Colchicum Help needed

Does anyone here have experience with Colchicum? Giant. I bought some last fall after they bloomed and potted them up. This spring the leaves grew and they seemed happy. Then, suddenly in the last couple of weeks all of the greenery turned yellow. Is this normal? I've checked a few sources that indicate that the leaves eventually die in the summer, but this seems quite sudden for a bulb that won't bloom until fall. Zone 7. They are in a large pot and outdoors for summer. Thanks.

Yes, this is the time of year that mine suddenly turn yellow and limp. I tug gently on the foliage; it will pull out easily when it is ready to be removed. Colchicums are dormant during the summer and will put up their flowers with no foliage in fall. In late winter/early spring the foliage will emerge again.

'The Giant' is hardy to zone 5 so you can plant them in the ground if you want. If they are happy they will multiply rapidly for you.

I also noticed that the foliage pulled out easily, and was very worried that I'd killed them. Thanks for your help!