It has been extremely hot and dry here and a challenge to keep things even minimally watered. Some of my sibs are looking more dried out than usual, will this kill them off?
Siberians in a dry year
depends on the cultivar. Water even with a watering can if you are able.
Probably won't kill them, especially if big clumps, but late August and early September is when they set buds for the following year, so if they are stressed then, next year you won't get as much bloom.
Most of them look like they have survived, but I have a couple clumps that are mostly brown and dried up. Should I just cut them back and hope for the best?
they have huge root systems so I would douse them with water if you can so they will set buds for next year.