Fuzzy matching a tree structure

I'm looking for a good way to do fuzzy matching of a tree against a family of trees.

I know how to look for an exact match between two trees. Just do simultaneous traversals down both of them and see if they're the same.

Now, I would like to (1) quickly match against multiple trees, perhaps on the order of thousands of trees; and (2) do a fuzzy match (for example, severals leaf nodes may be mismatched, but that's ok).

For an exact match against multiple trees, I could hash each tree. But the fuzzy match against multiple trees seems difficult. Any ideas?

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