The only way that could logically work would be if you had a rose hardy to a zone lower than the root stock to which is was budded. Say a zone 3 rose budded to a zone 5 root stock. Theoretically, that plant would only be a zone 5 plant as the roots could be killed in a zone 4 or lower type weather event. Creating an own root version of the zone 3 plant, once it's mature, would result in a zone 3 hardy plant. Otherwise, no. Zone hardiness is genetic. You could lose a zone with a weak growing, badly grown or immature plant. When you hear of someone pushing a zone, successfully growing a rose less hardy than called for by their zone, it is usually because of either a particularly less severe pattern of weather, or sufficient protection afforded by the micro climate until the "real world" overcomes the artificial environment or unnatural conditions. Kim

No, you can make a rose less hardy by making an own-root version.

The canes are genetically programmed to a certain level of hardiness. Unless the roots are having severe problems getting nutrients from the soil for some reason that a different rootstock would affect, cane hardiness is a given.

Another thing that affects hardiness is vigor. If a rose can easily regrow after being killed to the ground, it will effectively be hardy. Rootstocks give a rose more vigor, so a grafted rose will be hardier than an own-root one.

Not in my garden. all 400 of my roses are on their own roots. Grafted roses are planted deep so the canes above the graft form their own roots. It's often not the root stock or the grafted top that causes a rose to die in winter. Quite often it's a failure of the graft. A bad graft that has some moisture between the root stock and scion can freeze and separate causing the top grafted portion to die as no nutrients or moisture can get to the top. This can happen with the hardiest of roses. I have several own root roses supposedly not hardy to my zone that survive my winters with little or no protection. Hardiness often means the roots will survive even though there's severe dieback. On own root roses, this means the new growth will be true to the variety while the root stock of a grafted rose will often take over if there is severe die back.
The statement that "a grafted rose will be hardier than an own-root one" is not true.
I've found my less than hardy grafted roses are hardier when allowed to go own root. Not cane hardy, root hardy, and to me that's what counts.
I've seen grafted Willie Baffins and other minus 40 degree grafted Canadian Explorer and other cane hardy roses fail because of graft failure in winter.

An own root plant may die back to an inch or two or three underground (the part of the rose below that level is "insulated" by the soil and snow above that "freeze level"). But, the rose can still grow back "true" come spring. However, if it is a grafted plant and dies back below the graft, all you have left alive to grow back in the spring is understock.

Planting the grafted rose very deep may not solve the problem as the roots may be too deep to benefit from the water, oxygen, nutrients etc. needed for optimium growth.

Here is a link that might be useful: tree explanation for optimum root depth

I have to admit this is an issue that is very close to my own experience. I have been a gardener since a very young age, but it is only recently that I have begun gardening seriously with roses. The primary reason for this is that as a young man, and already experienced gardener, most of the roses I planted--grafted, as that was about all I could find back in the '70s--would die back during the winters and come back as the rootstock. After a few years of this I just gave up on roses as a bad investment and concentrated on other shrubs and perenials. It wasn't until the '90s that I heard much about own root and old roses, and by then I was going thru a series of moves that made long term gardening plans problematic. But since I have gotten back into roses, I have found that own-root are all I really feel I can trust. The first year of my current rose garden, I planted about 60 roses--40 own root and 20 grafted. Half of the grafted ones died, and only 2 of the others, over the course of the following months. So I would say, strictly from my own experience, that any rose is healthier and hardier on its on roots than on grafted ones. Yes, I know this is anecdotal evidence. And yes, I've heard the reasoning that some roses, such as Angel Face, are not vigorous enough on their own root and need the boost from a more vigorous rootstock. The problem for me personally with that is, Angel Face was one of those roses I tried to grow repeatedly back in the '70s, and a yard full of Dr. Hueys didn't really help me grow a more vigorous Angel Face.

Thank you for all the input. Here's the situation, I purchased an inexpensive "Intrigue" rose. I know this rose is not winter hardy for my zone and have read it is persnickety anyhow. I thought maybe taking a few cuttings and rooting them might be worth a try to see if an own root version might be an improvement over the grafted plant.

I, too, grow only own-root and have lost whatever grafts I've tried, regardless of vendor/quality. I have also lost own-roots that are not hardy in my garden. Many Hybrid Teas, Teas and Noisettes are too tender even for my 6b. Hardiness is in the genes and the reason so many roses are grafted is because they are not hardy. Sort of like sub-prime mortgages.

If you've planted grafted roses deep, how long would it take for them to grow their own roots?

The best way I know of to make a rose hardier is to make sure it's healthy going into winter.

Tough question and I haven't done the investigative work to verify my assumption. I have 2 grafted Hybrid Teas that appear to have own-root canes. I say 'appear' because I buried the graft on both, so without digging it up, I can't tell if it's a new cane from above the graft or if it's truly own-root. I suspect own-root because the new canes emerged over 12 inches away from where the graft is buried.

If they really are both own-root, it took them 3 years, and they were both big, 2nd-year potted roses when they were purchased & planted.

One recommendation that I have seen is to plant a grafted rose on an angle so that both the grafted roots and the exposed above graft cane are in the area where roots receive enough water and oxygen to grow. Then nature can decide which is better.

I have used both the above and the taking of cuttings which are then planted right next to the original plant method.

Planting the grafted rose on an angle works, they often go ownroot by just having the canes under ground.

In my experience roses are hardier when grafted. In my area roses on a hardier rootstock leaf out and start growing well earlier in spring than ownroots (at least some varieties). Healthy big plants tend survive better than the ones that struggle, maybe that is why.

There are some research showing that soil blend and certain ways of fertilizing makes hardier plants. There are patened soil blends to make plants grow better in more exposted situations. I know using seaweed and organic composts and fertilizers have in some cases have prooved to give less winter damage. It certainly is worth trying if you want to push zones. Don't apply a lot of nitrogen late in summer it will result in less hardy canes. If you are in a zone where snow cover comes before frost and the ground doesn't freeze grafted plants should be no problem, even an advantage. If the soil freeze it is horror for the ownroots too.

I agree with Seil.

A rose will acclimate itself to a zone, but giving it cover in winter that is thorough enough for probable survival without over prtectting is the only thing a person can really do.

One can take a chance, hoping the rose adjusts its habits, by uncovering a little earlier than normal and giving it temp. protection if need be but a rose is either hard-wired by God to adapt or it is not.

Has anyone tried FreezePruf?

The following link is to the original scientific publication abstract. I cannot get acess to the full paper over the internet, but I suspect that the product contains a silicate.

http://horttech.ashspublications.org/content/21/1/109.abstract

Here is a link that might be useful: FreezePruf review (not link above)

From the link below:

"Seaweed has also been found to increase plant hardiness and resistance to adverse environmental conditions, such as early frost, ....."

Any comments?

Here is a link that might be useful: link to commercial adv

Components in FreezePruf:

"What is it? FreezePruf is a mixture of several fairly common compounds. These include WiltPruf (a film-forming anti-transpirant), SilWet (a surfactant � helps material spread and stick to leaves), AgSil (potassium silicate), polyethylene glycol (an osmoticum - PEG is widely used in cosmetics and laxatives), and glycerol."

From Washington State Univ. link below.

Here is a link that might be useful: Washington State Univ. link

This appeared in the national "Science Daily".

Here is a link that might be useful: 2008 Science Daily News article