I’ve heard that grafting to a mini rootstock can result in a smaller rose, for instance. I’m surprised such is not done more frequently, particularly given the desire for more compact plants…
That would make sense. It would be akin to dwarfing apple rootstock. Maybe the reason it isn’t done more often is that growers and sellers are going to go with what is tried and true and are reluctant to experiment with new root stocks. It would be very interesting to see a large rambler grafted onto a mini rootstock though, that would cool.
Minis are ‘china rose’ based. and not all minis are small sized roses, just roses that have smaller blossoms.
A corollary would be the interesting habit of a lot of Southern Folks who are into showing minis who graft/bud minis onto R. x fortuniana rootstock. Fortuniana makes big tall to huge climbing roses. Fortuniana when budded with HTs makes big HTs bloom machines that produce a lot more roses than some other rootstocks in the same conditions.
But the mini’s I’ve seen on fortuniana have retained their mini-ness, at least at the beginning of their blooming life.
Do the minis become minifloras when they are fortuniana?
My personal experience is limited, but I grafted a seedling of mine (Carefree Beauty x Rise N Shine) onto Dr. Huey as a half standard (18")tree rose. In 10 years it never did anything other than be itself, outside in summers and inside in a greenhouse during winter.
I believe there was an article on this question in the RHA newsletter or American Rose Annual quite a few years ago. As I recall the author of that concluded that miniatureness in roses is a trait that does not move through the vascular system. I think some of the big rose companies have sold minis or mini-floras as standards that don’t overgrow.
Dwarfing of apples by itself has little effect on leaf, flower or fruit size, it just regulates internode length and vegetative vigor. Even a six inch piece of stem of the right stock cultivar can produce the effect, and some production systems depend on that, with vigorous root systems to assure good anchorage, top-worked with a strongly dwarfing interstem and a standard type on top. I think Tukey at Michigan State wrote a book on this called “Dwarf Fruit Trees”. I have an autographed copy in my work library, from a retired horticulturalist.
We now have genetic dwarfs of peaches, and spur-type selections of apples to do similar things. I can tell you that a spur type apple will not reduce vigor of a standard type grafted onto it. I have tried that several ways.
A mini root system might stunt a HT, or depending on the choice of mini, keep up with it, but I doubt it would change the flower size any more than starvation could. That is the principle of Bonsai, where root restriction and constriction tends to reduce the proportions of the top. But not all species make suitable Bonsai, because they just make less numbers of large leaves, rather than scaling back, when restricted.