The Tropical Fruit Forum

https://www.growingproduce.com/citrus/georgia-citrus-seeking-to-make-its-mark/

This year's talks were recorded.  Some of the topics are:
Dr. Juan Carlos Melgar, Clemson U - Winners and Losers from the 2022 Christmas freeze. 
Hershell Boyd, Madison Citrus - From Zero to 200 Citrus Varieties in 2 Years. 
2023 SE Citrus Expo - Confessions of Certified Citruholics 
Many thanks to Derick Nantz for his efforts.   
 https://www.youtube.com/watch?v=VmGyHdsSsGc&list=PLz1OK2nyDTOCgLBukjR7pfXOKK5lv76Ye

On the old forum there was a topic about grafting a sprouted seed onto a rootstock. 

 Diluted latex with water sounds like a great idea.  I am going to try it too.  Will paint the bottom few inches of some trees which have lost all bark from the winter events, will try bridge grafting and inarching.

From the Southeastern Citrus Expo

 "Dr. Christopher Vincent, Associate Professor Horticultural Sciences University of Florida, will share his research on the effects of water and shade on citrus health, citrus greening, and other citrus growing challenges."

He discussed shade on citrus production.  It is a complicated topic, photosynthesis comes to an intermittent stop because of moisture loss in full sun.  When stomata are open, CO2 can enter the leaf, but moisture can leave.  So stomata close to keep moisture in.  It cycles.  Spraying a light blocking film on the leaves improved growth. 

Thank you for creating this resource. 

10 Degree Tangerine 3-3 died at 9 F. -12.8 C
10 Degree Tangerine 2-2 survived
CiClem 10 is approximately as hardy as 2-2
Curafora barely survived

Citrus can be covered with a tarp for the winter and left that way for months without damage.  They don't have to be repeatedly covered and uncovered.  This has been discussed here and in the older forum a few times. 
However, if there is a heavy snow on the tarp it can can break the underlying branches unless there is some additional support.

A tree in Massachusetts kept under a tarp and warmed with aquarium heater in a water barrel kept fruit that were found to be
edible when uncovered in the spring.

I think "orange" fits well for Poncirus. I have let the juice stand for one night in an open glas, then threw away the bottom fraction and made lemonade from the rest of the juice. It tasted primarily orange-like, not like a lemon (by the way better than both).

I ask myself though how it happend that the overall bad taste of Poncirus developed. What was its evolutionary advantage? What kind of animals love exactly that taste? I have picked up somewhere that the taste is designed for antelopes. Can that be true?
Well, animals sometimes have a very different taste from ourselves. Rabbits like bitter meadow. Many animals eat conifers. ... It could also be that some animals that are ruminants find fresh poncirus fruits just acceptable but love the taste of fermented fruits - I mean when they eat them a second time (ruminated). As I wrote above the bad flavour of Poncirus vaporizes over night totally (in case of better tasting fruits) or at least largely (in case of bad tasting fruits). The chemical changes in a rumina will be much greater.

Interesting speculation about antelopes Till.  Fruit needs to pass through the body and survive, or partially eaten and some seed survive.  .  Transport of seeds by animals is called zoochory. I can't find specific information about citrus zoochory.  Speculating on poncirus, especially with the large number of thorns, it doesn't want it's fruit to be eaten before the seed is ripe, thorns protect the fruit and the tree.  When the fruit are ripe, they drop to the ground and are more readily available.  The fruit resins which may keep the fruit from rotting degrade, and the fruit could become more palatable.  Some animals that eat citrus are rats, monkeys, red panda, some bird species. 

8 F, 13 C was not cold enough to differentiate a lot between most hardy citrus.  Both types of 10 Degree Tangerine appear to be more sensitive to the cold than expected, leaves curled more than most.  Brown Select, Changsha, Keraji appear to have done well.  Sugar Belle will probably lose its leaves, but seems to have survived.

As Millet said, more time was needed to find the true amount of damage, which was much worse than initially appeared.  Posted elsewhere on this forum are the evaluations.

My US 119 died.  It was covered with a tarp but otherwise not protected. It was planted last summer so was just a couple feet tall.  Low was about 9 F, -13 C. Unknown what temperature the plant endured, it was surprising that the ground did not release sufficient heat for a relatively cold hardy plant to survive. 

https://www-tropusikert-hu.translate.goog/eml/poncirus.html?_x_tr_sl=id&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp

Could try green bulbs.
Plants do not utilize the green portion of the visible light spectrum as much as it does on the red or blue/violet end.
So theoretically, a green bulb would disturb the plant less than a white, red, or blu/violet bulb would.

Plants are green because they do not use green light.  Putting green light on a plant will not give it the energy it needs to grow.  Citrus needs to rest.  Long term exposure to 24 hour light is harmful. 

Hello, I am in a zone 5b part of michigan and want to grow citrus. I read that FD can handle -20c which is about the average winter low here. I would prefer to not have to add extra winter protection. I am wondering if there is a form of poncirus trifoliata that can handle a few degrees colder so I have a little more wiggle room in terms of cold tolerance.

I grew Poncirus in Vermont.  There is a posting somewhere of someone growing it in zone 4 with frost cloth.  It is not the cold that kills it, but wind and winter sun.  If you can place it out of the wind and in the shade in winter it will survive.