Understanding Fall Plantings in Chicago

There is something I meant to rant about a few weeks ago after a quick weekend trip to Chicago. And I forgot all about it until today when, while writing all sorts of tips for an eco-friendly 2009 calendar I'm working on, it popped in my head.

Can someone explain to me why city employees (I'm guessing) descend on downtown Chicago in the fall and rip out all of the plantings along Michigan Avenue and the surrounding streets and dump them into giant trucks to be hauled away? They're perfectly good plantings and most still look just fine, thank you. The plantings are replaced with big beautiful mums and other fall flowers, which I have nothing against. But they just tear out thousands of perennials and, I can only assume, throw them away! That is in no way fiscally (yes, I said it) or environmentally responsible.

Dear Chicago, why not plant a beautiful assortment of native perennials that you keep for more than a season? Perhaps you might plant a few annuals here and there to liven things up and add a splash of color, but you could keep the majority of the plantings year-round and still have pretty nice landscaping. Or, if you must tear everything out every season, at least make sure you're doing something reasonable with all that waste. Those plants better be destined for one heck of a compost pile or I am going to be very disappointed in one of my favorite cities.