Experts and BHG readers answer.
sedums too tall & split in center
Some sedums simply have a tendency to flop as the flower heads form. It could be an indication that they're growing in too much shade or are getting too much nitrogen, but this condition can arise even in full sun or with low fertility. To prevent it from happening, you can pinch the stems when they are about a foot tall to cause them to branch and be less top heavy.