Sudden frost effect on perennials...

musicalmommy(Canada 3)August 19, 2005

What happens to Perennials when there is a sudden frost when they haven't had a chance to go "dormant"? Are they killed? How much time does it take for them to go dormant?

In the Fall, what do people do with all the dead foliage? Do you cut it down to the ground...or will people understand if you leave the dead stuff there until the snow covers it. I would prefer to defer the work until Spring. I'm kind of "pooped" out with gardening chores :D What about my annuals in containers? Can I just leave the containers outside where they stand and cut off the dead stuff? Some containers are very heavy and I dread trying to empty them and lugging them into the garage for storage. Do I throw the dirt and dead plants into garbage bags for the dump? I would prefer to leave the containers where they are and cutting off the really visible dead foliage but I don't know if that is acceptable or will people think "eeww". All these years, I've never taken the time to notice what people do to their gardens/containers over winter. We have up to -30 celsius winters. Thanks so much!

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tapla (mid-MI z5b-6a)

Plants develop a pre-dormant state and begin to develop cold-hardiness primarily in response to the increasing periods of darkness as days grow shorter. Secondarily, but also important, exposure to increasing chill moves the plant closer dormancy and increases resistance to cold. How a hardy plant in your zone reacts to freezing temperatures depends on its physiological state at the time of exposure. E.g.: In your zone, a hard freeze on Aug 1 would find most plants actively growing & cause dieback to the ground in most herbaceous perennials. The same freeze on Sep 15th would still affect many plants, but some wouldn't be affected & others only marginally because the plants are in the process of preparing for a winter rest and developing a mechanism to cope with freezing temps. Of course, as temperatures later plummet, most of the non-woody material will die to the ground

I'm sure others will help with the remaining questions. Take care.


    Bookmark   August 20, 2005 at 1:19AM
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musicalmommy(Canada 3)

Yes, that makes sense to me. A few days ago,(mid August) it got to 2 degrees celsius, which is only 2 degrees above freezing. It is rather unusual for it to get so cold in August. So, I was worried about the plants being killed. They look like they survived... So, I guess you are saying it takes several weeks of gradual darkness and coldness for the plants to go dormant. is unpredictable around here. It often goes cold "suddenly". Today, we were in the high 20s and the weekend will be in the 30s. Imagine, a few days ago it was only 2 and near freezing temperatures. That is Canada. Thanks for the great science lesson. :)

    Bookmark   August 20, 2005 at 1:59AM
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pitimpinai(z6 Chicago)

I am an obsessive composter. I would put the extra soil in the garden and use the spent plants, kitchen scraps, etc. for my compost. Dumping them in a garbage bag seems a waste of perfect composting materials.

Composting does not have to be a big or elaborate operation. It is as easy as burying the scraps in the ground or put them in a pile or in my case,

1. I dug a trench between my flower beds, dump everything in and cover with cardboards or leaves or what not.
2. I also compost in garbage cans.
3. I make sheet compost/lasangna beds and plant on top of the compost.

It is really simple. And I live in the city.
Have fun. :-)

Here is a link that might be useful: Soil, Compost, Mulch FAQ

    Bookmark   August 20, 2005 at 8:30AM
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tapla (mid-MI z5b-6a)

It might also be interesting to know that plants don't necessarily have to freeze to suffer damage from cold. Many plants that have not hardened to the cold, and especially tender perennials (houseplants & perennials you grow as annuals in your zone), when exposed to sudden lowering of temperatures can leak organic compounds through cell walls. The effect in appearance is much the same as freeze damage, but can occur at temperatures well above freezing.


    Bookmark   August 20, 2005 at 10:34AM
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musicalmommy(Canada 3)

Yes, I had thought about composting but I didn't know I could do it without any elaborate set up. I can dig a trench and throw everything in there I guess.

As for my ceramic and clay containers, can I leave them where they are? Or, should I bring them into the garage. Some of them are super heavy. I don't want to move them unless I have to. Will the snow and freezing temperatures wreck them? I don't care if they develop cracks (or should I?). They would just be extra drainage holes. I just don't want them rendered useless.

    Bookmark   August 20, 2005 at 6:43PM
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vetivert8(NI-NZ zone 9a)

About the containers: many earthenware pots are labelled frost resistant. Others are not. Frosting can make them brittle. It acts on them just the way it does on rocks. Any tiny crack that holds moisture freezes, the ice expands, and bits flake off. After a while the pot starts to crumble. If there is soil in it, the soil expands with the frost and can cause the pot to break.

If the pots are very large then winter wrapping them could save you some hard work.

If you have them placed on a good concrete surface you can put them on plant trolleys to move them more easily under cover.

The annuals and their mix can be composted. If you want to reuse the pots clean them before you put them away. A dip into a chlorine bleach solution will also help to subdue any fungal spores that might have settled.

It's better to do this job around now. Dry mix is very nasty to work with. It's lovely to just go to a pile of clean pots and start immediately in spring. Bugs and things have nowhere to winter over.

If those pots are big enough, and you have the room/facilities - you can start bulbs indoors using pots, ready for planting out next year.

For winterising, ask on the Far North site: bubble wrap and frost cloth, heavy-duty insulation and string all come into it. A bit more serious than my haphazard 'chuck a bit of cardboard over'...

    Bookmark   August 20, 2005 at 10:40PM
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pitimpinai(z6 Chicago)

As to what I do with perennials in fall, if I need to clear the spots somewhat to tuck in some bulbs, I cut down the perennial foliage. I don't do that on the perennials that are
marginally hardy in my zone, leaving the foilage to help insulate the crown. I also add a pile of leaves around it around Christmas when the temperature drops. In your area, you might have to cover the plant earlier than Christmas. I don't normally mulch hardier perennials.

I urge you to start composting. It is the best way to improve your soil. It will keep a lot of good stuffs going to waste.

Here's my composting set up:
The compost in garbage cans sit on top of my trench compost. The plants on the right were planted on top of a sheet compost.

    Bookmark   August 20, 2005 at 11:55PM
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Skybird - z5, Denver, Colorado

If you decide to leave the pots outside over winter, the drier the soil is, the less likely they will be to crack. When I leave soil filled pots outside in winter, I lay them on their side--don't know why, but they seem less likely to crack---maybe it's because the soil stays drier.

    Bookmark   August 21, 2005 at 12:49AM
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musicalmommy(Canada 3)

Lots of fantastic advice. I've learned heaps. Thank you!

    Bookmark   August 23, 2005 at 12:49AM
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