I have a black sage (Salvia mellifera) that has been growing in a half whiskey barrel in my back yard for the past three years.
To plant it, I used regular back yard soil, and I placed a two gallon olla in the barrel off-center to allow more space for the plant’s roots. I planted the black sage, and then covered the soil with rocks from my yard.
An olla is a bulb-shaped unglazed clay pot with a lid. You place as much of the olla under the soil as possible, with just a little bit of the neck and the lid sticking out. Then, you fill it with water, and the water slowly seeps into the soil at root level. Ollas can water the soil around them within about a foot and a half radius.
I buy my ollas from Kevin Polk and Susan Bernardo at Pretty Pots and Beyond, and my half whiskey barrels from Home Depot.
If you don’t have backyard soil available or prefer not to use it, check out the The Theodore Payne Foundation’s recommendations. They suggest using a fast-draining mix containing pearlite, like a cactus mix, or their own potting soil mix, for growing California Native Plants. If you use one of these mixes, you may not need or want an olla. You will need about four cubic feet of potting soil to fill a half-whiskey barrel.