

spring 2007

Amsterdam- IJburg Amsterdam- IJburg ● 15 varieties

● 131 (+) trees

● 2007-2011

Amsterdam- IJburg

Communication

Publications in trade and growers journals: ca. 20

Articles in nationwide (2) and regional newspapers

Presentations: 16 (4 internat.)

Elm-DVD

Video on YouTube

Elm dossier on website of Wageningen-UR

Radio interviews: 2

Website: www.straatbomen.nl elm project page

Other initiatives

City of Amsterdam

● Long standing sanitation programme

● Replanting of elm trees

● Promoting elm as ideal street tree

Nursery specialised in elm trees

● Promote elm as street tree

● Participate in research and communication

Regional initiatives: Iepenwacht (Frl, Gr, ZH)

● Sanitation programme DED losses <1%

● Replanting elms (2012-2016); Frl:8500; Gr:3500

Do all these initiatives have effect?

Poll in newsletter for tree growers

Question:

Does research into resistance stimulate the demand for elms

Reactions:

Total 88

Yes 75%

No 25%

Elm gradually returning in Dutch streets

Conclusion

Good and resistant elm varieties available

The combined efforts of research, urban green managers and tree growers are having effect

Common opinion on elms has changed

● Importance in nursery industry is increasing

● More cities are planting elms again

Things left to do:

● Continue street tree testing of new elm varieties

● Communication on characteristics of elm

Thank you for

your attention

J.A. Hiemstra

PPO-Bomen

Postbus 85

2160 AB Lisse NL

Jelle.hiemstra@wur.nl