eChinese Cork Bark Elm - To Dormancy or not to Dormancy...that is the Question? (Sorry, William S.)

Two years ago I purchased (as surplus), a Chinese Cork Bark Elm from the Bonsai Collection of our Chicago Bontanic Garden. Over the Winter of 2011 - 12, I allowed it to go dormant. And the tree was fine this past Spring (2012). Then my sensai (sp?) at the Garden advised that this particular tree could also be grown as a tropical. So alas, I saw great and obvious advantages to giving this tree a longer growing season. So I brought my beautiful Elm in with my other tropicals this Winter (2012 - present) and put it under lights. It has not done well to date. My tree is not growing at all and it has continued to lose its leaves (i.e., the leaves turn yellow and drop).

So what to do? Should I give it more time in its current tropical setting or should I try to induce dormancy at this time? Frankly, both options have negatives. The tropical atmoshere in which the tree currently resides might ultimately kill it. Or the shift to colder temperatures (to induce dormancy), this late in the season might damage or kill it. So what to do? To be or not to be...! Thoughts please. Thanks.

Hey Bob,
Also being in the Chicago area I Have similar experiences. I have found that allowing the trees to have a dormant period is better than a longer growing season. As with my tropicals I feel that through the winter it is a matter of keeping them alive and reasonably healthy until they can go back outside. With my seiju elms I have for the last two seasons let them go dormant and kept them in my unheated garage until about February then brought them inside for about 6-8 weeks until the weather warms up enough for them to be outside. This extends their growing season a bit but also gives them a dormancy period. Last year I kept two airlayered trees indoors all winter in order to promote root growth, but the branch growth was weak and lanky, so it was cut off in late spring.

In regards to your tree I would keep it indoors until the weather warms up. Trying to induce dormancy now would be tricky and risky. The tree needs a slow gradual decline in average temps over the course of a couple months in order for it to prepare for the winter cold. Providing more light and humidity might help it now, just watch the watering so it does not stay too wet.

Todd

since i dont have a greenhouse...i do the same thing with my tropicals...bring them in for the winter and just kinda keep 'em alive...they never flourish indoors for me, but thats ok since i mostly bring them in for root growth anyway...i think, you're sensei is correct in that it can be grown as a tropical (ive also heard that they do this with azalea as well during the first part of development)...the problem for your average grower however, is that the inside of our home is not even close to the conditions of a proper greenhouse...so, maybe under greenhouse conditions this species could be grown year round with good results, but in a home enviornment, maybe not so much...

Thanks for the thoughtful response to my Elm problem. Guess I will leave it indoors 'til Spring this year. But next year is gets a proper dormancy period!

I have numerous Chinese Elms, most are Winter hardy in this 7a zone climate. Some are not; these were older imported Chinese Elms. For these older trees, I let them stay outside until they drop their leaves and let them sit on the benches until temperatures drop below 25 f consistently, usually by Xmas time. I then bring them indoors and grow them under fluorescent lights for the remainder of Winter and early Spring - then they go back outside, usually in April sometime.

For those elms which are Winter hardy I place them on the ground in a protected spot and mulch their pots; they do fine with this treatment. I suspect that Illinois is much colder than Central VA Piedmont so better protection is certainly indicated.

I have been told that some of the imported elms will do well when treated like other tropicals; I just know that mine do better with some exposure to frosts and freezes. To answer your question - I would leave your tree indoors until temps are above freezing; probably late May in your climate... Good luck!
Todd