I think subject says everything - now it does not. Could you please add this?
Didn't test it for silverwood leaves, but would be also nice.

Thank you.

That's not on my end, it won't break blocks that are a subclass of BlockLeavesBase. https://github.com/Vazkii/Botania/blob/master/src/main/java/vazkii/botania/common/item/ItemGrassHorn.java#L116