It is important to note here that IR thermometers don't actually measure actual temperature, they measure apparent emmisivitty (different materials will have different emmisivities even at the same temperature) , therefore to get a somewhat good reading you would need to measure the apparent reading of a frost cloth at a known ambient temperature and calculate the difference. In other words measure a frost cloth that is hanging up outdoors for comparison with the one over the heated plant.

No, actually I think in windier conditions, that's when the bag is more effective. Anything that blocks the movement of air is going to help slow down the loss of heat.

I think in zone 8b Yuzu is barely going to need any protection, and is probably going to be able to survive on its own through the Winter, but you may still want to bag younger plants. It is one of the most cold hardy citrus, probably just a little cold hardier than kumquat.

I have all of my citrus covered now too, the cover blew off of one of my mature Satsumas overnight, thankfully the temperature was only down to about 28 this morning, with 14F in the forecast for tonight. I was able to get it covered back this morning in the sleet and freezing rain, the covers on all the smaller citrus are frozen solid even though they each have a string of C7 christmas lights (about 215 watts per tree), so I have my fingers crossed here too.

Parker

Do you think a Meiwa kumquat on Kuharske Citrange would be more, or less hardy than a Meiwa kumquat on its own roots. Perhaps not different either way. Kuharske is probably a 10F or colder tree. My US897 roots are probably a 15F to 20F maximum cold tolerance rating I have Seville seedlings still under the sprouting soil. The Seville rootstock promotes the highest soluble solids, grows well with salt, grows well in clay, grows well higher PH does very well in soggy soil comparatively.

Steve