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Gardeners in the suburbs and Indiana had been reporting the same thing on the Gardenweb forums and I just saw a post on the CL garden forum from a person in Long Island who has Hyacinth bulbs breaking.
It got me curious so I called the U of I Extension number and spoke to Nancy Pollard. She seemed a little surprise to hear that I had bulbs sprouting in Chicago already.
I asked what course of action she would recommend and she said that mulching would be an option to help protect them when winter finally arrives for good. But with mulching there is the possibility that you could do damage . You see the growth we have now is being fueled by the bulb's reserves that it collected during the last growing season. If you mulch or cover the bulbs to protect any green growth now, you're prohibiting the bulb for collecting energy for the next growing season.
If these bulbs continue to grow and start to flower and then winter finally arrives they will suffer damage that we'll notice in the '08 growing season. If your bulbs are sprouting now it's better to just let them be because they're strong enough to survive cold temperatures when they finally get there. Chances are that they'll flower in Spring but if there are any negative effects it will most likely be little to no blooms in a year.
Nancy Pollard recommends to just let nature take it course and hope for better luck next year.