[NAFEX] growing degree days
markl at nytec.com
Thu Sep 23 12:30:33 EDT 2004
I just read a news article that suggests the "growing degree day" model
does not work for all kinds of fruit, most notably apples:
--- from http://www.leelanaunews.com/editorial.php?id=995 (Michigan)
The onset of the fall apple harvest is about a week behind schedule.
Unlike stone fruits such as cherries, peaches and plums, most apple
varieties are not affected by accumulative seasonal temperatures. For
example, the plum harvest is usually completed long before the beginning
of the apple harvest. This year, it's two weeks behind normal.
"Apples respond in a different way," Nugent explained. "You predict the
time of harvest based more on when they reach bloom in the spring and
the temperatures in the weeks right afterward."
There are some exceptions, however. The Gala apple variety behaves more
like a stone fruit, affected greatly by longterm temperature trends.
"Normally, Galas are harvested before (McIntosh). The Mac harvest is
underway and we haven't started Gala yet."
What is the growing model for apples called (bloom time and heat right
after bloom)? And to complicate matter further, some apples like Gala
don't fit the growing model of the typical apple. Curious.
-Mark Lee, Seattle, z8a
From: nafex-bounces at lists.ibiblio.org
[mailto:nafex-bounces at lists.ibiblio.org] On Behalf Of Charles Paradise
Sent: Wednesday, September 22, 2004 8:32 PM
To: North American Fruit Explorers
Subject: Re: [NAFEX] growing degree days
Ron Cadillac of Massachusetts wrote the best article I've seen on degree
days. I think it was in the 1983 edition of the Annual Report of The
Northern Nut Growers Association [NNGA]. If you want to know exactly I
can look it up for you.
Ron did some extrapolations of which pecans would grow at which
locations by comparing the degree days.
Mark Lee wrote:
> This year we had a warm spring and summer. Everything ripened earlier
> than usual. This is a pretty basic question... can the ripening of
> fruit be predicted by cumulative "growing degree days"? Let me know
> I'm correct on this. Here are few ways I would use this information:
> 1. If I keep track of my own fruit ripening times each year in
> degree days (data available at a number of websites), then I should be
> able to predict how late or early a crop will be in years when the
> weather is unusually cold or hot.
> 2. If I wanted to predict how an uncommon plant, like pawpaw, would
> in my own backyard, I would need to find out the growing degree days
> required to fully ripen the fruit. Is that a good assumption?
> 3. If I have a microclimate, like a courtyard, that is much warmer
> the rest of my yard, I would be able to predict what fruits would
> there that would not ripen in the rest of my yard.
> Would I be able to use the growing degree days model in these ways?
> In Seattle this year, we had 2050 growing degree days (50-86F). That
> was hot for us, but pretty wimpy compared to the rest of the country.
> -Mark Lee, Seattle
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