North American Fruit Explorers mailing list at ibiblio

["Mark & Helen Angermayer" <hangermayer@isp.com>]

Thanks Jerry,

 

Great explanation.

 

Mark

KS

----- Original Message -----

From: Jerry

To: nafex@lists.ibiblio.org

Sent: Tuesday, December 18, 2007 8:25 AM

Subject: Re: [NAFEX] Grafting prunus (as opposed to budding)

In a message dated 12/17/2007 10:03:27 PM Eastern Standard Time, hangermayer@isp.com writes:

Question on the aluminum foil.  Do you know how high temps have to get to be adverse to callusing?  If I remember right the Nafex handbook said something about temps above 90 degrees can cause graft failures.  So would the grafts reach those temperatures in the springtime without shade?

Hi Mark,

That is difficult to answer. The later in spring the greater the chances of temps high enough to cause failure. Some years back I made a number of persimmon grafts, some with foil, some w/o. The foil protected grafts had a higher percentage of takes but I didn't record the numbers. Just proved to myself that foil is beneficial.   

The following is not by personally testing but by others who have. Wood slows or halts growth at about 90 degrees F. Doesn't kill it, that takes higher temps, but don't know what. And suspect that can vary with the species. I believe the bigger factor damaging grafts is the scion drying too much before callusing to the understock, and heat will hasten that.

I've successfully grafted (not many) here in the later part of April by watching the weather forecast. If they say you will have about three days reaching lower 80's and night time temps not below 60, graft.  Not often we get that kind of range.

My opinion of the bottom line on using foil is, us it. Temps falling lower than 60 will not kill the scion, just slows healing, but high temps can. Better to keep it cool than allowing the sun to cook it.

Let me tell of one experience I had. I did a Bark graft grafting a Juglans hybrid onto pure black walnut. It was early spring and the understock was bleeding badly. I made the cuts to relieve the bleeding at the graft site, but it flooded the graft anyway. I had totally covered the graft with Parafilm. About two weeks later there was no sign of callusing, not surprising with bleeding walnut. The bleeding had stopped, so I took out the scion which was still nice and green, cut off the understock about 2 inches lower, retrimmed the scion to clean wood and once again placed then scion into the understock. It took!!  The first graft had a foil shield.      

Another note, flooding doesn't cause persimmon grafts to fail. I've had many flood the Parafilm filling it, and the liquid turns black, but takes. 

Jerry 



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