no danger that i can think of except as attractor to slugs but that may be totally irrelevant for the plants you have in that swampy area.
best,
mindy

Similar to Mindy's thoughts, the decaying wood could attract many fungi. Which could turn into an awesome mushroom garden.

It's great stuff, I'd definitely use it. A dusting of Sluggo or another of the non-toxic slug & snail killers could be useful, but no more so with rotted wood than with any other mulch.

Of course, this is assuming it's not pressure-treated wood... I wouldn't use that anywhere in my yard, not even on ornamentals.

I have done the same thing with the old logs that decompose for years and get nice and soft. You can crumble them with your hands into a decent looking mulch. I don't see how these would be a problem as a mulch - they're not much different from wood chips.

I'm not using them on the more formal garden though, which is in front. I'm using them in back.

Terrene:

That's what I thought - that they weren't much different than wood chips. My swamp and woods is REALLY informal, but I have a bed of rarer wildflowers and shade plants that I want to keep out ferns and reseeders, so thats where I'm using them.

I was told NOT to use wood chips from trees I cut down since it would attract termites. Not sure if the same applies to your idea tho... Good luck and keep me posted...

If it's really damp, you could probably crumble it up and sterilize in the oven to kill any pests/diseases at about 160F for 20 min a batch. But I second ontheteam about termites. Those things a nightmare, especially if the wood mulch right next to the house.

I haven't ever had termites with wood-chip mulch over more than 20 years, but perhaps I am far enough north that they aren't a problem.

nhbabs - I didn't even know this could happen. Never saw a termite in my life. Until last summer, that is. And they were actually in the packaged sealed bags of commercial red cedar mulch. I just thought they were one of those "beneficial bugs". I mean, they would screen for this, right? Wrong.
Worst of all, they got into several of my raised beds, because the bag of mulch was sitting outside for a month and somehow those things got into bags of compost laying nearby, which I used to fertilize the beds. I had to dig up all the stuff, empty the beds with termite soil and haul it off into the deep woods. There's just seemingly no safe way to get rid of them. Ack.

Thanks all - it is not in a bed next to the house - and couldn't termites get to the house from the woods as well?

Termites do not live or nest in wood. They only work there on a daily basis. They nest underground, and MUST return to the nest every night. If they want to get into something, they will either find a natural path, or construct mud tubes for some length to reach their target. They have to be in a protected and moist environment at all times, hence the mud tubes when they need them. So termites will find wet wood (preferred) when and if they want to.

Termites aside, I just would never use rotted wood as it can harbor a multitude of unwanted pests and diseases. However in your case, if I understood your post correctly,
your just taking what's already in the swamp and breaking it up, so really there's little impact on what nature would do anyway.

Wow - I'm surprised that this thread has gotten so many answers - thank you all. Now you've got me worried about termites. I'm using rotted wood from my swamp area on beds around my lawn but not against the house. I've never mulched before, but have a bed of more dainty , mostly wild flowers, that I don't want to get over powered. I've seen people use wood chip mulch, so figured, how could this be much different?

Re: my last post, any termites that hitch a ride in the mulch won't live beyond a day or two. Once the mulch dries out a bit, they're dead. They need to get back to the nest every night, so unless there is a queen in the mulch that you put on your beds (highly unlikely as they are usually kept safe far below ground) then termites aren't a real threat. But I was thinking that fungi and/or certain insects might be happy to meet up with your bedding plants!