andyo

I don't think there would be any drawbacks at all to using them as mulch for your tomatoes. They are considered to be somewhat acidic, but so are the shredded oak leaves I use to mulch the entire garden, and everything has been fine for years! Occasionally I sprinkle a small amount of lime on the leaves, maybe every 2-3 years if I think of it, though by that time they're nearly indistinguishable from the soil.

If you've got 'em, use 'em, and count yourself lucky!