Proper Mulching TechniquesMulching is one of the most beneficial practices a homeowner can use for better tree health.

Mulches are materials placed over the soil surface to maintain moisture and improve soil conditions. Mulching is one of the most beneficial acts a homeowner can do for the health of a tree. However, improper mulching materials and practices may have little, or even negative, impact on the trees in your landscape.

Benefits of Proper Mulching Helpsreducesoilmoisturelossthroughevaporation Helpscontrolweedgerminationandgrowth Insulatessoil,protectingrootsfromextremesummerandwintertemperatures Canimprovesoilbiology,aeration,structure(aggregationofsoilparticles),anddrainageovertime Canimprovesoilfertilityascertainmulchtypesdecompose Inhibitscertainplantdiseases Reducesthelikelihoodoftreedamagefromweedwhackersorthedreadedlawnmowerblight Givesplantingbedsauniform,well-cared-forlook

Treesgrowinginanaturalforestenvironmenthavetheirrootsanchoredinarich,well-aeratedsoilfullofessentialnutrientsandsoilmi-croorganisms.Thesoilisblanketedbyleaves,organicmaterials,andlivingorganismsthatreplenishandrecyclenutrients.Thisenviron-mentisoptimalforrootgrowthandmineraluptake.Urbanlandscapesandnewdevelopments,however,aretypicallyharsherenviron-mentswithpoorqualitysoils,reducedorganicmatter,andlargefluctuationsinsoiltemperatureandmoisture.Applyinga2-to4-inch(5-to10-cm)layeroforganicmulchcanmimicamorenaturalenvironmentandimproveplanthealth.

Types of MulchMulchesareavailableinmanyforms.Thetwomajortypesofmulchareinorganicandorganic.Inorganicmulchesincludevarioustypesofstone,lavarock,pulverizedrubber,geotextilefabrics,andothermaterials.Inorganicmulchesdonotdecomposeanddonotneedtobereplenishedoften.Ontheotherhand,theydonotimprovesoilstructure, addorganicmaterials,orprovidenutrients.Forthesereasons,mosthorticulturistsandarborists prefer organic mulches.

Organicmulchesincludewoodchips,pineneedles,hardwoodandsoftwoodbark, cocoahulls,leaves,compostmixes,andavarietyofotherproductsusuallyderivedfromplants.Organicmulchesdecomposeinthelandscapeatdifferentratesdependingonthematerial,climate,andsoilmicroorganismspresent.Thosethatdecomposefastermustbereplenishedmoreoften.Becausethedecompositionprocessimprovessoilqualityandfertility,manyarboristsandotherlandscapeprofessionalsconsiderthatcharacteristicapositiveone,despitetheaddedmaintenance.

Not Too Much!Asbeneficialasmulchis,toomuchcanbeharmful.Thegenerallyrecommendedmulchingdepthis2to4inches(5to10cm).Un-fortunately,manylandscapesarefallingvictimtoaplagueofovermulching.Mulchvolcanoesareexcessivepilesofmulchmaterialsappliedaroundthebaseoftrees.Whileorganicmulchesmustbereplenishedovertime,buildupcanoccurifreapplicationoutpacesdecompositionorifnewmaterialisaddedsimplytorefreshcolor.Deepmulchcanbeeffectiveinsuppressingweedsandreducingmain-tenance,butitoftencausesadditionalproblems.

Problems Associated with Improper Mulching Onwetsoils,deepmulchcanleadtoexcessmoistureintherootzone,whichcanstresstheplantandcauserootrot.

Pilingmulchagainstthetrunkorstemsofplantscanstressstemtissuesandmayleadtothedevelopmentofinsectanddiseaseproblemsorstemgirdlingroots.

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ThisbrochureisoneinaseriespublishedbytheInternationalSocietyofArboricultureaspartofitsConsumerInformationProgram.Youmayhaveadditionalinterestinthefollowingtitlescurrentlyintheseries:

AvoidingTreeandUtilityConflictsAvoidingTreeDamageDuring ConstructionBenefitsofTreesBuyingHigh-QualityTreesInsectandDiseaseProblems

MatureTreeCareNewTreePlantingPlantHealthCareProperMulchingTechniquesPalms

PruningMatureTreesPruningYoungTreesRecognizingTreeRiskTreatmentofTreesDamaged byConstructionTreeSelectionandPlacement

TreesandTurfTree Values WhyHireanArboristWhyToppingHurtsTrees

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Somemulches,especiallythosecontainingfreshgrassclippings,canaffectsoilpHandmayeventuallyleadtonutrientdeficienciesortoxicbuildups.

Mulchpiledhighagainstthetrunksofyoungtreesmaycreatehabitatsforrodentsthatchewthebarkandcangirdlethetrees.

Thickblanketsoffinemulchcanbecomemattedandmayreducethepenetrationofwaterandair.

Anaerobicsourmulchmaygiveoffpungentodors,andthealcoholsandorganicacidsthatbuildupmaybetoxictoyoungplants.

Proper Mulching Thechoiceofmulchandthemethodofapplicationcanbeimportanttothehealthoflandscapeplants.Thefollowingaresomeguidelinestousewhenapplyingmulch:

Determinewhethersoildrainageisadequateandifthereareplantsthatmaybeaffectedbythechoiceofmulch.Mostcommonlyavailablemulchesworkwellinmostlandscapes.Someplantsmaybenefitfromtheuseofslightlyacidifyingmulch,suchaspinebark.

Forwell-drainedsites,applya2-to4-inch(5-to10-cm)layerofmulch(lessifpoorlydrained).Coarsemulchescanbeappliedslightlydeeperwithoutharm.Placemulchouttotheedgeofatreescrownorbeyond.Remember,ifatreehadasayinthematter,itsentirerootsystem(whichusuallyextendswellbeyondthedripline)wouldbemulched.

Ifmulchisalreadypresent,checkthedepth.Ifsufficientmulchispresent,breakupanymattedlayersandrefreshtheappearancewitharake.Somelandscapemaintenancecompaniesspraymulchwithawater-soluble,vegetable-baseddyetoaddcolortofadedmaterial.

Ifmulchispiledagainstthestemsortreetrunks,pullitbackseveralinches/centimeterssothatthebaseofthetrunkisexposed.Compostedwoodchipscanmakegoodmulch,espe-ciallywhentheyincludesomebarkandleaves.Freshwoodchipsalsomaybeusedaroundestablishedtreesandshrubs.Avoidusingfine,non-compostedwoodchips,assoilnitrogenmaybetakenupbytherootsasthewoodchipsdecompose.