Since my swimming pool froze from edge to edge last January 14, I should have been more ready but I thought I had another month.........

I'm getting lots of different info on cold hardiness. I'm trying to break it down at least into groups. Any opinions of these groupings?:

32 degrees or so:
Mexican Lime
Oro Blanco
Valentine Pomello
Kishu
Page
Pixie
Tango

30 degrees or so:
Minneola
Eureka
Pomona Sweet Lemon (Limetta)

28 degrees or so:
Washington & Cara Cara Navel
Valencia & Smith Valencia
Moro, Tarocco, Sanguinelli Blood Orange
Satsuma Owari
Bearss Lime
Rio Red GF

26 or so:
Meyer
Gold Nugget

No information:
88-2
Kiyomi Tangor
Chandler Pomello

Info on Cocktail shows 20 from LaVerne and 28 from Durling.

Where did you find that!?
Tonight we had 23 °F and all my citrus are outside. Nothing will happen.

I'd break it down in 3 groups:

32F
limes/true lemons/citrons

26F
meyer lemon, oranges, grapefruits, pumelos

below 26F
mandarins

most cold hardy
satsuma

The cold hardiness also depends on the length of freeze and size of tree. Here in SE Texas is depends quite a lot on the weather before the freeze. We can have 80F one day and 20F the next, not good for freeze damage.

The subject is kind of like give me a BLT, hold the bacon, hold the lettuce....

Actually there is no actual temperature, only estimations depending the prior weather, the size and health of the tree, and the length of the freeze. I would definitely put limes and lemons in your first grouping - Millet

Satsumas are by far the most cold hardy. I have had satsuma trees in the ground since 1989 and not even damage here in SE Texas. Smallish grapefruit have been killed back to the stump a couple times. However, mature grapefruit and navel oranges haven't been damaged beyond defoliation. Since then there have been several lows in the lower 20s.

However in 1989 when the low was 10F, both my mature satsuma and kumquat tree were killed along with the rootstocks.

My information came from a variety of choices but mostly from the tags on them from the growers.

I can now see that ALL citrus from Durling say 32 degrees on the tag. LaVerne seems to have a variety of temperatures listed but do still seem conservative. Clausen and Monterey Bar say nothing about temperature. The rest of the info came from books on citrus.

If we toss out the 32 degrees on the Durling tags, I get some more consistency.

It really depends upon many things, but the length and depth of the low temperature are most important. Here in northern California we get lows in the low 20s, but typically only get 6-8 hours maximum below freezing. In fact, we are currently going through one of the most significant freezes this area has seen in 30 years. By tomorrow, we will have had a week of lows in the 20s, with the lowest temperatures last night hitting 21-22 degrees or so. The last time we saw lows like this was in the 1990s when temperatures hit 18-19 degrees.

I have 22 varieties of citrus outside and these would be my observations based upon how the cold effects mature growth on established trees.

Limes: mild damage at around 30 degrees, significant damage at 28 degrees, death at 23-24 degrees

Lemons: mild damage at around 29 degrees, significant damage at 26 degrees, death at 20 degrees

Grapefruit/pomelos: mild damage at around 27 degrees, significant damage at 25 degrees, death around 20 degrees

Oranges, mandarins: mild damage at around 25 degrees, significant damage at 23 degrees, death is somewhere ≤18 degrees

-Brett

Mr. Texas, I agree that Satsumas are quite cold hardy, but not the most cold hardy. I would put Kumquats as the most cold hardy variety of the eatable citrus cultavars. - Millet