what trouble exactly do you anticipate?

It could be composted, if you are looking for a place to dispose of it.

Usually I would just mow it, hose it, or sweep it into the lawn. I never took the effort to "pick up the piles".

Make sure you sweep of the AC unit. Cottonwood likes to stick to the vents there, blocking air flow.

The cotton contains seeds, does it not?

I'm assuming that's what jcgardengirlmn is worried about.

Go ahead.. throw it in there. Won't do any harm. If your compost is working well enough, any seeds will be destroyed. If it isn't, the seeds will grow into trees which you can then pull out or clip right back into the compost.. simple!

Check the label on the tree, some cottonwoods are blends, and may contain rayon and nylon as well.

Dave, who has a forest of the things directly upwind, and is getting ready for the fluffy onslaught. Which shouldn't be confused with the thistle fluff onslaught, the milk weed fluff onslaught, or the cat tail fluff onslaught.

I can't just leave it. We tried to mow it back in the lawn and my lawn is a solid mass of white not to mention the sidewalks and driveway. It's like Christmas here. Yes, I am worried about the seeds and I did tell my DH that it may go in the pile this year and then we'll see how good my composter kills the seeds. I have a brand new pile (had a townhome last year) so I'm nervous about putting it in my new little pile. Then, of course, the question comes to mind as to whether it is a green or brown? I'm thinking its dry enough to be a brown.

If the pile is too small, it may not get hot enough to kill the seeds. But any weeds (and the cottonwoods would be weeds in this case) that sprout in compost are very easily pulled.

It's probably a brown, but probably a pretty insignificant brown. I know it seems like a lot, but it's so fluffy that it weighs next to nothing and the green/brown calculations are by weight, not volume.

Think of what that "cotton" contains. If there are seeds in there they will have everything a new sprout will need to live on for several weeks after they germinate. That would be a very good addition to the compost pile and should be a "green" rather than a "brown". Proper handling of the compost pile should be enough to kill anything that germinates from those seeds, turning as often as necessary, covering the material with more, different material, getting the pile cooking.

The seeds in the cottonwood fluff are very small and it is mostly fluff so I'm still tending towards thinking brown. It may not weigh very much by volume, but when it is enough to fill up the composter (yes, I dared today) to the top when there was previously barely enough compost to cover the bottom, there's probably some weight all together. It will be tough to find out since when my DH raked it up, it also raked up grass clippings so who's to say how that will affect it. I guess we'll find out how it goes since I just dumped the whole thing in. I figure it will compact fairly quickly so I'll still have room to add more compost.

That sounds like a great compostable. I've never seen something like that, sounds kinda neat. It's like you've a green and brown in one ingredient. Pack it in and water it down. Add a little fish emulsion and let 'er go. Ol' Mom Nature has given you a gift.

Gift? Well, we'll see how it composts. Some communities around here won't even let you plant cottonwoods anymore because they're considered a nusiance plant (ie. cottonwoods, cottonwoods everywhere). That's why I'm hoping the pile heats up nicely. It was warm the other day but not yet hot.

I live with these trees. I can honestly say I love them for their shade, but I loathe and dread the "cotton season". I found that it tends to "shield" up once water hits it, forming an outer wet blanket. Once you try to move that wet pile of cotton, you release the dry, fluffy flyaway stuff underneath. So it's hard to manage into the compost to start. Maybe the grass clippings mixed in IS a blessing? Something needs to be ground with it to weigh it down enough to break it apart. I've put it in my compost pile only to regret it for these same waterproofing properties.

Funny story, my DH's parents bought "poplar" trees thru a catalog company a long time ago. The trees came and my DH and his Dad planted them. It wasn't until they started blooming this cotton several years later that they questioned whether they were poplar or not. Luck would have it not. DH and I are strategically removing them one at a time. We are replacing with other trees.

Did something very similar Robin. Planted several fast growing hybrid poplars when we bought our house, with maples and oaks in between. They were great for fast shade in our barren yard. When the other trees began to reach a good size we took out the poplars one by one.

Back to cottonwoods: We had a hybrid one whose cotton stayed mostly attached to the twigs so it would come down in a clump and was easily picked up. We did not get inundated with cotton like the OP, thankfully.