Well, in the federal government's definition of an invasive species, a species cannot be invasive within its native range. According to the USDA plants site, Illinois is fully within its native range: http://plants.usda.gov/java/profile?symbol=CLVI5 .
Of course, many native species can be aggressive spreaders and thus unsuited to formal garden situations. Like a lot of other vines, the Clematis species have a bit of that tendency, although I've always heard that C. virginiana is better behaved than others.

BTW, I'd be willing to take some of your seedlings if you want to get rid of them. :) (I just planted one bareroot a few days ago and the darn squirrels dug it up.)

Thanks! That's always what I thought, but you never know, I could very well think wrong ⺠Uhh...formal? Not me, not even a little! Now with my friend, she doesn't mind plants touching each other, but if it sprouted at her place like it's doing here, I'd never hear the end of it!

Is it too warm to try and mail them out? I've never done it before, so I really have no clue. You can e-mail me thru here though and we can sure discuss it. As for squirrels, I hear you and I feel your pain! I've got squirrels all over. Most of my trees and shrubs, and yes some perennials, are in chicken wire cages. Because, as you've found, they like to dig up my freshly planted plants or just small ones that have only been in for a year or so. You name it, they'll dig it up or they jump and break, they bend them down and chew the leaves. I discovered today that they've almost destroyed a Aesculus parviflora (bottle brush buckeye) on the side of the house. Thinking it would be safe on that side, it didn't get put in a cage. I don't get what they're doing or why for that matter.

I guess they think the roots just might be some tasty nugget they buried & forgot. They've destroyed several of my plants, but so far, I've noticed that if a plant survives the initial frenzy of digging, they rarely go back & dig more. I've put up chicken wire around some of the plants, but the unprotected ones always have to face that initial attack.

I'll contact you about the seedlings. It may be a bit too late, but if they would just be pulled anyway, it might be worth a try. We've had rainy & 40s here for about the last 3 weeks straight, but that's supposed to change.

Terryr, since you were in drought conditions there may not be much of squirrels normal food available for them. Does your drought continue. If it does please put out water for the wild ones. I use the small size black concrete mixing tubs. Mine are not sunk in the ground but would look better that way. You do need to keep what ever you use clean or at least well rinsed.

maifleur, last winter brought us a lot of snow and this spring, we've seen our fair share of rain. The squirrels are fed peanuts by us, neighbors have oaks and walnuts and I've sure pulled up my a lot of those the squirrels "planted" that have sprouted. I have 4 birdbaths, all with fresh water put in them on a daily basis.

amelanchier, we've been running in the 50's-60's for temps. The entire foundation was planted with peonies when we moved in. By a previous owner, not by me. I've dug all out (that was a treat! They were huge!), but I did leave one peony, just for my own sentimental reasons. Usually this time of year they're done. This year, the peony has finally gotten buds, but haven't bloomed yet. Somebody told me that squirrels smell our scent on the new plants and that's why they dig. Now if that's true, I don't know, it's just what I was told.