Answer: Pussy willow (Salix discolor) is available from Burpee. Since it is a fast growing small tree to roughly 20 feet, it is usually shipped in spring as a bare rooted plant rather than sold as seedlings or by seed. You might wish to order the upcoming Burpee catalogs for easy reference; you can do that through the Burpee web site (www.burpee.com) or by calling 800--888-1447. They can also take orders and give you up to the minute availability information on the telephone.
Rather than a book reference, (I don't know of a book devoted to pussy willows in particular) you might find this information from Minnesota Power helpful. http://www.mpelectric.com/treebook/fact101.html
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