Overwintering on a balcony

Hi all. I am new to the art of bonsai this growing season and have collected numerous specimens. I live on the 17th floor of an apartment building and dont really have the option of putting my trees in the ground, except for driving them an hour to my sisters farm. I'm in zone 5 and really need some advice on the best ways I can overwinter on my balcony. I'm not too worried about my hardier trees such as Scots pine and eastern larch but am worried about my Zelkova and my Japanese Maples in particular. I'm thinking that my smaller trees could safely be kept in a fridge for this season.
Any advice anyway? Anything will help.

Thank you, Mike

I think your Zelkova (if it really is one, they are often mislabelled Ulmus parvifolia - Chinese Elm to get around import restrictions) and Japanese Maple should be fine. Just insulate the rootball with a few layers of bubble wrap or similar. Note that I'm in zone 9 though, so advice would be better from someone within your zone.

I have a buddy who has been growing bonsai on his balcony for years. During the winter, he moves the hardy trees into a spare bedroom with the windows cracked a tiny bit to keep the temperature around 40 (4 C). If you don't have that option, use the refrigerator for small trees. I've done that & it worked fine. Store them in baggies or they will dry out. Another option is to put your trees in thick picnic coolers against the house wall. Bubble wrap would not be adequate. Even your hardiest trees should be protected around the roots.
There is a very active Toronto Bonsai Society. Be sure to contact them. torontobonsai.org/
Iris
Also Zone 5

I am also in Toronto, also going to overwinter on my balcony for the first time and also 17th floor.
And also I am a recent member of the Toronto Bonsai Society LOL

There is almost no one who overwinters on their balcony in the club because most members have gardens. One lady does overwinter in the balcony but does not keep the bonsai on the balcony during spring, summer and fall.

I share the same worries about my current trees and this year's winter. I have spent a lot of time, resources and effort to have them and I really like them and look forward to keeping them as long as possible. Possibly, always on a balcony too.

I am originally from a tropical country and have no full understanding of plants here and how they function throughout the seasons. I have heard and once seen in Toronto, a tent in a garden where the bonsai roots, out of their pots, wrapped in burlap, buried in the ground. Also heard of Styrofoam coolers punched with drain holes where bonsai is placed and pot/roots buried in peat moss, dead leaves and mulch and occasionally snow added in. I have heard of the greenhouse method and fridge method.

That said, the greenhouse and fridge method is more quantitative.
Can different outdoor species from different zones (including delicate Jap Maples and such) be overwintered together in a controlled environment - temperature, humidity level, light levels-natural or artificial, fresh air supply and occasional addition of snow.

I have been thinking of designing and building a fold-away green house with a glass top (made by ordinary window suppliers) to be put on my balcony, 17th floor, east facing. It will also have an automatic heater in case it gets very very cold.

I have kept astilbes, hostas and lilac on my balcony in commercial outdoor planters successfully and sometimes not. I did not provide insulation nor Styrofoam lining within the planters. So I was always anxious when spring comes because it was unpredictable if they were still alive or not. The ones that did survive are very late in the season. Irises have bloomed weeks ago, mine is only about to reach their full size before blooming.

For Bonsai, what is the key thing to wake them up in spring? X number of morning/afternoon sun?
Natural rainwater? Fresh air? Fertilizer? Raking?

Also what happens and what do you do to bonsai when autumn comes?
I would really appreciate any advice.

Thanks !

Get trees that can live where you live.
Don't get trees that need special treatment for winter.
Especially if you have no place to put them for winter.

I would take the deciduous trees and place them in the barn at your sister's place or a sheltered spot outdoors (like next to the barn). Bury the pots in mulch and they will be fine. Water well and let the pots drain before applying the mulch (or straw). They will only need water every month or so if that. The concrete deck of your balcony is not insulated, like the earth, and there will be cold winds up there. Just my opinion.

People have reported very mixed results with refrigerators. However, Iris' suggestion of creating a 40 degree room will work very well.

Best of luck!

You do have a problem with winter care for your deciduous bonsai but you have a contact with a Bonsai Society in your area.. Our members are very fortunate to have several growers who rent space in their cold frames for the winter.
If you really want bonsai that reside with you I would think about indoor growing. I have been growing tropicals for years in the house with the aid of florescent lights and high intensity plant lights.

It's really too bad you had to have this boxwood problem. We all have lost trees especially when we first began growing bonsai!! The tree may not live especially since they are evergreen leaves. The boxwood is a favorite of mine...I hope yours will survive.

Good luck, Norma