Well I prefer the well lights on walls, trees, etc. I do not use anything to cover the light. I wonder even with a cover will the mulch still catch on fire? Seems to me that heat would still build up.
On that note. I do tell my customers DO NOT cover the fixture with mulch or line needles, or it will catch on fire. I have had 2 service calls to where the mulch has caught on fire, due to who installed the mulch.