Just so that folks don't get confused, pointing out that HMF says that r. gigantea grows in climate zones"8 and higher". This includes almost the entire West Coast all the way up to Canada, parts of Alaska, the entire US South and the US South East, and almost all of Virginia (see map below). Those are not "the tropics". Warm weather roses also grow happily all around the Mediterranean, (including famously in Southern France), and in South Africa, and many non-tropical parts of Asia and Australia, among other Temperate climate places. Not trying to be too picky, but IMO is it important to let folks know that what I call "warm weather roses", like r. gigantea and its hybrids, and tea roses, and china roses, can be grown in much of the US, and other places all around the world which do not have Tropical climates.

Of course I agree that it would be lovely if they also grew everywhere, but that is one of the beauties of roses - there are types which thrive in warm, and hot, and also cold climates.

Jackie

You could always plant Montecito. It's huge with huge single, marvelously scented blooms. It's also more cold hardy and significantly easier to grow than Gigantea. The Brunonii genes helped greatly. I never had any issues growing Montecito but Gigantea has committed suicide on me twice. It's as intractable as Sinowilsonii. https://www.helpmefind.com/gardening/l.php?l=2.19363

There is or was a Brunonii eating a two story structure in the rose garden associated with the RiverBend zoo in Columbia SC. The base of that bush looked as if it were growing out over the bricks and paving stones daily.

Roses Unlimited has imported a number of roses from India with Gigantea in their breeding and we haven't heard much good or bad about them.

With RRv still doing a number on my roses, I'm hesitant to keep trying to find something with some resistance to RRv.

Were I twenty years younger, I'd do a "camellia test" plant as many seedlings of gigantea as I could find and see which ones, if any, make it through winter.

I feel as if the early imports into Charleston had a much lower virus (not RRv) load and were stronger. Heck, I've got a seedling noisette that outperforms my other ten noisettes and as it ages it's seldom out of bloom.

Valuable comments here. Is the genetic capacity for getting huge linked to a lack of hardiness to cold? I was trying to think of an alternative speculation, but none came to mind; i.e., a rose that was cane-hardy in zones 6 and colder could theoretically turn into a giant, as it wouldn't have to replace its woody growth annually. Do cold hardy climbers like 'New Dawn' get bigger in warmer climates? Does a longer growing season or more days with temperatures above a certain level cause hardy roses to grow larger? (We know the answer for warm climate roses: look at the Teas and English roses and how they grow in Mediterranean climates compared with how they grow in Great Britain.)

Re R. brunonii behavior, I grow 'La Mortola', thought to be a hybrid of R. brunonii, and it does show a tendency to become a monster, not to mention being the thorniest rose I know. It's perched on a rock shelf below a terrace wall and struggled for years, not showing any willingness to climb up into the massive bay laurel next to it, and not having anywhere else to go. Then, a couple of years ago, DH built a pergola for it above the terrace wall. We tied canes of 'La Mortola' on to the railing that topped the terrace wall, and then trained them up onto the top of the pergola. This year LM has embraced the pergola, sending out 3'-4' new canes from the canes trained up there, and possibly even ready to attempt the bay laurel from its new, more advantageous position.

@jacqueline9CA

Agree with that statement. However I also would like to add that, most so called 'tropical roses' aren't truly tropical. I should know because I live in a tropical climate and R.gigantea, RXfortuneana etc refuses to flower here because of a lack of winter chill. R.gigantea usually grows at higher elevations where the climate classification is really Cfb, Cwb, Cfc or Cwc, meaning temperate high altitude climates. I was told that R.clinophylla and maybe R.bracteata are the exceptions and that they flower in a truly tropical climate (I am yet to confirm this, but they grow to be enormous thorny monsters). Don't get me wrong, gigantea as a plant might grow to be enormous in the tropics but that doesn't mean it would flower or complete its reproductive cycle. The same is true for Rxfortuneana, some wild multiflora hybrids, R.Leschenaultiana etc.