I donÂt know anything about maples, but if you graft a tender variety of rose on a hardy rootstock, the tender variety will still die if it gets exposed to cold temperatures. IÂm not aware of any research showing that a hardy rootstock increases (slightly) the cold resistance of tender roses, although I suppose it could be possible.

I have read that Rosa canina can increase the hardiness of other roses grafted to it. Apparently a slight incompatibility inhibits the flow of carbohydrates to the roots. The sugars are supposed to act as antifreeze, more or less.

One great advantage a rootstock can bring is to force the scion into earlier dormancy so it avoids early frosts. Most winterkill occurs in early winter rather than late. The trick is to find a stock that is both compatible and able to initiate dormancy. Roses are pretty easy. I don't know about maples.

Karl--do you have that article on R. canina on your website? I'd love to read it. I already have R. canina...

Joan

Joan,

I finally found the article. It's 'Stock-Scion Relationships in Roses' by Griffith Buck (American Rose Annual, 1964). Here's the quotation.

"In the imperfect graft union or the semi-incompatible stock-scion combination, the movement of nutrients within the plant is impeded -producing, usually a dwarfed plant which may or may not flower freely. The dwarfing effect limits the general vigor and vegetative growth of both stock and scion. In a few cases, the early growth of certain stock-scion combinations is typical of the semi-compatible union due to slow regeneration of the tissue systems in the graft union but, with increasing age, this dwarfing effect tends to disappear. This is evident in some of the canina-type understock-scion combinations. It is quite possible that the reputation for superior hardiness which the canina-type understock is supposed to transmit to the scion variety is due chiefly to the lack of complete compatibility between stock and scion with its effect on increasing the starch content of the stems leading to their greater maturity and thus hardiness."

Karl