FrostTolerancesUMassCranberryStation ofCranberryFruit

Inthelatesummerandintothefall,cranberryfrosttoleranceisestimatedbasedonthedevelopmentalstageoftheplantsandthecolorofthefruit.Theseestimatesarebasedonobservationsandcontrolledtemperatureexperimentation.Thephotosinthisfactsheetshowthestagesandfruitcolorassociatedwithvariousdegreesofcoldtolerance.Observationsshouldbemadebylookingintothevinecanopy;donotseparatethevinesorremovethefruitoruprights.

Summer–30°Ftolerance

Flowers,pinheads,andsmallberries,Howesshown.

Pinheadsandsizinggreenfruit,Stevensshown.

Whitetolightblushfruit–28°FtoleranceNote:fruitmayhaveayellowishappearance

EarlyBlack Howes BenLearStevens

Deepblushonexposedfruitsurface–27°Ftolerance

EarlyBlack

Howes

BenLear

Note:approaching26°Ftolerance

Stevens

Deepblushoverentirefruit–26°Ftolerance

EarlyBlack

Howes

BenLear

Stevens

Red–25°Ftolerance

EarlyBlack

Howes

BenLear

Stevens

Coldhardinessofcranberryfruit. Newlyformedgreenfruitaresensitivetotemperaturesbelow30°F.Late in thesummer, the fruit turnwhiteandthendevelopa faintblushontheexposedsurfaces.Thistransitionisassociatedwithincreasedhardiness;thefruitwillnowtolerate28°F.Asthefruitcontinuetocolor,hardinessincreasesandthefruitcantolerateincreasinglylowertemperatures(seethetablebelow).For all varieties studied, tolerance is the same for each color through the red stage (25°F tolerance).However,asthefruitreachdeepredandmaroonstages,theirtolerancesdifferbyvarietyandmaturity.

For each of the varieties, maximum cold hardiness (tolerance) was associated with full mature color(marooninthetablebelow)butasnoted,theactualtolerancetemperaturediffered.Atfullmaturity,95%survivalaftershort(1-2hr)exposurestotemperatureaslowas18°FhasbeenobservedinEarlyBlack,Howes,andStevens,BUTnotconsistentlyfromyeartoyear.BenLearneversurvivedtemperaturesbelow24°F. In someyears, over-ripe fruit (2weeks aftermaximumcolor) showed loss of tolerance,with allvarietiesdamagedby22°Forlower.Thetoleranceslistedinthetablebelowandinthephotocaptionsreflectaconservativerepresentationoftheavailableresearchdata.

The fruit tolerancetable isbasedoncolordevelopment,which isusedasavisualguidetoripening,achemicalandphysiologicalprocess. It isnotthecolorthatconfers increasedtolerancetofreezing,butrathertheinternalchemicalandphysiologicalchangesintheberriesthataccompanytheincreaseincolor.Asnotedonpage1,colorshouldbeassessedinthefieldbylookingdownatthevines,sincethelowestfruitburied in thecanopyoften remainwhite late into the season.Thoseberriesare likely somewhatprotected by the vine canopy and the internal chemical/physiological changes that occur even in theabsenceofcolordevelopment.

FrostTolerancesofCranberryFruit

Maturitylevel*

EarlyBlack

Howes

Stevens

BenLearandnewhybrids

Green 30°F 30°F 30°F 30°F

Whitetolightblush 28°F 28°F 28°F 28°FDeepblushexposedsurface 27°F 27°F 27°F 27°F

Deepblush 26°F 26°F 26°F 26°F

Red 25°F 25°F 25°F 25°F

Darkred 24°F 24°F

Deepred 23°F 23°F 23°F 24°F

Maroon(1-2wk.later) 23°F 23-20°F 22°F 24°F

Lateseason(endOct.) 23°F 23°F** 23°F** 24°F

*Notethateachvarietywillreachagivenstageonadifferentdate.Generally,EarlyBlack,BenLear,andmanyofthenewesthybridswillcolorearlyandHowes,Stevens,andsomenewhybridswillcolorlater.**lossoftolerancewhenover-ripe

DarkRed–24°FtoleranceEarlyBlackandHowesonly

EarlyBlack

Howes

DeepRed–Tolerancevariesbyvariety

EarlyBlack23°F

Howes23°F

BenLear24°F

Stevens23°F

Maroon–Tolerancevariesbyvariety1-2weeksafterDeepRed

EarlyBlack23°F

Howes23°F.

Toaslowas20°Finsomeyears;returnto23°Ftwo

weekslater

BenLear24°F(neverlower)

Stevens22°F

returnto23°Fin1-2weeks.

May2019.UMassAmherstCranberryStation.E.Wareham,MA02538http://ag.umass.edu/cranberryAuthor/Photography:CarolynDeMoranvilleAdditionalphotography:KrystalDeMoranville

Thismaterial is based uponwork supported by theNational Institute ofFoodandAgriculture,U.S.DepartmentofAgriculture, theMassachusettsAgricultural Experiment Station and the UMass Cranberry Station underProject No. MAS00999. Additional funding provided by the Cape CodCranberry Growers Association. The University of Massachusetts is anAffirmativeAction/EqualOpportunityInstitution.