Answer: Lilies will go dormant at different rates depending on their type and on their planting location. In general you will find that lilies of one variety will die back at approximately the same time, but not always. In a dry year they will dry out and turn brown sooner than they would in a wet year. Deadheading seems to prolong the green stage, also. In my experience the time to worry is when they start to shrivel or appear moldy or mottled or turn black during the summer. Once the stem can easily be removed cleanly by hand go ahead and do that, being sure to remove it from the garden to reduce chances of carrying over any possible problems from year to year. As long as the changes seem to progress cleanly from green to brown and it is fall then they are probably okay even if it is before frost.
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