My poison patch of castor beans is coming up beautifully. There are around 40-50 castor plants in it and their leaves have already darkened to that dusky purple sheen. I've begun using this patch as a graveyard for my ritual remains. One of the most recent things to be buried there was the remains of a Sara Lee pound cake that had been given in offering to St. Expedite after he (with amazing effeciency) helped me out.
Other things that make their way there are wilted flowers that are removed from the ancestral altar, water offered to spirits that has been out for a day or two and needs to be replaced with fresh, and any other biodegradable ritual item that has fulfilled it's purpose and is ready to move on.
Another thing I use my ritual graveyard for is burying items that need to spend some time entombed as a part of their consecration. For some things I will bury them in an actual graveyard, where a close proximity to literal human death is needed for the work. But if the purpose for the entombment is just related to a period of darkness in a sacred space, my ritual graveyard works perfectly. The buildup of energy created from giving back ritual remains to the earth can become quite potent. This can be accessed through the plants that grow there, and also by taking a bit of the soil to add to workings.
The ritual graveyard is also an excellent place for monuments. A statue dedicated to a nature or underworld spirit are appropriate here, because the graveyard is outdoors and the remains are being buried underground which brings in the underworld connections. A tribute to moon goddess works also, and each night it's there soaking up the rays of the moon. Statues or monuments dedicated to meeting of an entity that helped you on your path, or that you had a memorable meeting with also work well in the ritual graveyard. The possibilities are endless. :)
There is a lot of lore about Witch Gardens, disposing of ritual remains, etc. in books and traditions around the world. Nothing I do with this is new and my own invention, I'm sure I probably read of the idea several times before I started working with my version in the way I've described here.