Hi, first of congratulations for reviving your Coffee tree. It is pretty unusual for it to come back to life after spending two winters inside and no water for a couple of months. I'd say you tree is a tough survivor. The coffee tree (Gymnocladus dioica)is a tree that needs to be outside. It is ok to bring an outdoor bonsai inside for a day or two, but not longer, and not during the winter time. The trees in the temperate part of the countries are adapted to the winter resting period. By keeping it in the apartment for two winters you stressed this plant to its limits. I suspect that the green sprouts you are seeing right now are emergency shoots, basically a last ditch effort to get some photosynthesis going and to store some energy to make it past the next winter. I have a Japanese maple variety that also decided to sprout some fresh new leaves in late September. Not much you can do there but keep it watered and hope the tree will realize the error and move into fall mode soon.
In terms of what to do at this point, that's tricky. Don't bring it back inside. Even a cool room in the house is mostly still too warm and you would definitely kill the seedling this time. I would leave the tree where it is for now, and hope that the dropping temperatures will signal it to stop growing and to prepare for winter. Keep it moist, but not waterlogged. Do you have the option of wintering it in a friends yard maybe? That would be the best option, to sink the tree with the pot into the ground, fill the ground soil back around the pot and cover the whole spot with potted tree with a good layer of mulch. If possible, choose a spot that doesn't get any sunlight and good protection form cold drying winds. Snow and rain are good, your tree needs those elements.
If you don't have the option of sinking it into the ground you can also try to get a box or larger flower pot, fill it half styrofoam chips, sink your tree and pot into it and cover it with more styrofoam chips. Move it into a corner out of the sunlight and protect it from the cold drying winds. Check occasionally during the winter to make sure the soil is still moist. Water it if needed, but don't overdo it. Next spring, if it survived the winter, you need to carefully nurture it back to strength and health. Do some reading during winter on the care of over-wintering options for people with no yards and outdoor trees. Good luck with the plant, I hope it'll make it. Maybe others will give you their opinion and advice as well. Please let us know how it fared.
Marc

Hi Marc,
Thanks so much for all your advice!!! I don't have any nearby friends with yards (most of my friends are also grad students who live in apartments), but I'm going to try your large pot with styrofoam chips idea.

Your suggestion on reading is very appropriate... I sort of just thought I could turn them into indoor trees! I'm coming 'round to the idea that you can't force trees to do what you want! This explains the complete failure of all my other 'outdoor northern temperate zone tree' bonsai attempts (blueberry bushes, apples, maples, oak...). I will finally admit that it just doesn't work and do some reading :)

Thanks again!!
a

Hi everyone,
I was blessed to have produced some trident maple and Amur maple, and Chinese Lacebark Maple and a couple of other seedlings this summer. Now I am in a panic as to how to overwinter them for my future bonsai projects. I have them in the " chicken coop" i.e. outdoor shed with windows. Then I was going to move them to our 150 farmhouse basement with lighting. Do they need to lose their leaves and go dormant, or should I try to grow them all winter this year and work on the dormacy next year when they are bigger? Thanks Sheri

I keep thinking about your post and your little tree. And I must confess, I am curious... Kentucky Coffee tree is not a very widespread tree species, nor is it known very much. I don't believe I have ever heard off or seen any Coffee tree bonsai. What made you start seeds from that native tree? Any particular reason?

Kentucky coffee is not uncommon from zones 6 and up, even if it's not well known where you are - I did have one (bonsai) years ago that I got from the U.S. (when you still could get away with it!).

Hey Lucy, that is great to hear. Can you tell me a little more about your experiences with this tree as a bonsai? Oh man, I feel that tingle in my stomach, I got to get a coffee tree started myself now...lol

It seems to me that if this tree has had no foliage for some time, it must not have much in the way of energy stored in the roots. The fact that it is budding now leads me to believe it might be prudent to take it back inside and give it artificial light to allow it to grow foliage. I know that is risky, but I just think that at this point, it might not survive the winter anyway - without energy reserves in those roots.

Matt

Marcindy - I'm trying to figure out why it's planted in sand and vermiculite - not at all a good mix and probably responsible for why it's done so badly. It needs soil with coarse particles (not the small fines of peat that are in most potting soils) mixed with a lot of grit (perlite, aquarium gravel, chicken grit, etc.). Vermiculite is going to 'clog' the soil, not allowing oxygen into the soil, or proper drainage. You can overwinter on a balcony, but need a large container with good sized drain holes, into which you sink the pot up to the rim, then add mulch on top (couple of inches) but not right against the trunk. Water only when the soil is NOT frozen but not as often as you would in spring or summer, but enough to run through. If snow falls on it over the winter, that's fine. Don't remove the mulch til after the last frost in spring (could be late April).

The large container can be filled with soil or mulch (sorry I missed that out!).