Frosthardiness experience with citrusvarieties in zone 7, down to 3,2 F

[tedburn]

After more than 10 days freeze down to 14°F or -10 ° C and now 3 days very mild weather I inspected my
inground Citrus.
The following 3 pictures show the current status.


1 year old seedling in pots have been in wintertest, only with fleece protection.
Surprising on right side of picture, Valentine - and Chandler x Bloomseet seedlings with nearly no visible damage.
While 5* citrumelo seedlings, on left side, have burnt tips.


Positive surprise,  Citrangerin, unprotected in first winter with no damage


Positive on left side Bigraft Bloomsweet and Staraji55 under fleeceprotection no damage, in 2. winter.
On right side Slava Micurina with burnt new twigs is deceiving concerning hardiness.

Now hoping that February don' t brings still harder freezes 

[tedburn]

Today I opened the fleece protections of my inground citrus.
The next day s no freeze in sight, so hopefully the coldest time is behind us
Up to no no real harm to the citrus, some minor leaf damage and
some spoiled late sommer twigs.


HRS 899a looks fresh and good, last year first blooms - now 2024
 hopefully  also fruits


Chimera Prag leaves seem partially spoiled, twigs look good


Big surprise is last Sanford Curafora fruit, I left it for freeze test.
Seems to have a good cold hardiness, temperatures in fleece
have been Tmin - 7 or -8 ° C.

[tedburn]

First freeze test this winter with about -8 °C outside in pots under fleece,
one year old seedlings of a cross Chandler pomelo x Bloomsweet grapefruit.
Some look bad but some  look very good and seem to have  a
quite good cold resistance.

[Ilya11]

A little bit surprising to see a bifoliate seedling in this cross.

[caladri]

A little bit surprising to see a bifoliate seedling in this cross.

Do you think that is necessarily more than mere juvenility? I am personally never sure how to judge whether it's young seedlings being weird, or a meaningful difference in morphology, when I see such unexpected leaves, but you have a good deal more experience with such things!

[tedburn]

I also discocered one such bifoliate seedling in a pot of one year old
Valentine pomelo seedlings in the greenhouse.
In spring I will plant them and the Chandler x Bloomsweet in
open ground and see the next winter ( with good passive protection
what will happen.6

[mikkel]

I have an ichangensis seedling that showed this bifoliate pattern on a single leaf.

[tedburn]

A few weeks of mild temperatures after the freezedays
 in January down to - 10 ° C most of the inground citrus
took the freeze very good. My worst/ weakest are:

Slave micurina in the back on the right side.

The others are pretty good.
Left in back Bloomsweet, in front of it Duncan Grapefruit and
in front left Nippon Orangequat.



The weakest of my inground citrus is Ichangensis x sinensis.
even a bark crack see in 2. picture

[tedburn]

Here all the 1 year old seedlings which have seen several freeze days and -8 ° C ,
(pictures of Chandler x Bloomsweet I already posted here) now winter damages shows
from dead/heavy damage (N1 tri Voss) to nearly no damage (Citrumelo N82).
Chandler x Bloomsweet now also shows more damage, but slso some still look quite good
as a positive surprise.
Also very interesting how different the frost hardiness within
one variety.
Because the stickers can' t be red, here the varieties
from left (worst) to right (best):
N1 tri Voss, 5* Citrumelo, Yuzu, Chandler x Bloomsweet, Citrumelo N82

[bussone]

A few weeks of mild temperatures after the freezedays
 in January down to - 10 ° C most of the inground citrus
took the freeze very good. My worst/ weakest are:

Slave micurina in the back on the right side.

What is slave micurina?

[Nemanja]

Slava Michurina (transl. the glory of Michurin) is supposedly a chimera between an orange and poncirus, along the lines of a Prague Citsuma. However, many here in the Forum report that most of the poncirus traits in the chimerism are lost. It's hardiness is questionable at this point.

[tedburn]

Hello Bussone and Nemaja.
@ Nemaja, thanks for the explanation.
@ Bussone, yes Slava micurina was reported to be cold tolerant more than
-10 degrees ° C , but as seen in my picture, at the same location im my gardean
nearby planted Bloomsweet and Duncan Grapefruit show no freeze
damage, while slava shows. So I guess slav is not much more hardy
than already pretty hardy Navel oranges.

[bussone]

Hello Bussone and Nemaja.
@ Nemaja, thanks for the explanation.
@ Bussone, yes Slava micurina was reported to be cold tolerant more than
-10 degrees ° C , but as seen in my picture, at the same location im my gardean
nearby planted Bloomsweet and Duncan Grapefruit show no freeze
damage, while slava shows. So I guess slav is not much more hardy
than already pretty hardy Navel oranges.

Ilya reported it did okay -- better than Thomasville/worse than Morton -- a few years back.
https://tropicalfruitforum.com/index.php?topic=27950.0

[tedburn]

Yes, that' s an interesting report from Ilya and very informative.
But winterhardiness is often very different due to multiple
influences as rootstock, plant age, dormancy,location,....
In the first pictures you see left Bloomsweet with no damage and right
Slava Micurina with some leave damage of small twigs, otherwise
Slava is also O.K.
Good example for influence of only different locations and Rootstock of the same variety in
picture 2 and 3.
Picture 2 Dunstan with late morning sun - very healthy. Rootstock Flying Dragon
Picture3 Dunstan with early morning sun - some spolled twigs. Rootstock Poncirus

[tedburn]

Here the positive surprises of my varieties which managed
the winter very good, conditions this winter I already
described in the previous posts.
Dimicelli  grafted in 2023, very thin graft survived and brings new groth


Staraji55, second winter with new groth, no damage at all


Nippon Orangequat first winter, shows new groth


Satsuma Silverhill,right, and Clemyuz 22 small graft left, both grafts of
2023 on Sanford Curafora no damage at all and with new groth

[tedburn]

In 2023 a lot of new varieties have been grafted or planted in ground.
Two of them are interesting concerning frosthardiness and
better fruit quality ( hopefully   ).

Ichangstar60, grafted in 2021, planted in ground 2023,
no winter damage and now flowerbuds


Trifolis, grafted in 2023 on inground Poncirus,
young graft with no damage in winter and
and now starting to grow

[a_Vivaldi]

What is trifolis?

[bussone]

Madison lists a Citrangequat 10-3-4:
https://madisoncitrusnursery.com/products/citrangequat-hybrid-10-3-4-tree-for-sale?_pos=1&_sid=ede917b52&_ss=r

Anyone know what this is or what it's hardiness is like?

[Perplexed]

don't know, but I bought one to test out in zone 8a.

[tedburn]

What is trifolis?

Trifolis is a Citrumelovariety which is said to have better fruit and
and a very good coldhardiness.

Citrangequat 10-3-4 is as far as I know not available in Europe, at least not under
that name.
We have this, perhaps similar variety:
https://agrumilenzi.it/en/negozio/citrusen/lemons/citrange-quat-4-season-fortunella-margarita-x-poncirus-trifoliata-x-citrus-sinensis/