As we begin to move into the colder months here in Colorado, I’m hoping to get some advice on overwintering. For conifers (e.g., atlas cedar, nana, and hinoki) and deciduous (e.g., trident, acer, beech) trees that can stand up to colder temperatures, how much protection do folks generally provide? We live in the metro area and don’t have quite enough space for a greenhouse, but we do have a garage. I’ve also heard window wells can offer some protection (which we can make use of as well). Thank you in advance!
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Hey Stew:
Really great question. For the conifer and cold hardy species I'd put them on the ground and heel them in with mulch to the rim of the pot. Make sure they are out of both the direct sun and especially wind. In the weeks where we don't get snow you will need to check and water them. Many folks have a cold frame, which is an upgrade from this. Window well with mulch is similar to this, but you have to be able to monitor the watering. Caveat: if your trees are in SMALL containers.... you may want to bring them into the garage and watch h20 closely.
Deciducous stuff ideally should go in unheated garage with a bit of light. Watch the watering until you figure out which trees can tolerate the above treatment (maybe beech, but not maples).
Hope this helps. Could really be about an half an hour discussion.
Andy
Is it generally ok for the native conifers to get no direct or dappled sun in the winter, for instance heeling them into an area that is fully shaded all winter? Is the avoidance of sun mostly to keep the root mass from freezing and thawing frequently, or are there other considerations there? Thanks!
(Hope it is okay to revive this thread) I have a few possible areas I can heal in: (1) a long my eastern facing porch where there is a strip we have annuals growing -- basically just below where they've grown all summer on the ledge of the porch. (2) a planter facing east, but behind a Honey Locust, so it gets a bit more shade than option 1. (3) I can nestle them between a raised garden bed, a barrel of hops, and a fence in my backyard -- that would technically be south facing, but the hops barrel could block some southern sun, but this would probably offer the most wind protection.
Andy gave you some great advice. You do want to avoid the freeze and thaw cycles on your trees. Wind is your worst enemy as it will dry them out in a hurry and kill them depending on the species. Of the species you originally listed I would not keep any of them outside in Colorado and would put them in your garage. Conifers will do just fine in your garage with no light. Or you could put in a fluorescent light if you want. You can also use a seedling heating pad in a garage to keep roots warmer on trees that might be somewhat iffy or may be not well to help them survive the winter. Nursery container trees can be kept outside in a protected place out of the sun and set directly on the ground. Build a wall around the trees with bales of straw one bale high. Level the pots off and insulate the trees with fallen leaves shoved very tightly in between the pots and straw bales. Add leaves to the top of the pots. Remember to water these trees during the winter. This is only for cold hardy nursery stock. Does not apply to Cotoneaster, Sage, or Sage type plants. Be sure to move these trees out into sunlight when they break dormancy. Failure to do so will result in long leggy branches and probably die sometime latter. I have some other ideas and suggestions on my website you might find helpful here: https://rockymtnbonsai.com/index.php/bonsai-basics/winter-care/
Thank you all for the great insights here! I really appreciate it. In terms of timing, when do you all make the shift to heeling in your trees or moving them to a sheltered space? Do you wait for temps to drop to a consistent low (can they stay unprotected until we have longer periods of freezing temps)? I figured the trees should stay out for much of the fall, if possible.
It depends on the species. I generally have them all put away for the winter when the temps start to get into the single digits. I did move two thirds of my trees into the garage during the early snow fall. They are now all back out side and the tropicals are in the house until spring. Garage housed trees also present a problem in spring because some start to bud out way early. These trees will have to be moved outside during the day and back inside during the night time. Wise planning on your part will position these trees close to the front garage door instead of in the back of the garage making it difficult to get to them. Another thing to consider is to install some "small gravel" bunkers where you can simple sink your trees into it in the fall and not worry about timing it just right. I have left my bigger conifers buried in the gravel bunker all year. Watering trees in the garage is very important as they will dry out and die if not watered. Group trees that need more water together someplace you can get to them with out emptying out the whole garage to water them. Trees on heating pads will need a lot more water and will dry out quickly leading to death.
This really helps! Thank you so much for the guidance here!
I wanted to build off this question if I could.
What do we do with deep freezes ahead of the hibernation period? In Denver we are hitting single digits tonight and tomorrow and some deciduous trees haven't lost leaves, so I think it is safe to say they are still building sugars and preparing.
But to clarify - I'm thinking temperatures so low that there is a risk of freezing even if it were winter. I might be way off since I'm inexperienced...Maybe they are totally fine in the pre-winter drops.
Should trees be brought in from the external, unheated storage to prevent freeze or should they be subject to fluctuating temps?
Tree examples would be Acers, Junipers, and Cedars.
Yes bring them into the garage etc. then set them back outside after it warms up till they drop their leaves.
Right right, and I'm sorry if I wasn't clear, I mean from the garage into the apartment/home where it is 70f. My fear is too cold of weather while they are beginning to prepare for hibernation with us seeing single digits out of no where.
If their leaves were off and it was late December I would simply assume leave in unheated garage.
Thanks.
@Barlow Anderson I am a little confused, which is normal, outdoor Bonsai should not be going into your apartment at all. Put them in the garage even if they are fully leafed out. They will be ok for a few days until you can put them back out and let them drop their leaves. Sometimes it is not possible to put them back out to loose their leaves to, which means they will die off in the garage and the tree will be ok. The only trees to go into the apartment should be tropical trees.