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Frost / dormancy

Posted by purpleinopp 8b AL (My Page) on
Tue, Sep 25, 12 at 11:29

It was asked in another thread about which plants can handle a frost or two before coming inside, and which plants might even benefit from it, maybe be inspired to flower. I don't know if I have any plants that can be frosted without defoliating, which I think would be the deciding factor, so look forward to whatever experiences have been had.

About defoliation, it seems like the beginning of winter is a bad time to allow defoliation if one doesn't have a (cooler/darker?) place where dormancy could be maintained. Some people have greenhouses, so that's great, but if you don't... Won't they be confused trying to grow renewed "spring foliage" at the beginning of winter? It seems best not to induce dormancy in a plant if it's going to live in a fairly warm, sunny spot all winter, but that's just a hunch.

The only plant I have that seems to go dormant anyway is Persian shield. I've never brought one inside that didn't soon drop most of its' foliage.

I've decided to leave stuff like sweet potato vine, most of the T. zebrina, Tahitian bridal veil (Gibasis geniculata,) Datura outside where they won't be taking up space inside, but will have to grow back from the roots in the spring.

This also reminds me, my Mom has been saying for years that a lot of plants will be OK in frost if they thaw before the sun hits them. Like the rapid thaw is what actually does them in. It's not an easy thing to experiment with, but after watching things on those few special fall days for a few years, I think she's right. Plants on the west side of the house or in AM shade from a tree, in general, retain their foliage a bit longer.

I'm more confused than I was when I started writing this. oops!


Follow-Up Postings:

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RE: Frost / dormancy

Purple, thanks for starting this thread.

I've asked myself this question for years. Moreso, when it was said Jades need a cooling period for vivid coloring.
The only problem is, what's the lowest temps Jades thrive without freezing???

Thanksgiving Cactus and Kalanchoes bud when outdoors until first/second frost, and/or 32F, without leaf drop.
But, I wonder if foliage would remain on other plants, once brought indoors, placed in a cool, brightly lit room?

IMO, thin leaf, sub/tropials can/tend to drop leaves when left outdoors during cool/cold temps, then brought indoors. Certain Euphorbias, Ficus and Citrus are notorius for leaf drop after moving from one room to another, let alone bringing inside a warm house with lower light.

How big is your Persian Shield..I love PS colors.

What a difference between your zone and mine. Zebrina, SPV and TVB would be history if left out during winter. Datura is the only plant that grows and grows and grows, then come spring, sprouts..Everywhere. lol.

Love the last line of your post..lol. Toni


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RE: Frost / dormancy

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Tue, Sep 25, 12 at 15:40

I think this is a topic that leaves so much room for musing that you could end up holding onto your own tail & not even realize it. I guess I don't place near the value on experience that most people do, but in this case, next to good old fashioned research I think experience is probably the best teacher ...... and a deceiver as well.

First, the deceiver part - over the years, I've seen a lot of growers swear that their Ficus, scheffleras, dracaenas, and a long list of other plants are 'just fine - unaffected', left out in temps barely above freezing. They reach that conclusion because they are being deceived. The plant LOOKS fine, but what isn't being taken into account is the fact that at temps much below 55*, most photosynthesis has ground to a halt for houseplants, and the plant has switched over to battery power. IOW, the plant isn't relying on current photosynthate to provide the fuel necessary to keep the plant's systems orderly, it's relying on energy reserves. This means the plant is using more energy than it is producing, which means the plant is dying a little every day - so it's NOT 'just fine or unaffected'. The question most but not all cases ends up being, how much do I want to allow the plant to tolerate?

Experience and/or research comes to play when we're dealing with those plants that like to be tickled by a little frost or heavy chill to convince them they'd better start thinking about the future and set some buds so their genes don't get lost in the shuffle.

I have a lot of plants that I over-winter indoors, yet they don't seem to mind a little frost in the fall. Most of them, for me, are woody plants, like rosemary, Santolina, Eugenia, Luma (apiculata), Serissa, some boxwoods, but a lot of succulents don't seem to mind being left out during the first light frosts before being rescued to a more favorable clime.

Some plants concentrate solutes, like sugar/starches/oils/proteins in cells that act as antifreeze, which is why leaf cells in evergreens can withstand such low temperatures without leaves dying and how the cells in cambial and root tissues can often remain unfrozen even at temperatures as low as 0*F. So freezing temperatures don't always mean frozen intra-cellular water. When the water in cells DOES freeze, it kills the cells. Chill injury is different than freezing injury. Quickly falling temperatures can cause the leakage of certain biocompounds from cells in some plants. This 'chill injury' can closely mimic freezing injury, but can occur at temperatures as high as 50*, so there is THAT to consider as well. Chill can virtually STOP photosynthesis and the flow of auxin across abscission zones. This can cause an abscission layer to form and leaves to fall with no notable damage to the foliage of SOME plants - definitely NOT something you want to see happening to a houseplant From Aug-Jun.

All in all, there is a LOT to consider when it comes to trying to determine what is good or bad for a plant, what kind of cold we should/shouldn't expose a plant to, how much trust we should place in our own observations in this area, whether we are transposing what a plant will tolerate for what is in the plant's best interest, and I just bumped into myself coming around that last corner.


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RE: Frost / dormancy

Hi
I live in s. florida so have the opposite problem.lol There are many plants that REQUIRE a cool/cold rest period . Generally you can get an idea of what a plant needs by its origin. If from the "tropics"
Whatever the parameters experienced in the "wild" are generally absolutely necessary in culture also. be warned that there is GREAT variation within the tropics due to altitude . generally I've found "cool adapted plants MUCH more sensitive to heat than those that like heat are to cold. I have found MANY tropical plants that seem invigorated by 'cool downs " some go into a nose dive at 45 lol. I grow plants rated at 60 for a low and have yet to find one that won't survive lower temps . While I'm sure it doesn't kill them feel certain there is a "stress " factor. About all you can do is use you own judgement?? gary


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