Okay - I see this conversation has happened down below on another thread, but still asking "when" I should put it down. It doesn't sound like I need to worry about shredding it, though I may run over it with a lawn mower first, then use leaves this fall to start my mulch for next spring.

It seems to me that if the leaves aren't shredded, they would prevent water from being able to penetrate underneath.

You put it down when the seeds have turned into seedlings. Put down 2 -3 sheets of newspaper first and use the leaves to hold it down. Also make sure you protect the tender stem from water by creating a crater around it to collect the water. Shred or no shred it doesnt matter but unshredded may start to stink after a good rain. It will all get shredded eventually when you till the garden for next year anyway!

organicislandfarmer, thanks for the info. I plan to put down newspaper for plants and cardboard between rows. And use pine needles and partially composted leaves as mulch but wasn't sure how to put it all together. I used straw only last year but didn't use enough. Hope to get some more this yr. Didn't know about the "crater". You have been most helpful.