Fishnfarmer, you have waited quite awhile for a response.
I don't mulch much of anything except compost around the potatoes. Beets would be especially risky for mulching in my garden. Well, the risk would be providing cover for slugs.
It would need to be fairly fine mulch for tiny plants. Peat moss or bark dust are the best I can think of. Just my 2Â¢ worth . . .