I don't know about grafts in general, but in our zone 6, we are in a transition area--50-50 chance that cold weather will harm the graft on a rose. Of course, even in Las Vegas, some people are frequently winners. Myself, when I gamble, I seem to lose!

Strictly speaking, I don't think it is actually the cold in and of itself that is the problem--but more the late-winter/early spring rising and lowering temperatures (though in recent years, that kinda describes our entire climate change winters here in my zone 6). When it warms up, tender new growth starts, then a late freeze comes and kills off the top of the plant. If that happens often enough, the rose can get too damaged to recover decently. Obviously, a strong healthy rose has a much better chance of surviving.

And some of it can be just pure unexplainable CHANCE. No rhyme or reason--it just happens. Hyper-sensitive rose growers tend to be devastated when something happens to their beautiful roses, regardless of the reason!

Burying the rose graft is no guarantee that the grafted rose will be fully protected. It just increases some of the odds in the rose's favor.

I fully intend to go on planting the grafts a couple inches below surface--though I have lots of non-grafted roses also.

Kate

Thanks but you just said everything I already know lol!

My point here is, am I being told that rose grafts are inherently different from the grafts of other plants (I noted that fruit trees, grape vines, etc have grafts which experience all that stuff you wrote but are always planted above ground and seem to do just fine)? Or is there something else I am missing?

I always assumed it had something to do with the inherent tenderness of the scion rose. I'd like to do some experimenting with hardy rose grafts, but until I learn to do it myself those roses are rare enough that I don't want to play around with them.

That's not how I read mad_gallica, my reading of what was said there is that the understanding is based on the need to protect the scion which is expected to be tender. But that does not work because we are encouraged to bury all grafts, so even in my zone 5b/6a area, when you have a rose with a hardy rootstock of Dr. Huey (hardy to zone 5) or even Multiflora (hardy to zone 4), and a scion like say Champlain (Hardy to zone 4), so then you have a graft that is rock solid hardy for my zone, yet I am still recommended to bury it.

But are you really recommended to bury a graft between two hardy roses?

The reality is that over the years I have run into very little rose advice that can't be described as Hybrid Tea advice. Most of it is rather humorously crazy. For example:

Roses don't like competition, so keep weeds and companion plants away.

Change this to

William Baffin doesn't like competition, so keep weeds and companion plants away.

I expect most people with personal experience of William Baffin understand that as a joke. But what about something that isn't obviously silly like burying bud unions? There isn't a big enough pool of knowledge out there to know.

If the rootstock is rock solid winter hardy in our zones and the scion material which is grafted onto it is also equal in winter hardiness, be it a rose, grape vine, apple tree, apricot tree, etc., they will survive our winters with no die back, neither the scion, the graft union, nor the root stock will die or be injured.

That is why you see grafted: grape vines, apple trees, peach trees, on and on down the list, thriving all around you where you live. All parts of these plants are winter hardy in your zone.

Now we come to roses.

Many of the most desirable roses (I'm using the hybrid tea as my example tender rose), are not winter hardy at all, or border line winter hardy, with some survivability in our zone. If our model hybrid tea is grafted onto a winter hardy root stock, which is the wise thing for growers to do if they want their grafted roses to live in our climate, partial success is achieved so far, but what about the tender hybrid tea scion material that they graft onto the winter hardy root stock?

In an attempt to keep the scion from dying completely or partially over winter, the bush is planted with the bud union below soil level. The depths at which the bud unions are positioned vary according to winter severity and soil types (sandy, clay, or rich topsoil); anywhere from 2 to 6 inches below the soil surface. The expectation is that if the bud/graft union is protected from the intensity of winter's cold, it will survive the winter. If the bud union is killed, it"s all over.

The bud union is as tender as the scion material (he hybrid tea canes growing from it). The bud union gets no winter hardiness from its winter hardy rootstock.

In warm climates the bud unions are planted 2" or higher from the ground. It is not necessary to protect bud unions since winter kill is not a factor. One positive reason the bud union is placed above ground in warm climates is that sunlight hitting the bud union stimulates basal cane production...the life blood of a rose bush.

The coldest temperature ice (frozen soil), can be is 32 degrees F. It can be no colder. It is the winter air temperature, not the frozen ground temperature of 32 degrees F. that kills roses. 17 degrees F. and lower kills rose canes of the hybrid tea types. 32 degrees F. Is safe for bud union survival. Actually even down to about 25 degrees is safe for bud union winter survival, but that's the limit.

The manner in which roses grow is regeneration of growth from the crown. An own root rose has a crown. A grafted rose has a crown also. It is the bud union. A grafted rose's bud union sprouts new basal growth, continuously renewing the bush. This bud union, if from the typical tender hybrid tea is also tender all its life long.

Hope I helped you.

Moses

Moses,

Your explanation left me wondering something: would it be beneficial to bury the bud union deep for the winter, but then to pull back the soil to expose it in the summer so it gets sunlight and stimulated growth? Or would that "bowl" in the soil cause problems?

mad_gallica, yes, the advise I've always read is that for us cold zoners (6 and below), we should bury the graft even if the scion is hardy and the rootstock is also hardy. You could be right that what we have there is a general hybrid tea advice being applied to everything. I just may pick up some $5 bodybag rose for which the scion is hardy here and plant it with the graft above ground and see how it does over a couple of winters.

If the graft between a hardy rootstock and a hardy scion is good to be exposed around here then perhaps I can stop hauling my hardy tree roses (like my double knock out tree rose) in every winter

P TW,

I think disturbing the soil to that depth may create problems. Your idea is very logical, though.

Very often when the bud union is planted below soil level, the top graft, scion, will start to grow its own roots. I think this root growth would be hindered or even be prevented if the soil was disturbed.

I say any more roots a rose can grow will only help it thrive.

Moses

P TW's idea is actually done by the most hardcore folks lol, I just don't have the time for that.

I've just come to accept one cane wonders as a part of growing grafted roses in this climate. Since the graft is buried in my clay soil, it never sends up new basals, so one cane wonders abound.

Richard, get a Polar Joy rose tree, it's very hardy (zone 4).