I planted a new cedar hedge 6 weeks ago and some of them are changing shade and now dying. I.dont know.whats happening because it’s not just individual branches going brown and dying but the complete tree goes limp all at once. The trees are on a soaker hose so I dont think it’s lack of water and the unaffected trees are doing well. I’m wondering if it’s root rot or something like that and may be spreading. The trees are from Costco.
It’s probably lack of water but you don’t say what type of ground you have. However, first of all it is not an ideal time to plant cedars at the end of spring. Secondly, the root ball will have been cut back quite a bit so the tree is stressed anyway. And finally, probably not the best quality tree anyway. So you can either return them and try some other ones or try to resuscitate them, they need a good soak twice a day, if hot then three times a day until fully established.
Many plants that have been in pots are quite root bound, and even if the soil around them is damp, the roots themselves are not. I have found that for new plants that have been in pots, soaking the whole root ball in water before planting, then watering directly at the root ball for quite some time until established helps get them started. You want to encourage the roots to move out from their potted ball, but if the root ball is dry for an extended period of time, the plants are pretty sad and they can die before that happens!
Is it possible they are over watered? I noticed water pooling sometimes, although the water drains away after a few hours.
Could it be root rot?
Is it possible to revive them once they turn pale and limp?
For what it’s worth I’ve heard a number of people say the same thing about the cedar trees they got from Costco. I think what @royheaton has said is sadly correct. It would be much better to buy smaller trees from a nursery and plant them in the fall or early spring. Smaller trees with good root systems will establish much better than bigger trees. This is assuming that the ones you got are more than about 2 feet tall.
Perhaps you could post a picture of them? I doubt that it is root rot; more likely to be compacted roots and the water just never gets into them. One thing you could do is dig one up and see.