I bury mine 4-6 inches deep. The underground temperature isn't much different 2-6 inches below the surface. While the surface temp may get well below zero, underground, even if frozen solid is close to the freezing point of 32 degrees and stays that way. Depending on your hardiness zone it's very likely the soil won't freeze a foot underground.
Keep in mind, the feeder roots grow in the top 6 inches of soil. Until the canes buried under the surface grow feeder roots in this portion of soil, your bush may not do well or could possibly not survive. Roots need oxygen to survive. Burying that deep could cut off the supply of air which is brought down by water.
If they seem to be growing Ok, they've probably gone own root already. In the future I'd not go that deep and stay in the 4-6 inch range.

I agree with Karl. They don't need to be a foot down. Depending on your zone (which you don't give) you might go 6 to 8 inches but I wouldn't go deeper than that.

Yes, there are some varieties that do better as grafted plants. On their own roots they are less vigorous growers and may never be as large or bloom as much that way. A lot of the roses (hybrid teas in particular) bred during the 1940s to 1970s say were really bred to be grafted. That's not to say that all of those roses won't grow own root but some of them just do better that way.

When I look at fields plowed in the spring you can see that the ground's frozen a foot down, for what that's worth.

Do feeder roots mean ones that take up things other than water? Or what I mean is, what are the roots lower than six inches doing? or aren't there very many?

As I said on my accidental repost above, I'm hoping to dig up some of the stems as little ownroots because I haven't been able to root rose cuttings any good, so I was thinking planting them deep would help that too.

Here in Tuscany, Italy, the climate is quite warm, though winters can be tough:dank and wet,with lots of enormous temperature swings from warm to cold. So my climate is very different; please keep this is mind when reading this my contribution.
I think one can definitely plant roses too deep! I've planted mine deep, only to have the stems rot at the bases. Now I try to plant them with the graft only a little bit below soil level,preferably with a sort of "dish" around them that is a BIT lower than the level of the surface of the garden,which I can fill in later with soil once the rose has gotten established.Are you sure that it's really such a problem if the rose's roots are in soil that freezes? Because I get the idea that the worst thing for roses is repeated thawing-the-freezing-then thawing. Plus, I think it was Paul Zimmerman who said that roses hate cold wind more than just low temperatures...Just my 2 cents. regards, bart

Freezing has little or nothing to do with it, just as visible frost and snow have nothing to do with stem damage. To my knowledge there is no part of any garden rose that is damaged by temperatures of 30 or 32 degrees F. Very fine roots might be broken by frost heave (expansion of frozen soil), but these regrow quickly in oxygenated soil near the surface..

Freezing temps of 32 degrees F will not hurt roses. Winter kill comes from much colder conditions, and usually very dry ones to boot. While I was still living in NorCA we had an extreme cold blast (we call 'em Alberta Clippers on the west coast) that dropped temps at my house from a normal winter low of 28F, to three nights at 19F. That was in Sunset Zone 17/USDA 9, mind you, and within a quarter mile of the San Francisco Bay. Farther from the Bay it was much colder, gardening clients reported lows of 15F. Everyone plants roses with the graft union above ground there, to detect suckers more easily, and no one's heard of winter protection - you don't need it at 28 degrees F.

It was amazing - everyone's roses were spectacular that spring. No damage at all - none - and they all bloomed like never before that spring. Along with a lot of other plants, I recall the evergreen pears and the camellias were all spectacular as well. So you see, it has to be pretty darn cold to damage roses. This cold snap was at the time the 4th most expensive natural disaster in California history, due to shattered pipes, frozen landscaping and hort crops; the orange crop was destroyed and entire towns put out of work as a result. But roses were not affected at all.

Yes your soil might freeze to a foot down, but as karl said, it's still not all that cold, usually pretty close to 32 degrees and we know that temp doesn't hurt roses. Now someone from zone 3 in Alberta might have different experiences, frozen soil surface nearer the air might well get much colder there, but there's Canadian gardeners on this forum who leave their roses in the ground all winter, and they're not planting as deep as you are.

Most roots of most woody plants, roses included, are within the top 18" of soil. Anchor roots can and do go deeper but it's not to escape freezing. The zone of most biological activity, which includes plant roots, is within a few inches of the surface, where the air is. Roots and everything else need oxygen diffusing in from the air. Being frozen in winter is normal. It's a very good question though! I hadn't really thought about it before, if it were bad to go deeper (aside from too much work).

