It depends on the type of rose. In my garden, the Gallicas get Autumn colors well before even the first light frosts, so their leaves are already "on their way out" so to speak. The Bourbons and HPs generally start getting more blackspot around first-frost time, so I guess that's their "Autumn colors". Most of those leaves fall off shortly after.

So what I think you're asking about is what happens to actively-growing leaves when they experience a cold snap. Well, that I can also tell you. Here, it's not a light frost that does them in. It's more like temperatures below 25F. Initially, they don't look any different. But when it warms up again to above freezing, the leaves have a sort of "freeze-dried" look to them -- as though wilted, but still maintaining rigidity. If you see leaves that are turning yellow in color but are otherwise of "normal" texture, I'd say it has to to more with extra water than freezing temperatures. But take that with a grain of salt -- our conditions are very different.

:-)

~Christopher

I looked at the pics in the other thread and look just as many of my roses do when we have one of our normal chilly and wettish winters. This is just leaves senating in my opinion. This is not freeze damage it is just the winter effect.

In my z4 area, the leaves of cane hardy roses, such as 'John Davis', turn colors and drop off like a deciduous shrub in the late fall. Roses that are not cane hardy & normally die back to the root crown, such as HT's, will remain green right up to frost & hold their leafs into the winter. As the winter progresses along, wind & snow will knock most of these leaves off also. Below is a pic of some HT's, grandifloras & floribundas in mid Dec in my garden.

Jackie my cultivars like rugosa and some older ones ie Gartendirektor Otto Linne the leaves change color and fall from the rose. Most of my moderns do not lose their leaves as they do not enter true dormancy (deciduous). After several bouts of below zero weather they take on an appearance of freezer burn with some still greenish looking. some do not lose their leaves at all but are removed during spring pruning.

Many HT, Austins and the like, also Chinas do that for me in mid winter just before pruning time. I help the rest of the leaves off during pruning. I guess than in colder climates they just don't have the time to react before freezing temps stunt them. Temps in the 30s and 40s do it over here.

It's 18F outside and windy. Just went out took 2 photos, photo 1 the leaves still frozen on the rose bushes, Photo 2 rose bushes are leaveless. Sooner or later all the leaves will be gone, we had a warm Nov and Dec. I don't remember the leaves turn yellow first before falling out though. It's more like the 1st photo, frozen leaves before falling off. But I am in a different zone.