Ripening Analysis

Pawpaw varieties ripen based on a heat unit metric called the Growing Degree Day "GDD".   Some varieties are better suited for climates with a shorter growing season and/or less heat like the Great Lakes, New England, Canada, and the mountains of Appalachia.  Other varieties will not ripen there.  All varieties will ripen in the south, mid-Atlantic, and mid-west.  The following chart ranks the varieties according to the heat units that are required.  It summarizes the results of the Kentucky State Field Trials.  Early ripening varieties are best for areas with a challenged climate for heat.  Late ripening varieties are better for areas in the deep south that have less than about 800 chill hours below 40F.

Sparta, NC Variety Field Trials

Pawpaw fruit-ripening data is under evaluation in Sparta, NC at 3,000 ft elevation in Appalachia.  The location is near the elevation- limit for producing ripe fruit without green-house assistance.  The location reaches a 90F/32C summer temperature maybe once in 8 years.  Low 80s are typical during the day in July and mid 60s at night.  The frost-free season averages 175-180 days at the pawpaw orchard location under evaluation, and we have seen freezing temperatures as late as the second week in May.

The historical temperature data found at Weather Underground  and the Weather Channel seem to be reliable compared to daily observations in Sparta.  

The Growing Degree Day Unit tool from Pioneer was being used to calculate Growing Degree Days (GDDs), but it was found to be unreliable in 2021 and beyond.

The Greencast/Syngenta calculator appears to be a good tool for evaluating growing degree days in the Appalachian Mountains, and it should be a good tool for estimating your growing degree days during your growing season.  

 May 1st is the start date used for accumulation of Growing Degree Day Units.

Year 2021, Sparta, NC

The year was about average for temperatures and rainfall, and it warmed up some in October. 

Trees: 4 KYC, 2 KYC root suckers, 3 Overleese, 1 NC1, 3 Marshmallow, 1 Honey Dew, 4 Tropical Treat, 1 KY Legend, 1 Susquehanna, 1 Lexington Bell

Year 2022, Sparta, NC

The temperatures were warmer than average in the mid-summer but cool days in October cut the growing season short, with an early frost on October 9 leading up to a hard freeze on October 18.  

The Accumulated GDDs were 2619 from May 1- Oct 15,  using Sparta, NC monthly data from Greencast/Syngenta.

The KY Champion midpoint was 2495 GDDs on Sept 23.

Trees: 4 KYC, 2 KYC root suckers, 3 Overleese, 1 NC1, 3 Marshmallow, 1 Honey Dew, 4 Tropical Treat, 1 KY Legend, 1 Susquehanna, 1 Sunflower, 1 Lexington Bell