I am glad someone is concerned about Russian Sage being invasive. I have seen it spread to wild areas in several states, and I am sure that in a few years there will be Russian Sage eradication programs out west. Every non-native plant brought to this continent is one more roll of the dice to see if we have another purple loosestrife, cheat grass, or kudzu.

Enough preaching to the choir... I think that Pitcher Sage (Salvia azurea) might be a nice substitute for Russian Sage. Pitcher sage is native to your area, and has a similar light blue color. I have not grown it myself, so i don't have any firsthand tips on how to grow it.

Russian sage isn't a shrub, it's a woody perennial. Trust me, you don't want it. They spread everywhere and are impossible to kill off. It laughs at Round-Up.

Vernonia fasciculata (Ironweed) is a wonderful plant as is Verbena hostata. Both bloom a pretty purple color (though not the same exact color) for a good long time. Liatris pycnostachya is another. All are good butterfly nectar plants.

Salvia azurea is s spotty native in IL, based on the USDA site and looking thru various other sites for native plants in IL.

Here is a link that might be useful: USDA

Try one of the large, native salvias - I've seen some growing here in the Wash DC area and from a distance they look just like russian sage...but sorry, I don't know the specific names....BTW, I grow russian sage in my garden and it's not invasive-behaving for me at all - it does well in our dry, humid summers here - Eric

I also thought Russian Sage would be that wonder plant we are always in search of, and it played out that way here in our arid high desert with subzero winter temps. I became alarmed when it became somewhat invasive in a garden setting, but what really caused me to strike it from my preferred plant list was when it began showing up in our native desert landscape. It did seem to respond well to Round-up, especially when mixed with 2-4-D!

Hehe, for me, the problem with Russian sage is its very ubiquity. In other words, I find it woefully overused in the trade, along with such other (to me) boring plants like feather reed grass, knockout roses, et al. Just my personal opinion. My wife wanted us to plant some RS in our home garden. This is where I had to put my professional horticulturist foot down and say 'no more'! Really sick of that thing.

I think the Salvia ideas might get you close.

+oM

Russian Sage is one of the few non native plants I do like because it does so well in our harsh summer heat/drought and it attracts bees and other pollinators like crazy. Unlike so many plants that need weekly supplemental water and even then they struggle or look fried in the heat of summer, it looks good all season. I'm not aware of it invading or displacing native plants anywhere down here. Its used on medians, public gardens and private gardens especially in harsh full sun areas where so many other plants struggle or die. Its often planted in the desert SW for the same reason.

If you want silver leaves with purple flowers, a good native substitute would be Amorpha canescens (Lead Plant) which is a prairie classic. Its roots grow deep (4ft) & it will eventually form colonies but it only blooms once in late summer. It has a wide native distribution.