Those are tricky questions, and I'm not sure of the answer. But since you're zone 9A I doubt it matters to you. You probably only experience mild freezes, if any, so even 1 year old plants would probably be OK. The ground never gets close to freezing, so even if there was a bit of damage to the top growth, the roots would still be strong and you'd see regrowth with no problems. Heck, in that climate you could probably get away with just placing sticks in the ground in March and letting nature take it's course. Or to increase heat/humidity in spring, you could place inverted cups with small holes over them.

Cold tolerance is tricky to explain accurately, but the best way to put it is like this. Cold tolerance is genetically determined, and all plants propagated from another will have the same genetic level of cold tolerance as the parent material.

Now come the qualifications: There are cultural factors that influence a plant's ability to tolerate cold. Healthy plants, plants with lots of stored nutrients and energy, and slightly drought stressed plants will almost always greater cold tolerance than their less fortunate or well-hydrated counterparts.

Additionally, all tissues do not exhibit the same degree of tolerance to cold. Roots are less hardy than twigs & branches, and all roots are not equally hardy. There is less variability in the hardiness of above ground tissues (on the same plant) than in root tissues. It's important that the fig grower understand that when it comes to roots, it's unwise to test the level of the plants tolerance for cold. This is because roots don't all succumb to cold at the same temperatures. The finest, hair roots begin to die at temperatures as high as 28-32*, with the larger and more lignified roots hanging on much longer. Those that argue against reason by saying, "I left my plant out in 10* weather and it survived just fine" are ignorant of the fact that it's very likely all but the oldest roots died, leaving the grower with essentially a very large cutting that took forever to leaf out in the spring; this, because the tree first had to spend valuable energy it would have used to push the spring flush to root regeneration before it could adequately move water and nutrients to support the canopy.

The freezing of water in the soil isn't a problem, and even the intracellular water in F carica can freeze without damaging the plant. It's when the intercellular water (the water bound within plant cells) freezes that destroys cells & causes tissue death.

Al

Rob,

It was 23 here this morning. Last winter my new that summer in the ground Celeste that had went from 10" to 5' tall froze back to the ground....that was why I was wondering lol.

Is that a record low? FWIW San Jose (9A) averages 40 degrees for a low in Dec/Jan. The lowest it's been this Dec/Jan is 31 and the record for Jan is 24 degrees.

No, not a record. We don't get a lot of cold, maybe 3-4 sub 32 days a year on average but lower 20's do happen here in central Florida on occasion. Our average for January (our coldest month) is 42 low and 70 high.