Tropical Fruit Forum - International Tropical Fruit Growers

Citrus => Cold Hardy Citrus => Topic started by: Walt on July 26, 2019, 03:40:05 PM

Title: Winter twig die back.
Post by: Walt on July 26, 2019, 03:40:05 PM
I am growing many Poncirus seedling, some for pollen or seeds for breeding.  Most are for rootstocks for grafting.  When they were leafing out this spring, I noticed that many had twigs that had died back some, mostly 15 cm. to 30 cm.  That is just the amount of die back, not size of the seedlings.  Some of the seedlings have been through 7 winters here, and more have been added every year, in hope that I'll some winter hardy seedling to graft onto them.
Several of the seedling had no die back, but nearly half did.
Its not a big deal if a seedling for grafting has die back before grafting.  But when I do graft onto them, 30 cm die back means the scion is dead. 
So what is causing this die back and what can I do to prevent it?
I have seldom lost a whole tree to winter kill.  It seems to me it is only one summers growth I am loosing, maybe less.
Title: Re: Winter twig die back.
Post by: kumin on July 26, 2019, 04:03:54 PM
Walt, are you finding the dieback in the most vigorous seedlings? I saw considerable dieback due to winter cold on the most vigorous, succulent shoots. A few trees haven't made new growth past last winter's dieback at this point.
Title: Re: Winter twig die back.
Post by: Bomand on July 26, 2019, 05:01:05 PM
Sounds like winter kill to me. When poncirus is young or not hardened off 6 will get you some die back. Throw a blanket over it on your hard days and nights......
Title: Re: Winter twig die back.
Post by: Ilya11 on July 26, 2019, 06:33:34 PM
In my climate poncirus often is pushing a late growth at the end of August.
These branches have no time for hardening before the first real frost at the end of November.
To prevent the dieback I trim the new growth at  the end of September, leaving only few leaf nods.