Chill Hour and Chill Portion Comparison

Below is a chart created by Dr. Greg Reighard that makes a general comparison between chill hours and chill portions.  Please keep in mind that currently, no actual conversion can be made from chill hours to chill portions or vice versa.  The chart is based on field observations which were related to both chill hour and chill portions accumulation.  Observations will continue over the years so that a clearer picture of the relationship between chill portions to chill hours can be developed.

 

Chill hours and corresponding chill portions required by February 15

Chill Hours Needed

Corresponding Chill Portions

650 hours

~30-35

750 hours

~35-40

800 hours

~40-45

850 hours

~45-50

950 hours

~50-55

1050 hours

~55-60

 


Estimated Chill Portion Requirement Per Variety

Estimated

 

 

 

Chill Portion

Chill Hour

Requirement

Variety

Season

Requirement

30 - 35

June Gold

Early

650

Juneprince

Early

650

Clemson Pride

Mid

700

Desiree

Early

700

Dubois

Mid

700

Flavor Rich

Early

700

35 - 40

Harvester

Mid

750

Bounty

Mid

800

Loring

Mid

800

O'Henry

Late

800

40 - 45

Blazeprince

Late

850

Caro Tiger

Late

850

Challenger

Mid

850

Elberta

Late

850

Fireprince

Mid

850

Flameprince

Late

850

Julyprince

Mid

850

Parade

Late

850

Ruby Prince

Early

850

Scarletprince

Late

850

Winblo

Mid

850

PF Lucky 13

Mid

900

Scarlet Rose

Mid

900

45 - 50

Red Haven

Mid

950

Big Red

Late

1000

Fairtime

Late

1000

Intrepid

Mid

1000

55 - 60

July Rose

Mid

1000

Big George

Late

1050

Contender

Mid

1050