Limes (Tilia spp.) are tall treesthat can live for up to 500 years.Tilia flowers at the end of Juneuntil early July, and T. cordata

flowers later than T. platyphyl-los. Mast years are infre-

quent. Tilia sets flowers atthe age of 30, and up to

ten years earlier onsolitary trees. Innorthern Europe,seed regeneration issparse, which isassumed to becaused by low tem-peratures. Tiliaspecies are out-crossing, and atleast some of theindividuals within a

population are self-sterile. Seeds can be

stored for a maximum ofthree - five years.

The trees favour good,loamy sites, but can also be

found on sandy, infertile soils,and are drought resistant. Dor-mant shoots of T. cordata can

Tilia spp.

These Technical Guidelines are intended to assist those who cherish the valuable lime genepooland its inheritance, through conserving valuable seed sources or use in practical forestry. Thefocus is on conserving the genetic diversity of the species at the European scale. Therecommendations provided in this module should be regarded as a commonly agreed basis tobe complemented and further developed in local, national or regional conditions. The Guidelinesare based on the available knowledge of the species and on widely accepted methods for theconservation of forest genetic resources.

Lime

Jan Svejgaard JensenForest and Landscape Research Institute, Hørsholm, Denmark

Technical guidelines for genetic conservation and use

Biology and ecology

EUFORGEN

resist winter frost temperaturesas low as -34°C. In most placesthroughout Europe, T. cordatagrows in several types of mixedspecies forest and many insectsand fungi are associated withTilia. Within the common rangeof the two species, hybridsbetween T. cordata and T. platy-phyllos have been observed.Hybridization and introgressiontake place rarely. Examples ofhybridization include Tilia xeuchlora – a hybrid between T.cordata and T. dasystyla, andTilia x flaccida (between T. platy-phyllos and an Americanspecies, T. americana). Leaf,flower and fruit morphology areused for identification of thespecies.

T. cordata and T. platyphyllostrees easily reproduce vegeta-tively through cuttings and rootlayers, and cuttings caneven be propagatedfrom old trees.Somatic embryogenesishas been carried outboth for T. platyphyl-los and T. cordata.

The ecological range of the mostimportant lime species inEurope, T. cordata, is very broad.T. cordata shares roughly thesame distribution area as Acerplatanoides. It is found in mostaltitudes, and up to 1500 m inthe central Alps. In easternEurope, it is found in purestands, but normally exists inmixed stands.

Three additional species arealso present in Europe: Tiliaplatyphyllos, T. tomentosa and T.dasystyla. The distribution rangeof T. platyphyllos is quite limitedand is commonly found on sitescontaining T. cordata, and is rarein northern Europe. T. tomentosaand T. dasystyla occur in south-eastern Europe and around the

Black Sea.

Climatic conditions and humanimpact have reduced the distri-bution of Tilia in Europe in thepast 2000 years. The competitiveability of beech is also consid-ered as a threat. In many lowlandareas, Tilia may have disap-peared when humans beganfarming these areas, limiting thespecies to marginal sites, and innorthern Europe they are thoughtto have disappeared on manysites due to low seed fertility.However, other stands have evi-dently been established byhumans.

Inbreeding caused by theextensive fragmentation anddestruction of biotopes isexpected to have an impact onboth T. cordata and T. platyphyl-los. Hybridization, introgressionand widespread domesticationof foreign species and prov-enances may also impact theexisting genepool.

Threats togenetic diversity

Distribution

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Investigations of morphologicalcharacteristics of T. cordata haverevealed little variation betweenpopulations (Pigott 1991). Generalgenetic properties have beendescribed by Giertych (inBialobok 1991), but geneticknowledge is sparse. Repro-ductive biology andgenetic variabilityhave beenreported byFromm (2001).As for Quercusrobur and Q.petraea, leaf,flower andfruit morpholo-gy can be used for iden-tification of the species. How-ever, no single morphologicaltrait alone can separate thespecies due to large variationwithin the populations for eachindividual trait (Mauer 1995).

Owing to their aesthetic and cul-tural value as domesticated,urban and landscape trees, limeshave become increasinglyimportant in Europe in recentdecades. The importance of T.cordata in Europe is well illustra-ted by the common use of its

name for geographiclocalities. Tilia wood isused for carving, andalmost all parts of thetree can be used forfodder, ropes or fire-wood. Bast and honey,which were historically

the main products of Tilia,may have been an importantfactor in the spread of thespecies and its statusas a typical agro-

forestry tree in theMiddle Ages. Limetrees are insectpoll inated,and are

important for honeybees andhoney production, especially ineastern Europe. Tilia spp. arealso important for amenity use,shelterbelts and game plantingsin the open landscape, in urbanareas and recreational forestry.

