Rose bush growth in the fall

I live on a property in north Idaho that used to be a cattle pasture. It is covered in a large amount of nonnative dog roses, which some say are "invasive" in our area, but I really like them for many reasons.  

Something interesting I have noticed about them that I have not seen on any other shrub in our area is a burst of new growth in the fall before our cold winter season sets it. Now to some this might not seem that interesting, but to me it is quite so.

Our climate here could be considered a cold mediterranean climate. We have cold wet winters and dry summers. All of the other shrub species in our area have a burst of growth in mid to late spring while temperatures are rising and humidity is still quite high. By mid summer, however, their growth comes to a halt with the onset of hot dry weather and they pretty much are done growing until the following spring.

However, after our dry summers we have a short period of time in the fall where the humidity rises with the first fall rains and before the real cold of winter has set in. This period is a short "second growing season" for our area and a lot of cool season plants like grasses and forbs will put on a little bit of green before winter fully sets in. I have not noticed any other woody plants taking advantage of this second growing season except for these introduced roses.

They start growing new stems, thorns and leaves that have the soft and flexible texture of new growth like they do in the spring. These tender tips are a favorite of our sheep during this time when there is not a lot of other fresh new growth. I also believe the deer in our area relish these as well and I have noticed increased populations of them in these "invaded" rose habitats. In fact during hunting season I specifically seek these areas out in order to increase my chances at harvesting a large buck.

Anyways I am a pretty huge plant nerd and for some reason this seems really cool to me so I thought I would share it with other potential plant nerds who might find it interesting as well.

Neat observations. Are those multiflora rose (Rosa multiflora)? I don't see them having a second flush of growth in fall here, but they usually bloom in June and mature the hips during the summer. If in your area they fail to set fruits in early summer, and weather is favorable in fall, it may coax them to grow and bloom again.

You know, my wife and I made a remark this fall about a 'new' rose bush we planted in the spring having a second flush of buds forming and thinking it was odd.  I wish I could identify it for you but it was a big box store clearance plant who was supposed to produce yellow roses but instead made ones of dark red. A mystery if you will.

I can't tell you any rhyme or reason for it, perhaps the weather 'tricked' the roses for another boost of growth? Perhaps it is normal?

We should circle back in a year unless someone else has an answer for us.