The air maybe slightly colder but the ground temp will be the same throughout the area.....or within a few degrees.

I wouldn't pile on the mulch but if you feel like it will need more protection, get a couple of bales of straw - should be in garden centers all over the place right now - and use them to build a little barricade around the wire fencing. This will help to insulate both the ground and the tree.

btw, this is frequently grafted to American persimmon rootstock, so may be considerably more root hardy than you'd expect.

is this even a thing in z7?

in my ground freeze MI ... we want the ground to freeze.. and stay frozen all winter .. in snow cover thats pretty easy ... the snow itself keeps winter sun off the dark soil.. so no thawing of the dark soil from winter sun ...

also ... if no snow.. winter winds can pull a lot of moisture out of exposed soil ... and on babe trees .. with not so deep roots ... it could be a problem... since you cant really winter water frozen ground for fear of making an in ground ice cube.. and roots need air as much as moisture .... [not to mention frozen roots that dont really pump water.. and desiccation of evergreen leaves and trunk issues.. in colder zones...]

if your ground does not freeze.. and you could basically water all winter long if need be in some extreme winter drought.. then why waste the mulch ... if you need it elsewhere ...

one of the problems with the WWW .. imo ... is sourcing of website knowledge ... how do you figure out if the source even applies to your location ...

ken

I’ve seen regular Jiro persimmon trees completely top dead after winter but new shoots emerged from the ground. Also a regular seed grown persimmon that my grandma sowed was completely killed one winter after 12 years.. I know that Ichikikei Jiro is supposed to be hardier but I don’t think the difference is to the point this cultivar will not suffer any damage should it be hit with the same harsh winter as the other 2 persimmons I’ve seen did. I will try the bale method. So basically stack the bales all the way to the top of the fence? It’s like 5 feet so about 4 bales stacked on top of each others all the way around, making it a total of about 20-25 bales? I’m not sure if thats what you meant or loosen the bales up and spread them throughout around the fence?

No need to take the bales all the way to the top of the fencing. Just one, or at the most two, will do (intact - do not open and spread out) and form in a triangle around the fencing....so maybe 6 in total. Will certainly contribute to soil insulation and much better than even a thick layer of mulch will do.

Neither the straw bales or any mulch will fully protect the topgrowth so that is a risk you will have to take. Better to know now if that tree is not sufficiently hardy for your area, although with a zone 6 rating, I am not sure what you are so concerned about.

btw, zone 7 soils rarely freeze to any significant depth....a few inches at most. And will take at least 5 days of below freezing temps to get to that point. Soil temperatures change much more slowly than ambient air does. There is also a limit how cold inground soils may get. In your area it would be unusual to see soils drop much below 32F and could be significantly warmer the deeper you go.

IMO, a lot of worry without much cause :-)

Since you have a cage around it already i would wrap heavy frost fabric around the whole thing to protect from dessicating winds which will be more of a problem thsn the temperature imo

I find mulch helps me in all situations when trying to get a plant to survive the winter. It's really cold, dry and windy here.

For example, roses. I literally cover the whole crown of the plant in a mound of bark chips and leaves and I've had good success "zone pushing". I'll stick my finger down into the mound and the soil will be unfrozen, which blows my mind considering the temps we get. Anything that doesn't get covered by mulch is toast, but they seem to grow back fast. Mulch keeps the soil "warm" and I think the roots of a plant like this.