Hello,

I belive there is methode to reduce the risk of frost damage on hardy or semi hardy citrus. It is some kind of high level grafting. My personal experiences shows that the most critical part of the plant during strong frost periodes is the part right above the root level. In the past I lost some citrus because of damage exactely at this certain part eventhougt I used lots of mulch to cover the soil and parts of the plants.

Below pls find 2 photos to show what I mean:





As a conclusion it is advised to keep the Poncirus in this critical part growing and to put the grafting at a higher level of the rootstock in order to reduce the risk of damage.

Below 2 photos of a Hybrid US 852 to show it practically



Plant in total





brgds

I have some plants with both low and high grafts (directly to the rootstock). They all survived our recent 23 F freeze with protection. I also have several grafts I put on my sisters' trees and have examined they briefly about a week after the freeze--they were exposed to 17 F. All of the grafts I put on Vicki's satsumas appeared to be OK--Without any protection! The grafts (with significant growth) are oranges and a pomello. These grafts are on the upper canopy and were fully exposed to high winds and cold!

The grafts on Beth's trees were given some protection (covered with canvas drop cloths). The Lisbon lemon on Star Ruby gft was partially defoliated, but oranges were not. The mandarin I put on a Meyer seedling was hit hard-- the seedling is only about 1 ft (30 cm) tall-- the graft was about 8-10 inches (20-25 cm) above ground--it may not survive.

Andy,

I agree about protecting the trunk. Over here, if worse comes to worst, we can scoot over to Home Depot and buy tubular foam insulation that we can simply snap unto the trunk of the tree. We primarily use the same tubular foam insulation to prevent water pipe freezing and bursting over during record breaking freezes, and the same insulation can be easily snapped around the trunk, starting from the base of the tree. This is in addition to protecting the canopy from above.

Regards,

Joe

P.S.
I'm in the US and could not find US 852 rootstock anywhere. How in the world did you manage to get yours?

Hi Joe,

I got my Hybrid US-852 from a special citrus nursery nearby and they received seed material direct from the breeders in Florida.

Myselfe I one´ce ordered and received Hybrid US 812 (which seems to be also very hardy) direct from the Bureau of citrus budwood registration in Winter Haven. I mailed to Michel Kesinger and he managed the shipping. I belive if he is still in charge of these matters he will help to get material.

Try to get in contact via the mail adresses mentionned at the following webside

http://www.doacs.state.fl.us/pi/budwood/arb.html

More information you to Hybrid US 852 you can find here at the breeders page:

http://www.ars-grin.gov/ars/SoAtlantic/fp/hb/bowman/rootstock.html

and at this PDF file

http://broker10.fcla.edu/DLData/SN/SN00971219/0112/1999_112_54_55_Bowman.pdf

Good luck

best regards from Hamburg

Thanks a lot!

There seems to be some hidden rivalries between citrus growers of Florida and California, that is why the rootstocks developed in Florida is having a hard time finding their way here. Perhaps people in the intermediary states can request the seeds and later relay to me.

Of course, right now it is the USDA that has put a quarentine on any citrus from Florida with the except for fruit that has to be from inspected groves.
I am not certain, but I don't think seeds can be exported from the state.