The downside to using vegetable matter, or even re-using soil, is that you can transmit plant viruses. Once you get a virus spreading you may as well give it up!

I had a sick plant...Yellow leaves and stunted growth. I tried hard and kept everything perfect. All other plants thrived but this one was crap. I pulled the plant and dumped the peat/perlite mix into the soil bin. I mixed it all up and the next crop ALL the plants were yellow and stunted and sickly. I think the virus was in the root cells and spread throughout the soil mix. I still use my soil twice, but if the plant is sickly and I cant bring it back I pull it and throw the soil out in the yard!

For mulch I use 1/2" deep layer of 1/4" screend gravel in buckets outdoors. It really protects the roots from the heat and keeps holes from washing in the soil. The roots grow right up to the base of the gravel and utilize all of the medium.

I use nothing indoors (indoors you generally want them to dry out quickly and would not want a mulch).

The "tea" made from water hash is bound to be good. I use it when I have it.

I generally put the stems and leaves in the wood stove and smoke em.