Answer: There are many different types of lettuce and most do not form the round heads like we see on Iceberg in the grocery store. To grow its best, lettuce needs cool temperatures (under 70 degrees) and evenly moist yet well drained, rich soil. This allows it to grow quickly and stay compact. In hot weather it deteriorates quickly.
For home gardens, a good strategy is to grow leaf lettuce and harvest it several times in a cut and come again technique. This lets you enjoy home grown lettuce over a longer period of time, before the summer weather hits.
Based on your description, I think your lettuce may have started to bolt or go to seed. When this happens it is no longer tasty.
Here is more information on how to grow lettuce you may find helpful, including recommended varieties for Illinois. You can try again for a fall crop.
You may need to cut and paste the complete url into your browser to make it work correctly. Good luck with your lettuce!
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