Lasagna gardening is somewhat unusual but represents a quick way to get started when the surrounding soil is challenging. And in most urban gardens one does need to be concerned with lead and things like that in the soil. What they do is lay down cardboard, then on top of it put grass clippings and dry leaves, then top it off with straw. Let it sit and it will compost in place. This is a method that goes back many years but still has relevance today.
Elle and her group are utilizing a very specific, very unique type of planting. It's called three sisters planting. They take 3 different types of plants that actually compliment each other when growing. This is the ultimate in companion planting. The 3 plants are corn, beans and squash. The corn acts as a support for the climbing bean vines, the beans fix nitrogen in the soil for the high feeding requirements of the corn and squash and the squash provides mulch and root protection for the corn and beans. They are very symbiotic plants that help each other. And, it's a great combination, particularly for a community garden.