Reading through member comments here, I agree this is a wonderful rootstock plant for warmer zones--7 and above. I haven't seen anyone comment on just WHY it is so great. Here's my attempt. I have grown roses grafted on it in zones 8b and 9a(Coastal Alabama years ago and now southeastern Louisiana). About a third of my roses at this point--not including minis--are grafted onto fortuniana. (I have not yet learned the art of grafting onto Fortuniana; otherwise I would have more). The first year or so, people new to Fortuniana will wonder what all the fuss is about. But by the third year and beyond, they'll understand. Among the small handful of commercially used rootstocks, this is unrivaled. I saw a positive comment from southern California. But here on the Gulf Coast, particularly in Florida, there is a specific destructive pest that Fortuniana is ideally suited for handling well. It is a soil nematode that multiplies over time if plants it likes to feed on are available. Roses are a feast for this (root-rot) nematode. In Central and South Florida particularly, roses plants on their own roots or other rootstocks typically start out fine, by year 4, 5, or 6, most languish and keep declining, often dying off over winter or from fungal diseases because of their nematode-weakened state. Not roses on Fortuniana. This has a uniquely hyper-fibrous root system so vigorous that the nematodes cannot keep up with it. It lacks the thick tap roots of Dr. Huey or even the medium size thick speghetti-type roots of Multiflora, which is why it will benefit greatly from being staked the first two or three years. But what you get for that trade-off is not only strong resistance to that nematode, which admittedly doesn't live everywhere; you get much more ability of the roots to take up nutrients, as it is those little white, fibrous, feeder roots that are the lifeline of roses. Fortuniana roots are virtually all feeder roots.

Additionally, because they lack long tap-roots, they are far better a choice for growing in large pots than are the California standard Dr. Huey budded roses. Potted or in-ground, roses grafted onto Fortuniana, by year three start to pull ahead of their counterparts in size and number of branches and blooms. I have done experiments growing the same rose on its own roots, or Dr. Huey, and then on Fortuniana. Fortuniana, with rare exception, is up to 50% larger. those exceptions are the occasional varieties that have great roots of their own. I have grown the AARS winner Hybrid Tea Paradise on Dr. Huey, own-root, and now Fortuniana. Honestly, that rose is fantastic on its own roots; one of the best of the 20th Century hybrid teas in that sense. But even it is performing somewhat better on Fortuniana.

To repeat, Fortuniana is a slow starter, fussy to graft onto, and not quick out of the gates, but for long-term performance in warmer climates, it can't be beat.

ps: I have been a renter for most of my 40+ years growing roses, so have often been limited to growing roses in pots. For that reason, I shied away from growing any enormous roses. I am excited to have my own house finally, as of a year ago, and I have started a baby Fortuniana I rooted from a cutting of a sucker growth last fall. I am eagerly awaiting this to grow into an enormous shrub in my side yard. My plans are for it's own lovely spring flowers, to be a scaffold for Clematis flowering vines, and to supply me with plenty of cuttings on which to practice grafting. Who knows, I might get the hang of that art. ;)