I have the ultimate container garden. It is an 18' boat. We put tree limbs and rocks in the bottom after we drilled holes in it. Then we began to mix manure, top soil, sand, peat moss, and garden soil to fill it. I have been using it for 5 years now and it grows very nice leeks, garlic, green onions, shallots, and lettuce in winter. My garden has a clay underlayment, so it doesn't dry very well in the spring. It has to be tilled in January before the spring rains begin, or wait till May. The boat gives me the opportunity to start seeds, get seedlings from the greenhouse going better, and grows great alliums.
I will need to add some soil to the top soon as it has settled and I like to have it up where I can get to things easily. I'm old and it makes for easier planting/weeding/harvesting on an old back. I use an adjustable cultivator tool to aerate and weed. I usually let the onions go to seed there so I can get new seeds every year.
Mushroom