Someone suggested stockpiling woodchips for 3 years before their use, which I would consider not just a waste of space but impractical on the issue of discouraging weeds. After 3 years in unprotected storage, woodchips should be well on their way to humus and ideal for seed germination. Wood chips from almost all species of trees are not toxic to other trees, even when fresh, and can be used for mulch right out of the chipper. The old issue used to be tying up nitrogen which research has apparently debunked. Here's a link to back this up. http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/magazine%20pdfs/Woodchips.pdf
[NAFEX] Fresh woodchips are fine,
Alan Haigh, 03/25/2010