Importance and useGenetic knowledge

p. Tilia spp. Tilia sppp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia

A network of conservationstands is needed to conserve thegenetic variation of limes, whichhave evolved through adaptationto different ecological and envi-ronmental conditions. Conser-vation and breeding programmesin all countries where lime is foundis required to ensure the conser-vation of the genepool. Specificstrategies should include:Sampling strategies: Inven-tories are needed to provide anoverview of the status of geneticconservation in each individualcountry and at the Europeanscale. For practical purposes,provenance regions can be iden-tified on the basis of ecogeo-graphic variation and can bemodified to take into accounteither expected gene flow orgeneral knowledge about gen-etic variation within the species.Central core regions: Largegenetic reserves within the cen-tral core regions of distributionare needed for effective geneconservation purposes andshould be given high priority, aslarge genetic variation is expec-ted to be present in the core dis-tribution area. In general, Tiliaoccurs in mixed species forestand is associated with a numberof different plant species. Exist-ing protected areas will onlypartly serve as genetic conserva-tion areas, as they are not selec-ted at random nor do they coverthe core regions of distribution.

Marginal regions: In someregions, large genereserves of Tilia are lack-ing, and these geneticresources may beextensively frag-mented. They mayalso be subject topollen contami-nation from newplantations origi-nating from non-localseed sources. Forthese situations, in situconservation may not beeffective. In some of themarginal regions the regen-eration of Tilia is lacking orinadequate. Ex situ conser-vation of Tilia geneticresources is therefore rec-ommended in marginalregions. Preferably, these exsitu conservation standsshould be established onthe basis of reproductivematerial from within the localregions, in accordance with insitu silvicultural managementprinciples. In situ conservation inmarginal regions should includea larger number of populations.Use and management ofgenetic resources: Breeding,improvement and managementof genetic resources of Tiliashould be combined with geneconservation to allow evolution-ary forces to continue. Com-bining conservation and use isespecially necessary for speciesof low economic interest (“use itor lose it”). At some locations thelime trees may be eradicated, if

costly and extensive precau-tions are not taken. Alterna-

tively, these resourcescould be used to pro-

mote the establishmentof new populationsfrom local seed collec-tions.

pp. Tilia spp. Tilia a spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeT

Guidelines for geneticconservation and use

Tilia spp. Tilia spLimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.Lim

Distribution range of Tilia cordata.

Distribution range of Tiliaplatyphyllos.

www.euforgen.orgMore information

pp. Tilia spp. Tilia These Technical Guidelines wereproduced by members of theEUFORGEN Noble HardwoodsNetwork. The objective of the Net-work is to identify minimum genet-ic conservation requirements inthe long term in Europe, in orderto reduce the overall conserva-tion cost and to improve the qual-ity of standards in each country.

Citation: Svejgaard Jensen, J.2003. EUFORGEN TechnicalGuidelines for genetic conserva-tion and use for lime (Tilia spp.).International Plant GeneticResources Institute, Rome, Italy.6 pages.

Drawings: Tilia cordata, GiovannaBernetti. © IPGRI, 2003.

ISBN: 92-9043-608-5

EUFORGEN secretariat c/o IPGRIVia dei Tre Denari, 472/a00057 Maccarese (Fiumicino)Rome, ItalyTel. (+39)066118251Fax: (+39)0661979661euf_secretariat@cgiar.org

meTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.LimeTilia spp.

Selected bibliography

Bialobok, S. (ed.). 1991. Nasze Drzewa Lesne. Our Forest Trees. PopularMonograph. Vol 15. Limes - Tilia cordata Mill., Tilia platyphyllos Scop. [inPolish]. Arkadia, Poland.

Fromm, M. 2001. Reproduction of an entomophileuos tree species in low den-sity – Small leaved linden (Tilia cordata Mill.) as an example - Dissertation[in German]. Niedersachsische Staats- und Universitätsbibliothek Göttin-gen, Germany. Http://webdoc.sub.gwdg.de/diss/2001/fromm/fromm.pdf

Mauer, W. 1995. Isoenzymatiche und morphologische untersuchungen zurLinde [in German]. Pp 234-243 in Genetics and silviculture with special ref-erence to native oak species (W. Mauer, and U. Tabel). Mitteilungen aus derForstlichen Versuchsanstalt Rheinland Pfalz 34.

Pigott, C.D. and J.P. Huntley. 1981. Factors controlling the distribution of Tiliacordata at the northern limits of its geographical range. III Nature and caus-es of seed sterility. New Phytologist 87:817-839.

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