I would put Mulch down as newspaper will dissapear to fast.... using much is good to keep the dirt moist and weeds down and also when it decomposes its good for the trees..... We don't use collars with vent in them and don't have any problems at all and we have a nursery with hundreds of trees in the tree fields..... Well i shouldn't say none of them have vents some of our stuff has holes and some don't...