Thorns are natural for roses, period. It is very common for traditionally thornless roses to produce some. I grew Annie Laurie McDowell for more than twenty years prior to finding my first thorn on it. Even Banksiae produces prickles occasionally. Thornless climbing roses are really completely against Nature as the "thorns" are what they use to "climb". Here is the link to my earlier thread about Banksiae prickles.

http://forums2.gardenweb.com/forums/load/roses/msg011838132980.html

It is not common for Renae to produce thorns, but it completely genetically possible. Renae sported to a single form for Burling Leong (linked below) and this sport has prickles. If these prickly canes produce single flowers like this sport, you probably have a similar mutation on it. If they produce traditional Renae blooms, it may have mutated to a prickly form, or it may just be doing what it CAN do. If you don't like the prickly canes, prune them off. Kim

Here is a link that might be useful: Burling's Single Renae Sport

Aww... I see. Thanks Kim for such a detailed answer, also the links you provided. Last year's blooms on the thornless canes were double just as Renae would look like. It bloomed in a few flushes from late summer right to autumn. Then from winter onwards began the prickly growths, and no more flowers so far. I guess I'll have to wait to see if the blooms are normal this year.

As for pruning prickly canes, I guess that's currently not an option, because all its new growths have thorns. And the canes came from two grafted buds at that, now all became thorny without exception.

It's placed next to a path with heavy foot traffic, actually a gift to the building where I study in college. But whether it can continue to stay there will depend on it stopping to produce those thorns. So I really hope it'll revert back to thornless mode like it was last year. Shall cross my fingers and wait then. Thanks again! ~Hardy

This post was edited by HardyYeh on Fri, May 17, 13 at 14:16

Recently my Renae plant grew a thick basal cane that burst into bloom.
{{gwi:268538}}

The long cane is completely smooth, and the blooms are double.
{{gwi:268539}}

{{gwi:268540}}

I am so glad that all its current growths are completely thornless, and I hope it'll stay that way. Here's a picture of the plant, growing in a large pot next to a gravel path.
{{gwi:268541}}

Lovely! Congratulations! Kim

Oh, good! The smoothness of her canes is one of my favorite features of her, so I'm glad yours has stopped misbehaving ;)

My Renae is always simi double in the spring and very double in the heat of summer, and once in awhile in the twenty some years that I have been growing it a thorn pops up to catch my attention.
I haven't been on this forum in years do to bad health. My garden has suffered greatly because of my health problems but now I am trying to rebuild it. I lost most of my roses during my illness but Renae is one that is still growing and blooming with no change. I just purchased Annie Laurie McDowell can't wait to see how she stacks up in my garden. Great week ahead of me, just picked up a large order of roses from Burlington Roses to start replacing those lost.

Very cool plantings. Good health to you, rosepat.