Other trees (Chinese elms, for one) are doing similar things this year, so just not dropping leaves may not be a problem, but I do wonder if it did get too cold as you haven't said how large the container is. If it's just in a regular bonsai pot proportional to it's size, the roots may have gotten too cold overnight. You can make a firm scratch on the trunk to see if it's still green under the bark, and if so, then get the pot into a larger one of mulch, with 1-2" on top as well, and do keep it on the porch against the house. Even though a particular species might be rated at a certain zone, one has to consider the size of container it's in and think of your climate as being 1-2 zones colder than it actually is in terms of root protection.

QQ, I was pulling your leg - I wasn't offended so no need to apologize :-) You do make some valid points. I certainly can't speak to the knowledge base of nursery sales staff across the country and no doubt there are nurseries everywhere that have their share of less-than-well-informed employees. The nursery that is referred to in the original post of this thread is a case in point. One thing to consider is that to the customer, anyone working at a nursery is considered by them to be a "plant person" - this includes even the temporary seasonal staff, often high school kids hired to water, stock or run errands and load cars. And I can't tell you how many times I've encountered frustrated customers trying to ask plant questions of our Guatemalan production crew, who barely speak English. As to why don't more nursery employees participate on these forums, I can't answer that question. Maybe they don't care to admit to it, as iVillage does have restrictions regarding business interests and they think that revealing their occupation somehow violates this restriction. Or perhaps it is a time factor. Personally, I am a self-admitted plant geek and reading about, growing and discussing plants absorbs me more than it probably should. I am a bit obsessive about learning about plants and the forums are a constant learning experience for me as well as place to share the modest amount I do know. And the "We don't carry those. They don't grow here." statement is more relevant than you might think. Customers ask for the strangest things and at the oddest times of year (I had someone in looking for basil last week - last frost is not until early May). I might modify that to read "We don't carry those, they tend not to do well in our area", or won't survive the winter, or they're considered invasive or too disease-prone, etc., etc.

A few more observations about this Ginkgo. Gauging this tree to be 25 + years old. Not a sign of it ever being grafted not to say it isn't. It never dropped any fruit until last year that being only one piece. This year I saw three pieces of fruit on the ground. I always thought it was male....now bisexual??? Maybe it needs a sex change operation. Until 3 years ago it never turned color. Always stayed green until the first hard freeze hit it....then it would drop all of its leaves in one day. Moving on... I have many other dwarf Ginkgo's that always color up in the Fall with the exception of one...'Jade Butterfly'. Dropping green leaves now. So go figure...many factors inter in to color change and I think your micro climate is one. Of course there are other possibilities that come into play which I am not going there. Merely a guessing game. Here's another one growing in the city. A completely different growing form and bark a dark color. Dave

It's growing too fast...probably stretch marks of some sort