On the subject of frosts ...

hi there, i thought I'd start a new topic since frosts have come up in a couple of topics..

unfortunately I am an aficionado of frosts as we get about 95 nights where the temperature dips below zero and about a quarter of those would be minus 5 or colder, and probably a dozen between -9 and -12 (our all time low was minus 15). Now it is true that the northern hemisphere literature on frosts doesn't apply to us.. but it is not because we don't get that cold in Australia (mind you, we know it gets much much colder in some places like Canada where it can be minus 40, but maybe they don't grow roses in those parts).. we differ with the northern hemisphere because we don't get long term insulation from snow but more because of the wild swings in temperature.. our day time temperatures during frost periods swings much more wildly than parts of the northern hemisphere.. so here on the northern tablelands of NSW we could go from minus 10 at night to 15 C in the day with brilliant sunshine.. so the plants get tricked into growing in those frost free intervals to only get checked back when a frost hits again.. this is why wrapping the plants in hessian (or burlap as they say in the northern hemisphere) doesn't really work here, because the new growth gets restricted..

before you all start wondering "why would anyone live on the Northern Tablelands", there are lots of great reasons and i am learning from this forum that maybe other parts of Australia have bigger problems with disease than we do..we actually get the majority of our rainfall in summer with moderate humidity so i am wondering whether black spot gets nuked by our winters..

now about 5 years ago i saw an advert in a gardening magazine for a product that the manufacturers claimed you could spray on your plants to prevent frosts from killing the plant.. maybe it wasn't a big seller as i haven't seen it since and i am annoyed with myself that i didn't buy any and will blame the fact that i didn't on my wild kids as they probably prevented me from following the ad through during spare time.. but.. did you know that lettuce leaves will freeze but thaw and look great whereas at the same temperature deficit the rose plant can die.. it has something to do with the white latex in the lettuce leaf .. now if we could trial that as a frost spray we could all be a lot happier..certainly this little black duck.. [my husband said we should angle for a GM rose with the Antarctic fish gene, that prevents this certain species of fish from freezing, to be spliced into the rose genome.. i just told him to go away]...soon i will stop talking about frosts, around about Melbourne cup day

well before i sign out i will just say what a beautiful day we have had here today and how lucky we are to live in this beautiful country,

hariet, I take my hat off to the amount of effort you put into researching ways to grow your roses under very testing conditions. If I lived on the Northern Tablelands, I’d never buy another book or spend my hours googling, I’d just do whatever you do.

The Beales guru mentioned a Canadian professor at one of the universities there who developed roses that are better suited for the harsh conditions there, creating a new class that was quite successful for a while. I’ve been looking for the reference for you, but cannot find it anymore, as I have forgotten the name, and can’t just go to the index. I came across it when reading the book cover to cover. If you like I let you know when I see the section, as I intend to read the book again.

we have had a few frosty nights down to about 1,2,3 degrees and I find that some of my new growth about 1-2cms long have turn brown and shrivelled up. Is this what they call freezer burn?

Hariet-rose, you are one dedicated rosarian! I can't imagine doing anything on such frosty mornings and chilly days but sit by a cosy fire and not emerge until the sun has some warmth to it. I must be part reptile! Your efforts and passion for your roses is truly admirable.

Hi all , been awol for a while . Interesting reading about your frost experiences Hariet . The product that you were referring to wasn't Yates "Stressgard" was it ?
We have had night after night of sub-zero temps here and absolutely beautiful days up to 20deg, but it is all starting to wear a bit thin as we are not getting our desperately needed rain and all the frosts are doing is drawing up the sub-surface moisture which freezes overnight and then evaporates away into the atmosphere when the sun gets up next morning.
Haven't noticed any frost damage on the roses that have been pruned though , but oh my poor jacarandah .... I don't think I will get many flowers there this year

Jackie, I think the nam,e of the roses from Canada are listed as 'Morden', memory tells me it is named after the research centre where they were/are bred.

American Rose Annual 28: 95-99 (1943)
How Frost Damage Occurs
CONTINUED ROSE RESEARCH AT CORNELL
By DR. R. C. ALLEN and GEORGE N. ASAI
Department of Floriculture and Ornamental Horticulture, New York State
College of Agriculture, Cornell University, Ithaca, N.Y.

Observations on the plants were made after each cold period. On December 8 the minimum temperature reached 4°F. No injury was noted in any of the test varieties.

By December 12 the minimum temperature had dropped to -1°F. Some injury was noted in the pith and inner portions of the xylem in Radio and Radiance, and in the upper portions of the canes of Frau Karl Druschki. However, when these plants were transplanted to the greenhouse they grew normally, indicating that the injury observed was not great enough to impair the subsequent growth.

On January 6 the minimum temperature reached -20°F., and it was noted that all portions of the canes above ground of the varieties Radio, Radiance and Frau Karl Druschki were killed. The upper half of the canes of Dorothy Perkins were killed, but the lower half recovered and produced somewhat abnormal growth. Examination showed that pith, xylem rays, inner cortex and pericycle were seriously injured. Some injury to the pith was noted in Ames No. 6 and Rosa multiflora.

It appears that the injury from severe freezing depends largely upon the minimum temperature reached. Other factors which were observed to exert some effect and are being studied further were the rate of freezing, the length of the period of minimum temperature and the degree of hardening which the plants have undergone. Thus it is not possible to predict accurately the degree of injury to a given variety from the minimum temperature alone.

With these temperatures(4 F is -16C, -1F is -18C and -20 F is -29C)
it is pretty rare that we would experience these in Australia. Hydration is also an important factor in frost protection, if we are going to have a severe frost I always make sure the soil is quite moist if not, I water, yes even in winter.

Warren, can that cause 'irradiation' I think that is the word for drawing water/moisture from the soil when it warms up above the soils surface

Just to add some nice info, it is -3.5 at present

As the frost forms ice crystals it draws moisture from the subsoil and when it warms up the moisture evaporates into the atmosphere.

-3.5C why the shivvering icon, I was snow skiing in the French Alps one year, over 3,000 metres and it was -45 C. I am glad nature didn't call LOL

At our place we'd never really had bad frosts except for the paddocks "down on the flats". That was until about 2006-2007 when the drought was several years in and the frosts just drew the moisture out night after night.
It was always interesting to note that often there was more frost on the mulch than on the bare grass.

But talking about colder temps -- when I visited my friends in Canada (where they know about REALLY cold weather... brrrr) I managed to snap a pic of their wild Alberta Rose.
This pic was taken as we headed off into the Rocky Mountains.
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Anyone that climbs to 3000 m and then skis down is nuts anyway, no wonder it was -45.
that Alberta rose is lovely Wendy, but isn't Alberta a minus temperature place as well

Yup. Easily gets to -40C in winter. (In the area that the roses were in.) Very short growing season too.

Dave this has nothing to do with roses but this is one of the places where I skiied when in France, Saulire in Courcheval.

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the hills are alive with the sound of snowwwwing..........[You must be registered and logged in to see this image.]

David, I can’t find it in the index – no idea where I saw it; and I only just read the book, how sad is that?
But Morden Nurseries, Canada is listed in the appendix, so you’re absolutely correct; thanks for putting me out of my misery where I’m thinking I dreamed it (gee, RTA makes you stay up late). They would have a webpage with lots of relevant information to follow up on.

They also have a line of roses named "Morden ----"

And that must be the ones I read about, under whatever heading …