I use them a lot, mainly for mulching, then they gradually get incorporated into the soil. Apparently they are a good soil conditioner although they don't have much in the way of nutrients. If you search this site, you'll find quite a few threads, especially from our sadly missed Supersprout, who swore by them and even planted toms on top of bags of hops. One warning- I discovered recently that they can be toxic to dogs if eaten, especially greyhounds.