My dawn redwoods (8 in total) were planted around April and are now 18-24" tall. Have in a mostly inorganic mix of Diatomaceous earth, Pumice, lava rock and pine bark. I'm going to leave outside but was wondering if the mix they're in is prone to root freeze or not the best mix for winter. I could hypothetically put in a box and cover the containers with soil then take other steps to protect them but was wondering what other people's experiences are. Also a pruning/growth question. Goal is to get the trunks nice and fat, should I let grow and not touch or would pruning this late so anything. I'm in Jersey City, NJ so winters do get cold but rarely does it stay below 20. This was them 6 weeks ago.