I should clarify may post above to say that that damage to the buried graft won 't occur unless the soil in that zone cools to well below 32 degrees. That's why the freezing point of water is irrelevant.

Most rose canes don't show any damage until temps get under 28 degrees. Which would be considered a hard freeze. Mine didn't even blink at 32 and a dusting of frost the other day. They're still blooming, silly things. I don't know about below ground. I'm thinking it would have to be even lower than that to damage the roots though.

I've read conflicting instructions - to bury grafted/bud unions to protect them, but also *not* to bury them, as it may encourage canes to grow from the host plant.
Which is best?

It all depends on what zone you live in.

Keep it simple. If you are in Zone 6 like I am, always bury your graft an inch or two. If you are in a colder zone, bury the graft 4-6 inches. If you are in a warmer zone, leave the graft at soil line or higher.

There, that's all you need to know.

Burying the graft has never caused my grafted rose to sucker from the roots, if that is what you are asking. If the rose froze hard below the graft and therefore the top half of the plant died, yes, the rootstock would likely start putting out cane growth. But if you follow the simple directions I indicated, it is highly unlikely you will freeze the top half of the plant to death. Therefore, you don't need to worry about suckers from the roots.

Oh yes, it helps if you buy roses that are hardy to Zone 6 (in your case). If it is only hardy to Zone 7, the top half of the rose probably will freeze to death. Some gardeners go to extreme lengths to winter-protect their "tender" roses (not hardy to Zone 6)--they call that zone-stretching. Sounds like too much work to me. I'd rather just buy the hardier roses and not have to worry about such things.

Kate

I planted my first order from Palatine and had the roots rot in deep clay while the upper areas survived. Part of this was multiflora in alkaline conditions. Now I put the long roots in a 15 gallon can and get no rot at all. The potting mix is very light and full of air. If I was going to plant long roots in the ground, I would place them on a slant or spread them out if I could do it without breaking them.

I have put roses deeper down to encourage own rooting on the stems and if I dig them out again a year later to make several plants, I find that the roots from lowest areas have rotted away in the bottom of the hole.

In theory you can plant them a foot deep but it depends on the soil. The better the soil, the deeper and stronger the root system. The fine hair roots can be deep as well if the soil is very rich. Here in SoCal my grafts are at least two inches down but after a few years of soil building they will be 10 inches or more. I've dug up roses where the original graft which is almost unrecognizable is one to two feet down.

The deeper down in the soil the less oxygen there is. Plant roots need oxygen as well as water and nutrients.

Help!A 86 year old friend of mine planted Knock Outs on either side of her side walk in Galveston about 2 years ago ,they bloom and bloom but she planted them to deep in horrible soil,no mulch..I want to try to spruce up those beds for her.Should I add some rose soil or just mulch?They are literally down in holes ,maybe 6 to 8 inches deep..Should I maybe level out the soil around them and try to mix in the rose soil and maybe top with good compost ,then mulch..Thanks for any advise!!

kg, sorry for butting in on your question, but I'll forget mine if I don't ask it right away. In re-reading this post, I see that kittymoonbeam plants her multiflora in large pots in the ground since she has alkali soil. Does anyone else do the same? There are many plants I'd like only available on multiflora and I always assumed I couldn't grow them, but this idea might work.

KG, do you mean the friend's roses have a "sinkhole" around them? Are the roots exposed? Can you post a pic?

Sinkhole is about right,I could see some roots.wish I had a photo but I’m about 65 miles away.Planned on going Valentine Day ,since that’s the day here in Houston we do our rose pruning

In that case, I don't see any problem adding more soil and mulching, but let's see what others say. You're a good friend.

1. I have read cold weather gardening books that actually did recommend planting the entire bush, upright, underground and fully expecting growth above ground to die every winter. What a lot of digging! Planting a rose on it's side, underground but less deep, makes a certain amount of sense to me to save more top growth (esp with grafted roses) without burying it every winter, like the Minnesota tip technique recommends. All this makes me tired. I'm so glad I moved warm!
2. I don't know why I got the numbers!

Karl, thank you for the hardiness zone finder link. What a pleasant surprise. I jumped a zone higher. So, when I thought I was zone stretching, I wasn't stretching quite as far as I thought.

My experience in my garden in Tuscany, Italy, about a zone 8, is that in warm zones you should definitely NOT PLANT DEEPLY, just bury the graft union bud slightly under soil level. In cold areas it's a diffferent story.