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rubyhum

Container gardening trees in winter

rubyhum
9 years ago

I have these baby trees in pretty large (22") wood containers. The Chocolate Mimosa and the Royal Star are the smallest plants, about 18" tall twigs.

Royal Star Magnolia
Chocolate Mimosa
Magnolia Ann
Regular Albizia Julibrissin

I read that hardiness zone is diminished by two zones when container grown, is this correct? Can anyone provide some tips on how I can overwinter them in Zone 6 NY? I don't have an unheated garage so I can't overwinter them indoors. Can I wrap them in some layers of cardboard and maybe a blue tarp and black garbage bags while leaving the tops open for ventilation? How about using some hay? I really want these to live. Any advice on this would be much appreciated.

Comments (8)

  • Toronado3800 Zone 6 St Louis
    9 years ago

    I do believe hardiness zones are diminished when container grown.

    Pack the containers in close to a building and then try to keep the sun off them. Hay might be great at temperature moderation and keeping the sun off the pots. I don't roll in it often. Any moisture issues?

    Is Albizia Julibrissin in all its forms invasive in your state?

  • gardengal48 (PNW Z8/9)
    9 years ago

    The primary concern is root damage. Roots tend to be far more vulnerable to cold temperatures than top growth, even with plants fully hardy for your zone, and containered plants are at risk because they do not have the insulating factor of all that soil mass around the root system.

    But 22" boxes are pretty good size! I wouldn't even think twice about them being fine in winter without any attention in my area but then we don't often get extended cold periods where freezing of container soil is an issue.

    The suggestions to group the boxes together is good - they will help to insulate each other. And locating them somewhere that might offer a little more protection is advised also.........against a south facing wall, in an alcove or "L" that the house may offer, a covered breezeway, etc. Out of direct wind, as that can have a cooling, drying effect on container soils that can increase freeze risk.

    When temperatures are predicted to get below freezing for an extended period is when you may need to offer some additional protection. Bubble wrap is great - wrap around all the boxes grouped together. Or space blankets. Or even stacking small straw bales (around now for harvest decor - you may want to stock up) around the base of the boxes.. If really nasty cold weather, you can gently drape the tops with an old sheet, blanket or burlap but no plastic. And remove the topping as soon as possible - it's the roots that are the concern.

    ps. I garden almost exclusively in containers :-)

  • ken_adrian Adrian MI cold Z5
    9 years ago

    can we see some pix??

    18 inchers would be easiest.. just healed in mother earth ... repot in spring ...

    i dont understand how big the ones are in the wood crate ...;

    i would be very leery of any plastic ... it can either trap too much heat ... or it might not breath ...

    the star mag went wonderfully thru a z4 winter for me last year ...

    my biggest concern in z5MI .. is too much water going in the top of a pot .. when the pot is frozen solid ... i might think about a piece of Styrofoam to cover the top.. with a cut out to get it around the tree ... thereby blocking a lot of water coming in the top ...

    how much snow cover in your NY area??? if deep and consistent thru winter... you couldnt just tip the pots over.. and let them get buried by snow.. one of ma natures best insulators ...

    but do insure.. the pots themselves.. stay out of as much sun as possible ....

    ken

  • hairmetal4ever
    9 years ago

    The bigger the container, the better.

    Ken makes good points about the water issue. I've been successful (although I'm z7 so it's less a concern) by piling shredded leaves around the pots to simulate the insulating effects of having soil around the rootballs, but that doesn't solve the drainage/water issue. Tipping them on the side (once fully dormant) can work in a SMALL container (5 gal or less) then covering with leaves or mulch.

    Heeling in is also good.

    However, that large of a container may not freeze solid enough to pose a threat.

  • ken_adrian Adrian MI cold Z5
    9 years ago

    in the large pot.. the issue is the media ... and how IT will take winter ...

    a variable which is hard to predict ... especially if its dirt ... rather than media ...

    just keep in mind.. a dormant tree doesnt really need all that much MOISTURE ... and it definitely does not need to be WET .... i am using different words to make the point ... and that was why i was thinking.. with a large pot.. to cover the soil surface if there is NO other option ...

    but do not let the soil get bone dry ... up here in the north... we would put a snowball or ice cubes on the soil every now and then .. and if it warms a bit.. it will melt and add just a little moisture ... rather than using a watering can and drowning the thing due to drainage issues .. some how or another ...

    in snow country... winter is almost a desert ... because all the water is tied up in a frozen state ... and the winter winds can desiccate media and foliage and roots ... and though we dont want to water a frozen pot.. we still have to be sure.. it does not completely dry .... this obviously changes every zone warmer you get ...

    ken

  • rubyhum
    Original Author
    9 years ago

    There's a lot of good info provided here, thank you all. I think it's time for me to buy some hay. Or bubble wrap. Whichever is more economical. Maybe hay will go on sale. I guess I could use it as a mulch or compost later in the year too.

    Ken, I don't have a picture but I can tell you it's not a pretty sight right now. Imagine a mishmash barricade and containers huddled together against a wall. If my plants make it through winter, the eyesore will be worth it.

    That's good news about the Star Magnolia. Why stay out of the sun though? Wouldn't sun help keep the pots from getting too cold? We rarely have snow blankets. No leaves either but I put some mulch on there for now, not on the trunk bark though.

    Agreed: I'm definitely going to have to monitor the moisture level diligently. There may eventually be a danger of too much water coming in from the top. Where to get Styrofoam? What a headache, I mean wonderful challenge container gardening is lol.

  • gardengal48 (PNW Z8/9)
    9 years ago

    I am not convinced that leaving in sun will be much of an issue. 22" boxes are BIG containers - they should hold somewhere around 3.5 cubic feet of soil (maybe more depending on depth). It's very unlikely that much of a soil mass will be influenced much by weak winter sun for a few daylight hours. Generally, the concern is more with black plastic nursery pots, which tend to be smaller as well as absorb heat more readily than wood. And sun or reflected heat can help the container soil from freezing solid, which is essentially what you are trying to avoid. As long as air temperatures remain cold, there is minimal chance of the trees beginning to emerge from dormancy too early.

    There may be an issue of sunscald on the more delicate stem tissue of the trees themselves and that may be something to guard against. Just wrapping the trunks loosely in burlap can help with that.

    I also have a hard time understanding issues exposing the containers to rainfall. I live in the PNW -- we are well-known for considerable winter rainfall. Rain pretty much starts now and doesn't really stop until April :-) I have never protected my containered trees and shrubs from this occurrence. As long as the soil mix in the boxes is properly fast draining (as ALL container soil should be), there is little concern. In fact, many of my containered plants fair better than those inground where winter soil remains quite saturated and I definitely prefer to keep plants of questionable hardiness and that require sharp drainage in containers rather than in the ground for this reason.

    And I provide no other particular protection unless we are predicted to receive one of our winter "arctic blasts" that will bring temps plummeting below freezing for an extended period.

  • rubyhum
    Original Author
    9 years ago

    gardengal48 "As long as the soil mix in the boxes is properly fast draining (as ALL container soil should be), there is little concern."

    This is wherein I think my problem will be. Time will tell. It's mostly potting mix with extra perlite added and a bit of compost. Are they doomed? In one pot I experimented with potting soil specific to cactus hoping that would be really good drainage. The odd thing to me is that the ingredients were the same as regular potting soil from what I can remember.

    May I ask what you use and if it is always the same exact mix or is there room for error?