May one use dry Sechach, such as palm branches that have become dried up?<a href="#_ftn1" name="_ftnref1">[1]</a>
Yes. There is no invalidation of Sechach that is dry and it may be used even initially as Sechach.
<a href="#_ftnref1" name="_ftn1">[1]</a> See Yalkut Avreich p. 29

Shulchan Aruch HaRav | Is dry Sechach Kosher?

May one use dry Sechach, such as palm branches that have become dried up?[1] Yes. There is no invalidation of Sechach that is dry and it may be used even initially as Sechach. [1] See Yalkut Avreich p. 29