Burrowing substrate

I plan on cleaning my Kingsnakes tank out in a little, but I don't know what type of substrate to put in her tank. I currently have dry eco earth and she can't burrow in that, so I was thinking aspen but that doesn't keep humidity at all. Any suggestions?

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i would use aspen, it is great for burrowing and for humidity i recently saw someone on here use some moss in a dish and they said it works so maybe that? i use aspen for my BP and it seems to do the trick and have not had humidity issues, but in case i ever do i also made a humidifier for the cage and i also have a repti fogger that works well.