Sounds like a bad situation. I feel for you.

Are you sure there isn't a way to gently tell her her efforts at removal were in vain - that you actually have to dig the stuff out or it's going to return? From what you describe, it seems like she's going to realize the Ivy is coming back in short order.

I'm constantly amazed that there are a whole lot of people out there who don't know how to weed.I see it in my neighborhood all the time. One of my favorite neighbors is constantly complaining to me how many weeds she has in her garden. She does. By midsummer, they're 3 feet tall and overtaking everything. Her solution: She kind of breaks off the tops of the weeds, spreads a thin layer of mulch over the top of them and that's that. It looks nice for about a week until the weeds start poking through again. She just doesn't get it.

I would tell her you sought the advice of some "Ivy Experts" and they told you the only way to eliminate the stuff is to get rid of the root system or it will return. See how she reacts to that and then maybe offer to help her nuke the area with herbicides and maybe the black plastic thing for the season. I have no experience with Ivy, so maybe others will have a better solution. It might be worth a try.

Kevin

it won't be the roots which are the problem but the clinging, climbing, sprawling lengths of vine- complete with holdfasts. They will break through fences, prising apart timber slats,, climb over walls, and once they are mature enough to flower, the seeds will be everywhere too. I suggest a firm dialogue which makes a lot of neighbourliness and communal responsibilities and offers some more effective chemical solutions since only the most sustained campaign of weeding, digging and pulling will eradicate this climbing plague......or you can do what I do in the woods and largely ignore it as just one of those unsolvable things, Depends on the acreage, your vigour or antipathy towards (perpetual) digging and weeding and community relations.

If it were me, I'd spray Round Up extended control on anything that comes over your line. Other than that, you're pretty much out of luck as that stuff will find a way to infiltrate anything you put there. Landscape fabric under stone will keep out new poison ivy and english ivy shoots but it will do nothing to keep what's on her side from growing over to yours.

Keep at it with roundup or a lawn mower, just don't let it regroup!
Campanula already said it regarding the root barrier- don't bother. Ivy spreads above ground, not through underground shoots. The only shoots you may see will be seedlings or sprouts off roots you missed.

Don't do the rocks and plastic, it will be a pain... Just search it. You'll be better off with just wood mulch or grass seed.

Thanks to all for the replies.

kato_b: I don't think grass would work. It's kind of an awkward area, which is probably why someone planted ivy there. There's a rock retaining wall at the back of it, cement stairs and sidewalk boardering it on one side, a cement sidewalk with raised cement border at the front and a cement slab boardering on the neighbor's side. It's also sloped.

I'm reluctant to plant anything there because we've been battling poison ivy in that area all spring and I think it will continue because the neighbor isn't controlling it on her side. I don't have the patience to keep killing it off while dealing with desirable plants in the area.

Is the main problem with landscape rocks dealing with the debris that gathers in there and trying to keep it looking tidy? Does plastic make it worse? Does using larger landscape rocks - like medium sized river rocks - make the problem better or worse? Wood mulch could work but I'm afraid it might tend to wash away because of the slope.

Maybe I'll just let whatever the neighbor has on her side take over (except the evil poison ivy) and move on to the multitude of other projects we have to complete this summer. Gotta pick your battles.

You know, gardenweb should start a forum with tips on how to live in peace with difficult neighbors who share a property line. This neighbor just cut down 3/4 of an old evergreen shrub that was on the line and left the mutilated remains on my side for me to deal with. Is that passive-aggressive or what! It's going to be a long summer.

a picture of the area would help could you plant some tall evergreens to screen her side out? Otherwise invite her over for a glass of wine and try and decide together what would be pleasing to both. she is obviously not the kind of person who wants to be agreeable but if you are new to the area, it is best to TRY first...then the roundup!

I hope she isn't the disagreeable type, I hope you have someone like Kevin's described- kind of jumping on the cleanup bandwagon but just doesn't know how to go about doing it correctly.
Yeah, the nixing of the rocks had to do with all the debris that gets down between them. A leaf blower actually does a decent job cleaning it all out but it takes so long. Also I was thinking that if you weren't sure what to do with the area, rock is a pain to remove and dispose of in the future if you get tired of it.
Plastic might not be the worst idea for that spot. Ivy might not spread by roots, but poison ivy surely does, and the plastic should keep them out, but if it was me, I would give it one last roundup spray, skip the plastic, put down two or three inches of mulch, and be done with it. Spraying once or twice a month should take care of anything that pops through, and if you do decided to plant something there later on it's no problem moving rocks or plastic.