Hi,

My first frost often occurs in very late November. As a result, for example, if the roses receive a food that is designed to last three months, it is given in late August, 3 months prior to the projected frost date. I do not want to do anything to encourage growth when it becomes cold, so nothing after that August feeding in this example, except for water as needed, because we still have to water here but infrequently .

Lynn

Most once-blooming roses are deciduous and will go dormant and drop their leaves regardless of what you do. This is in response to changes in the light. On the other hand, repeat-blooming roses are naturally evergreen and will not drop their leaves in response to seasonal change, but only after they are killed by very cold temperatures. disease, or old age. These roses will become semi-dormant when the soil temperature and the average air temperature stays below 4 degrees C. They may grow out during warm spells, and then the new growth will be killed by temperatures below -2 C. As long as these hard frosts occur every few weeks, these roses will not be able to make significant growth; however, they are not in true dormancy. Also, we cannot make them go dormant. Only cold temperatures can do that.

If you expect the weather to allow your roses to grow and bloom through the winter, then you should keep fertilizing through fall and winter, but at a reduced rate. Otherwise, you should stop fertilizing 5 or 6 weeks before you expect them to stop growing and blooming. Plants cannot use fertilizer unless they have undamaged leaves that are actively doing photosynthesis. When fertilizer is applied at a time it cannot be used, some of the nutrients will be wasted by leaching into the deep soil, which is a form of pollution.

Thank you Lynn & Michael,

This is so interesting! Why is there a difference between the once blooming roses and the repeat bloomers in terms of deciduous vs. evergreen?
It's like the repeat bloomers have mini generators in the basement?
And I guess the real question is what is "dormancy" exactly? What is "semi-dormancy"?
Michael I feel like you can explain the science... Please help?

So if I understood you correctly, for the repeat bloomers, the feeding, if not used up before the plant goes "semi-dormant" when the temps reach -4C, then this excess doesn't harm the plant in any way, but is just wasted?
When you say "pollution" do you mean harmful or wasteful?

One more question... When the hard frosts and consistently low temperatures come along and the roses are bare, is something happening at root-level? Growth? Or nothing at all?

Thanks!!
Annalyssa

1. Why is there a difference? Most species roses are from the temperate zone, ranging far north where they need true dormancy to survive the winter. Being deciduous allows them to remove and store nutrients from the leaves before dropping them. But modern roses get the repeat-blooming quality mostly from R. chinensis, a sub-tropical species that is evergreen in its natural habitat, growing and blooming all year. When these roses are planted where the temperature falls to -12 or -14 C, they can suffer severe damage from the cold.

2. In full deciduous dormancy, roses load their stems with antifreeze, drop their leaves, and shut down until mid-spring. In semi-dormancy, roses have stopped growing because of drought or cold damage, but they will start growing again whenever conditions temporarily improve.

3. Waste nutrients can be harmful pollution when nitrates leach down into the water table, which can make water unfit for drinking, or when phosphate-laden soil particles wash into surface water, where they can over-fertilize a lake and cause algae blooms, etc. Also with useless fertilizing, we are wasting non-renewable resources.

4. Gardeners speak of root growth during winter, but actually nothing much happens once the soil temperature falls to around 3 C. Also plants are not taking up significant amounts of nutrients unless photosynthesis is happening and healthy leaves are pumping water up through the plant.

Feeding....now. Are you insane - this is the time for slacking off....until May at the very least.

I'm nervous about using chemical fertilizer more than once a year,in spring; I'm worried that it might poison my already deprived soil,plus it has to be watered in, and I don't have access to running water in my garden,and finally, it's pretty expensive. I'm busy adding organic matter to my soil now,figuring that the nutrients will break down slowly, and the plants can use them whenever they need them. One of the gentlemen at Rose Barni, in fact, advised that autumn is the best time for top-dressing with manure,because if it's done in spring it breaks down too fast! but this is here in Italy...bart

Michael, thank you! That makes sense.
So, for example, Albas, gallicas, centifolias, these are truly deciduous, while all those bred by crossing with r. chinensis (bourbons, portlands, hybrid teas etc.) will be in some form only semi-deciduous because they've retained the evergreen gene to some extent?
Now does this mean they don't at all act like deciduous plants (don't form an abscission layer at the leaf base, don't store carbon and nitrogen before dropping the leaves - ok I looked up "deciduous") or only partly?
And is Roxburghii Plena also one of these evergreen species?

This morning I walked past where I just planted "Old Blush" (chinensis), "Roxburghii Plena" (roxburghii), "Jacques Cartier" (Portland) and Rose de Rescht (damask?) and I now see four very different animals!

Thanks!
Annalyssa

This post was edited by Annalyssa on Sun, Oct 20, 13 at 6:13

Hi bart!
Where are you in Italy? I'm assuming nearby since you've paid a visit to Barni!
I'm hesitant to feed my roses chemical fertilizer at all!
I still haven't had our soil tested and am scared to add anything in large doses. I don't want to play God unless I'm sure I know what I'm doing... If you know what I mean...
Even though I feel like no matter how much you know about your soil there are so many factors, it's practically impossible to take everything into consideration.
So for now since I'm just a beginner I'm going pretty light on the feeding, on the pruning, on the spraying, on everything. And my father in law is not allowed to touch anything! :)
I'm kind of just watching.
Maybe this means i'll have sad bloomless plants for a while...

Oh and I have a question you might be able to answer but i'll post in another thread...

:)
Annalyssa

Annalysa,

I assumed that your soil was properly amended and you were referring to chemical feeding. In August I revitalize the soil for roses with organics or in the past have used a granular fertilizer on established roses. After this feeding, nothing is done except for the addition of mulch, but I have been amending this soil for close to three years; twice annually, and some areas at least had compost that was added previously. Protocols in different regions vary, and you wrote that your temperatures are already in the teens for the low, 22 for the high, so, it is already cold where you are. I know in many regions here, when it becomes cold, people just make sure their roses are protected if they are a variety with that need, and let them be until sometime in the Spring.

I simplified to a bright line between once-blooming and repeating, but there are intermediate cases. Banksias are onece-blooming but tender. Rugosas are deciduous but bloom some throughout the season. Ditto for repeating damasks. Some of the complex 19th-century hybrids have only some of the China characteristics, so they are partial repeaters but hardier than hybrid teas.