First, there is the matter of statistics. The fewer people gardening in a certain zone, the less data available on any particular plant. I imagine with a lot of plants, to say it’s hardy to zone 2 is as much an educated guess as it is a tested hypothesis.

But you’ve got to start somewhere. That’s where other local gardeners are a tremendous help. If anyone is going to know what will make it in your garden, it’s someone with the same growing conditions. And many people who are still too isolated to find a local garden buddy now have the benefit of internet access, and can consult and befriend others in similar conditions.

In the end, the only one who’s an expert on what grows in your garden is you, and you become the expert by trial and error. That means you will kill plants. You will kill plants. After a while, you won’t kill as many, because you’ll develop a better understanding of your extremely local growing conditions. By patient observation you’ll know, for example, that a certain corner is windy, the snow always melts first by the walkway, and the area by the gutter downspout is always a little bit damper.

On the other hand, I suppose you might kill more, because you may become more willing to take chances. I find my willingness to experiment is constrained by the limits of my pocketbook. I will try a perennial rated a zone or even two zones warmer if I think I can provide the other conditions it needs, perhaps shade and moist, acid soil. But I am more conservative when it comes to an expensive tree that requires a lot of digging to plant–and to dig out again when it dies. Gardeners with a bigger acquisitions budget will be braver.