Winterizing Chinese Elm

Nancy

Hi, am entering my first year with an outdoor tree! Yikes! Here in NJ, the weather has been "too kind." (Our magnolia in the backyard is budding.) My bonsai Chinese Elm is quite small and has an exposed root type style. So I keep protecting it, including the pot, which gets SO cold to the touch! I have kept the tree out of the direct sun. I'm trying to help it get a GRADUAL winterizing experience. At least it has quit putting out new growth. But it is not dropping leaves at all. They are still green. I know that at some point I will be placing it in a cardboard box with packing, for dormancy. The dormancy will be spent on my back porch, which is unheated. If I understand correctly, it will be in the dark and will experience lows temps., but not be allowed to actually freeze. Just will keep roots moist. What I feel unsure about, is WHEN exactly to box it up. When will it drop its leaves? What if we get a hard freeze? Am I baby-ing it too much? Just feeling doubtful. Real pretty tree that I love and don't want to kill.... thanks, Nancy

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mgc

From what I have read, Chinese Elms are hardy and are particularly frost-hardy. That may explain it not having dropped its leaves yet.
As for the rest, I'd say put it in a box now, keep doing all the other things you've been doing, and worry less.

tb2776

I'm in Flemington and I have a Chinese elm as well and it hasn't dropped any leaves; in fact, the leaves are pretty much green and lush looking.

I'm keeping mine in my unheated garage. It has a panel of windows that face the southeast so some sun does get into the garage. I didn't want to leave it out at night (night time temps were 24-28 degrees Fahrenheit this past week).

I'm just keeping roots somewhat moist -- not too much as I want the tree to start pushing out all that water and getting itself ready for dormancy.

Good luck and keep us posted.

--Tony

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Greetings from Flemington, NJ
Zone 6

lordy611

Here in central Maryland I have mulched all my trees near the foundation of my house, with windbreaks and pine needles under and around and over the pots. My largest elm lost its leaves about 3 weeks ago. Perhaps in the country where I live it gets a bit cooler sooner, but it seems like NJ should be cold sooner than MD. It is my second winter here, and last year the elm withstood the cold winds like a champ. Let the weather tell you when to put them away for the winter. I prefer to leave them outside so I dont need to worry about watering too much.

rockm

I have not stored ANY of my trees yet here in N. Va (Zone 7). It has been much too warm for that. We've only had a couple of frosts and freezes. Some trees still have green leaves on them. Putting those in storage isn't a good thing to do. I plan on moving alot of them into mulched winter quarters this weekend--after the heavier weather --snow/freezes this week. My C. elms are just turning and dropping leaves now. It's been a very late autumn for them.

You are worrying and babying your tree too much. Chinese elm will do fine under mulch and sheltered from wind. One of the most important things you can do is to make sure the soil doesn't stay soggy over the winter and it sounds like the porch will do that. Make sure it stays moist, but not soggy. C. elm can stand frozen soil. Mine have stayed frozen for months, provided they are kept out of the wind.

Nancy

Wow, thanks! I have kept a thermometer outside and, here in Rahway, we have not yet even had a night of 32F. Strange, I know. My Ch.Elm has beautiful green leaves all over it. I'd like to postpone boxing it up, since checking on it and watering will become a messy chore after that. Hmmm, maybe not necessary.... There is so much I don't know and have to learn. I am amazed that the tree can freeze. Simply amazed! I was concerned about the temp. of the water I use to water it. Does anyone else consider this? Not only icy water on a warmer day, but what if the water is too warm during winter (from the house). Wouldn't that be a bad idea, too? I will keep water standing on my porch, I guess and it will get an ice skin on top. Sigh. Sorry for the worrying, but I LOVE my trees that much!

rockm

Nancy,

Tree root freeze all the time. They have long adapted to such things. They are not nearly as fragile as people assume. The majority of tree roots on within three or four feet of the surface. They are well within the freeze zone in winter in most temperate areas. However, with potted trees, the trick is to protect roots from the hardest freezes. That means placing them underneath mulch or some other protecting covering that mimics the earth that covers in ground trees.

I place my chinese elms behind a fence (To protect against wind), placed on bricks on the ground, I then pile eight inches of pine bark mulch (not nuggets, use shredded mulch) over the pots. It's very important that the pots be on some sort of hard surface that allows the drain holes in the pot to function. I then just leave them alone until March. Rain and snow provide enough (perhaps too much in some years) moisture to get them through the winter.

A little science is necessary to understand how trees can freeze. You might go to Evergreengardenworks.com and read the excellent overwintering articles there. Freezing (and you want constant cold temperatures to keep the plants dormant until the worst winter weather has passed) has alot ot odo with intercellular water and intracellular water and which species can tolerate each.

Rule of thumb, you want to protect roots from extremes below 25 F (although some species can handle lower). The mulch covering doesn't so much trap heat, as it prevents the worst of the cold from getting at the roots. It "lags" temperatures, that is, since it has more mass than the soil in the bonsai pot, it takes more time to heat up and cool down. That means it will shield against the coldest cold (unless that cold lasts for weeks) and the warmer days in winter (which can trigger premature budding and growth--which is a disaster).

Nancy

wow, I thank you. Yes, what really worries me is that my porch can heat up on some of those sunny February days. Now I am tempted to place this little tree in the ground, out of direct sun and shield as you've described. It is just a little 8" tall thing, including above-soil root style. I think it'll stay awfully wet outdoors, though. One last Q and them I'm off to the articles you've suggested... on some of those prematurely warm, threatening days (threat to break dormancy), is it helpful to cover the tree to keep it in the dark?

rockm

Nancy, although light plays a primary role in INDUCING dormancy, it has little or no role in completing it. The number of hours or dormancy required varies by species. It can range from several weeks to a couple of months.

Decidous tree rely on increasing soil temperatures in the spring to awaken them from dormancy. They have no way of sensing light, as their "photoreceptors" otherwise know as "leaves ;-)" are gone. They gradually wake up as soil temps rise above freezing towards 40, 50 degrees. That's why maintaining acceptable level of COLD in dormant bonsai is alsmost as important as trying ot keep them from getting too cold. Pots heat up significantly faster than soil, which can force underwintered deciduous bonsai into early growth. That means you can have trees pushing new leaves in mid-February if there's a warm spell that lasts a few days...

Mulch sheds water to some extent. Raising the pot on bricks to prvent drainage holes being clogged mitigates alot of the wetness. I sometimes cover up the surface of the mulched beds with sheet plastic if we're forecast to get gullywashing rain. SNow, by the way, is the best mulch there is. It maintains constant temperatures, melts slowly and is cold....