CHILL HOURS

flowers of Prunus armeniaca Français : Fleurs ...

flowers of Prunus armeniaca Français : Fleurs d’abricotier (Prunus armeniaca). (Photo credit: Wikipedia)

 

 

 

 

 

 

 

There are several guidelines to follow for maximum crop yield for fruit with chill hours:

  • Select varieties that have a chilling requirement no more than 20% less than local averages.

Selecting a low chill variety in a cold area will result in trees flowering too early and being damaged by late frosts.

Selecting a high chill variety in warm areas will result in little or no fruit production.

  • Early flowering varieties are best in warm climates, late flowering varieties are best in cooler areas.
  • Early ripening varieties are best in areas with intense summers, late ripening varieties are best in cooler summers.
  • Climate extremes may eliminate certain varieties that would otherwise meet the chilling requirements, eg frost and wind events at bud break
  • Trees propagated from existing trees that are acclimatised to your climate are likely to do better than those imported from other regions
  • Latitude, terrain  and microclimate can affect the chilling hours received. Open slopes may receive more chilling hours than sheltered areas next to warm buildings.
Average Temperature Winter Chill Units

0

1250

7.9

1100

10.2

800

12.7

600

13.1

520

13.6

500

14

450

15.3

330

15.5

300

19.7

0

http://www.bom.gov.au/climate/data/index.shtml and

http://www.eldersweather.com.au can give you an idea of your suburbs average number of chill days by postcode

 

City Average Temperature of COLDEST MONTH Approximate Winter Chill Units High, Medium or Low Chill?
Sydney 12.2 640 Medium
Newcastle 12.6 600 Medium
Wollongong 13.3 510 Medium
Launceston 7.4 1100+ High

Various sellers of fruit trees publish significantly varying chilling hour requirements for the same variety. It is difficult to know the exact requirements. Experiment and ask around for local cultivar success stories…

Common Name Genus & Species Chill hours
Blueberry Vaccinium spp 350-1100
Rabbit-eye

Southern Highbush

Highbush

350-800

400

800-1100

Apricot Prunus armeniaca 400-1000
Chestnut Castanea spp 450-650
Pecan Carya illinoinensis 500 (300-1000)
Grape – Muscadine Vitis rotundifolia 500-1000
Plums Prunus spp 500-1200
Japanese plums

Greengages

European plums

500-800

600-800

> 1000

Peach & Nectarine Prunus persica 600-1000
Pears Pyrus spp 600-1000
Asian Pears (Nashi)

European Pears

600

600-1000

Pistachio Pistacia vera 600-1500
Kiwifruit Actinidia deliciosa 600-880
Walnut Juglans spp 700-1500
Gooseberry Ribes spp 800-1500
Currants Ribes spp 800-1600
Raspberry Rubus spp 800-1600
Hazelnut Corylus avellana 800-1600
Cranberry Vaccinium spp About 800?
Grapes – American Vitis labrusca 1000-1400
Apples Malus spp 1000-1600
Feijoa Feijoa sellowiana >75
Lychee Litchi chinensis 100-200
Pomegranate Punica granatum 100-200
Persimmon Diospyros kaki 100-200
Quince Cydonia oblonga 100-400
Figs Ficus carica 100-500
Grapes – European Vitis vinifera 100-500
Strawberry Fragaria x Ananassa 200-400
Olives Olea europaea 200-600
Almond Prunus dulcis 300-500
Kumquat Fortunella 300-500
Mulberry Morus spp 400

http://scpa.org.au/bvssfruitchillhours.html has other plants you might consider.

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3 thoughts on “CHILL HOURS

  1. I’m extremely sorry but i have had no experience with gooseberry bushes so I’m afraid I am unable to help you with that.

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