I remember your parisian tree guards! I was extremely jealous! Still am. ;) Can you post a photos of where you're going to put the roses and the tree guards so we can get a visual?

First, your second guess is correct: plant the rose outside the supports. Planting inside seems logical, but it creates problems with pruning and maintenance in the long run (ask me how I know!). If the plant ever needs to be moved, it can be unwrapped more easily if it's not growing inside/around/over/and through, and you won't have to move the tree guard to dig the rose, lol. Also it's just easier to prune a rose that covers something, rather than growing though something. Planting outside the structure also allows more air circulation in the middle of the plant, helping to keep down disease.

Secondly, if you choose hardy roses, then it doesn't really matter if they are on multiflora stock, so your choice of sources increases dramatically. This pertains mostly to climbers, but if the rose is not cane-hardy for you, the rootstock won't make much difference. If the top dies down every year it will just never be able to make enough growth in a season to cover your tree guards. Also, many once blooming climbers bloom on last year's wood, and would never bloom if they lose their canes every winter. Repeat blooming climbers would be able to produce roses every year on new growth, but never on the long canes you hope for to cover your supports. However, if the rose is cane hardy for you, it will also be root hardy. So, no need for multiflora rootstock; own-root would be fine, and to me, preferable, just be sure to choose roses that will be cane hardy for you.

Again, this only pertains to climbers in cold climates.

John

I think you should do fine in zone 6b with Dr Huey rootstock if you can't get your preferred multiflora. I grow roses on both rootstocks with equal success. You could take a look at the roses on Hortico. I believe most of their roses are grafted on multiflora. I've had good luck with them; some others haven't. Please post your photos again of the tree guards to let us see how much room your roses would have to grow. Are deer a problem in your area? Fungal diseases? Diane

I agree totally with John. Diane

If you like the Austin roses their USA web site has a special page for both climbers and hardy roses. If the same rose appears on both pages it will very likely be your best bet for an Austin rose.