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Duxbury,Ma.

A good old frost would take out a pumpkin plant, but do we know what temp. the pumpkin plant will actually succumb to. How finicky are they?

5/27/2013 5:22:18 AM

Germany

That´s tricky. One could probably determine the lower limiting parameters for the pumpkin plant to survive, but that´s a function of both temperature and time, and therefore hard to determine. Your frost just isn´t the same frost everywhere around the pumpkin plant. Temperature 1 ft above ground level isn´t the same as temperature 1 ft above ground level under a pumpkin plants leaf, because the leaf will still be heated by some radiation coming from the soil surface. Hence, the third parameter will be soil surface temperature.
To reduce this to just one parameter, you would have to measure the temp exactly in the leaf (or as close as possible to the leaf surface), and then find out which temp goes hand in hand with the death of that part of the leaf. One can assume that this temperature would be pretty much the same for all parts of the plant (there might be little differences between the younger and the older leaves, of course), it would just be a matter of time for the different parts of the plant in different locations to adjust to this temperature.
In summary, a short frost which kills some leaves but doesn´t kill the whole plant doesn´t mean that this temperature wouldn´t be sufficient to kill the whole plant, the time of exposure to that temp could have been too short for some parts of the plant (e.g., those parts closer to the warm soil) to cool down to that temperature. Same temperature for 24 hours might have killed the plant.

5/27/2013 5:54:23 AM

Jericho Vermont

I have had 31-32 degree frosts in the fall with ice crystals on the leaves and have hosed them early in the morning and saved plants. Where I missed with the hose the leaves turned black and mushy by afternoon.

5/27/2013 6:26:39 AM

Albert County, New Brunswick,CANADA

Also in the formula is the humidity - dew point which causes frost to fall on plants as opposed to being just cold and dry.

5/27/2013 7:16:45 AM

Colorado

Ive seen sig. frost damage with lows of 35 to 37 degrees. Covering the plants is 100% effective in that circumstance.

5/27/2013 1:31:28 PM

Menomonie, WI ([email protected])

Radiative cooling occurs and frost appears.Anything below 36 degrees can create frost.

5/27/2013 6:57:47 PM

Zurich, Ontario Canada

Ive been told that if you light a fire, the smoke creates a barrier from frost on a still night. Anyone know if this is is true or just an old wives tale????

5/27/2013 8:22:41 PM

Menomonie, WI ([email protected])

True...smudge pots in Florida in the orchards

5/27/2013 11:21:27 PM

Lloydminster/AB

Last fall I had some several nights in a row with temps flirting with freezing. Interestingly the same temps that nipped the Ags pretty good left my field pumpkins unscathed. The difference was only about 1 degree celcius before both were affected though. -1 celcius in my garden ends it for AGs, 0 and you have a chance.

5/27/2013 11:30:02 PM

Bethlehem CT

The cucurbits seem to be the most sensitive to frost out of everything I grow. I have seem them frost above 32 degrees too.

5/28/2013 8:33:27 AM

Menomonie, WI ([email protected])

At 32 it is froze not frost:)

5/28/2013 1:13:37 PM