|The green stem of the legume palo verde tree in the Sonoran Desert.|
Using legumes in the garden can be quite a useful way to fertilize your plants naturally. Farmers in the Midwest will often alternate between corn and soybeans, taking advantage of the fact that soybeans naturally replenish the soil with nitrogen fertilizer that the corn can use. In deserts, which have soils that are naturally deficient in nitrogen, plants must either be adapted to living in soils with low nutrients or have the ability to fix their own nitrogen. For this reason, legumes are extremely common in desert ecosystems. Legumes are not just your typical bean plant, they also grow into bushes and trees. In the Sonoran Desert palo verdes, mesquites, ironwoods, and acacias are all small legume trees that form bean-like pods. Typically, these legume trees will form islands of soil under their canopy that are rich in nutrients compared to soils beyond the canopy. Because of the slightly richer soil many smaller plants will often be growing in this micro-environment.
|The darker growths on these plant roots are tumors infected with rhizobium bacteria.|