I think it would be best to stake the canes you are worried about. The leaves on the long canes are helping the young plants build mass under the ground for the remainder of this growing season. And yes, the weight of ice or heavy wet snow can break canes.

Remember too that "A Shropshire Lad" is a climber and it wants to have long canes. If you train the canes horizontally along a support rather than trying to prop it up vertically, you'll get that horizontal cane putting up a lot of side canes called "laterals". These are the ones that will put out more blooms, so you don't have a little tuft of blooms at the top of the primary cane like a poodle tail.

In general, you're right that pruning in the fall will stimulate growth, and some well-established roses can handle this fine anyway going into the winter. By next year, you can prune Lady of Shalott back somewhat later in the year if you really need to, though it's more effective earlier in the summer. Remember that the rose will branch off starting at the point you prune it usually, so you want to prune a little lower than the point where you want to see the canes bush out, but not taking off more than 1/3 of the total canes if you can help it.

The main reason I don't do any serious pruning of most roses by this time of the year in zone 5 is that I want maximum surviving cane going into the winter so there is something of substance left in the spring to support new growth. If you prune more off now, then a foot of dead cane from winter exposure leaves you that much less of a rose than if you let the current growth remain through the winter. You do have to watch that the canes have some support, as Michael says, or they can pull away from the base of the rose because of their weight (that's probably what happened with your earlier cane break).

Both of these Austins are likely to be fairly hardy for you, so you can compromise a bit by taking off a bit of the cane, but I'd leave at least 4' of plant if you have it. Something that can help with both support and winter protection is to stack some filled leaf bags around the perimeter of the bush, particularly your climber, leaving some space for air circulation around the rose. In the east coast, you have to be careful not to trap moisture around the rose, except snow that's a very good insulator for roses. You don't really need any winter protection for these roses, but the height and substance of the leaf bags might give your canes something to rest on above the 3' bag so the snow doesn't do much pulling at the base of the plant.

Another option of course is to just do nothing, and that'll probably work too...these are pretty strong roses for you if you have that much growth going on.

Cynthia

Thank you so much for your replies! This is extremely helpful. :)

Tying the canes with jute or wrapping the bottom of the plant with burlap will prevent the canes from breaking off at the bud union if they are covered with heavy snow. Something to remember if you get that unusually early winter storm before the trees have dropped their leaves. My highly effective winter protection consists of wrapping the tender roses with burlap. How many rosarians grow more than 200 roses in Z6 and lose less than one rose a year?

Yes, stake and tie for winter, prune in the spring. You want to leave as much stored energy in those canes as possible for the spring. You will probably still lose some of it to the winter winds but you'll have some left to start out with next season. In at least 40 years of growing roses I've never lost a cane at the bud union to snow weight. Snow is a great insulator and I usually shovel snow on to my roses in the winter.