The following article was written for and published in the summer 2012 Fallbrook Land Conservancy’s newsletter, the Conservation Chronicle (http://www.fallbrooklandconservancy.org/News/Chronicles/Summer2012/Summer2012.pdf, pg. 6). It was slightly edited and retitled for publication.
Why is planting native vegetation a good idea? We all know that native plants arranged in natural combinations and densities provide safety corridors for our native animals. San Diego’s plant communities have, like all established ecosystems, developed a symbiotic relationship with native and migratory fauna. Our plants leaf out, bloom and fruit when native animals and insects need the food, and provide appropriate nutrition that imported or invasive plants may not. Wildlife then disperses seed and pollen in methods that suit the plants, as well as providing the fertilizer for which the plants have adapted. Flora and fauna have set up symbiotic relationships to an extent where some species rely solely on a single other species for their existence. A balanced ecosystem is a dance between inhabitants who know each other’s needs and satisfy them for their own survival.
We plant natives in our yards because they are hard-wired for our soil and climate. They naturally conserve water and do not need fertilizer or insect control. They also can be beautiful. Planting native plants is good for our wallet, our resources and our health. But there is more to the equation. Living in every handful of good soil are billions of microscopic creatures and fungi collectively called microbes that make nutrients available to plant roots. The smell of fresh soil is a chemical released by these microbes called geosmin. Scientists now know that the microbes in undisturbed soils form a communication network between tree and plant roots. When a tree is attacked by insects, communication is sent out chemically by the tree’s roots and carried via this microbial network throughout the ecosystem, and other trees set up defense mechanisms to lessen their own damage.
Plants also communicate via scents not detectable by humans. Lima beans and corn planted downwind of brother plants which had been subjected to grasshopper attack lowered their sugar content to be less desirable. Such plants received 90% less insect damage than those planted upwind. California sagebrush (Artemisia californica) allows sibling plants to grow nearby because when attacked, it emits an airborne chemical to repel insects. The more sagebrush in the area, the better the protection as other sages respond in kind. Some plants when attacked will release a chemical that attracts the predatory insect which will feed upon the bug that is attacking the plant.
Thus plants communicate via airborne chemicals and through their roots via the microbial network. They call for help, they send out alarms and insect invitations and what’s more, they respond to each other. The why of planting natives is therefore also this: It is important to plant natives because they all speak the same language. Plants introduced to an area by humans are like strangers in a strange land. They cannot communicate well with other plants. They don’t know which bugs are bad until it’s too late. They have no one to call for help; the pheromones they emit are for beneficial bugs that live far away. Their seeds cannot supply the proper nutrition for the wildlife, and the wildlife may not be able to supply the plant with what it needs to keep healthy. They struggle to succeed in our soils and become stressed and sickly. We pour fertilizer and pesticides on them to help them survive, which kills the microbes that create good soil. Also, without the natural checks and balances found at the plant’s native ecosystem it may well become invasive and rob space, water and nutrition from our natives. The weeds you see in reclaimed properties are mostly non-native. Foxtails and wild radish do not belong here. Hike in some of the preserves which have not been previously farmed. There you’ll see the real native wildflowers, such as California peony, rattlesnake weed, tidy tips and Blue-Eyed Mary, living in harsh decomposed granite soils on little water, in relationships with the other chaparral surrounding them. You’ll understand a little more about how plants form guilds to support each other, and create that wholesome rightness that we feel when we walk in undisturbed nature. Recreating those guilds in your garden, adapted to provide human food, medicine and building materials, is called Permaculture.