Ideal mulch bed thickness.
This is a quickie but still very important article on mulch bed thickness. A member of the Gopher Lawn Care Business Forum asked “I am doing a mulching job for an apartment complex. I was trying to decide how thick I should lay it. The landscape has no existing mulch. Should I lay it at 3 in. Or less, like 2.”
Here are a couple of responses that will help you out. One lawn care business owner said ” A few factors such as type of mulch, type of bed, and reason for mulching determine how thick you should mulch.

mulch bed
As a general rule of thumb:
3″ of mulch in shrub and flower beds
2″ of mulch around trees”
Another said “on a new bed (no existing mulch) I usually lay it a little heavier 3-4″ and on existing beds 2″ to freshen up and 2″ around trees.”
Just to round all that great information off, here is one last view point “I always lay on about 3-5 inches of fresh mulch for new beds. If I am putting mulch in a bed with old mulch I always turn the mulch first then add 2 inches to freshen it up. But again it depends on the mulch too. Coco bean mulch would require much less to cover where as a heavy shredded Cedar bark mulch require more.”
I hope this information helps you with your landscape projects.