Monday, May 6, 2013

Heat units for determining blueberry ripening dates

According the the NCSU heat unit model, blueberry ripening is a few days behind schedule. Blackberries don't have the same model (yet), but based on the extended cool spring temperatures so far, blackberry ripening dates may be late as well. 

Read on for more information about the blueberry model.

NCSU has developed a model to predict fruit ripening in blueberry. The growers use it in combination with chilling units to determine ripening dates for the current season. Here is a link to their model.

The Model begins when there is 25% petal fall on Croatian at Ideal farm near Wilmington NC,  and ends when there is 25% ripe fruit on the same bushes.  This year the  model began on April 17th.  The daily values are calculated based on average hourly temperatures through each day.

The model is as follows:
Average hourly temperatures 65 and above count as a point
Average hourly temperatures from 55 to 64.9 count as a half a point.
Average hourly temperatures from 45 to 54.9 have no value
Average hourly temperatures below 45 you loose a point.

According to Benny Bloodworth, NCSU researcher, "Comparing what we have so far to other seasons we are quite a few days behind schedule at this point.  Once we get to the first week in May we will be able to draw more definite conclusions about ripening dates for the 2013 blueberry season."

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