This landscape displays California native plants from an assortment of regions throughout the state. Gardening with native plants saves water, energy, effort, and money (no mowing, limited fertilizer, reduced irrigation, etc.). Incorporating plants from your local region integrates your personal space into the surrounding ecosystem increasing your garden’s habitat value. Traditional cultivars found in most plant nurseries are domesticated species collected in the wild from various regions throughout the world. Through time, desired traits have been selected by plant breeders and are now a staple in the landscaping and horticulture industry. Albeit, these florid traits often come with a price (excess water, nutrient demands, etc.), providing minimal contribution to the surrounding ecosystem. We have finally reached the era of integrated gardening; utilizing a region’s innate environmental conditions to create a garden that is most suitable for the locale. It is at this time that California’s native flora is beginning to receive the attention, admiration, and respect it deserves. This section of the Landscape Learning Laboratory is an eclectic mix of plants, from throughout the state, worthy of celebration and display in your garden for various landscaping needs (shade, full sun, dry soil, lawn alternatives, etc.)
Fig A: Fremontodendron californicum, California Flannel Bush
California Native Gardening
Second to habitat destruction, invasive plants are the greatest threat to biological diversity today. Not only do invasive species pose as a significant ecological threat, California alone spends eighty million dollars every year fighting invasives that have now become a significant economic complication. Invasive plants increase the potential for wildfire, displace native plants that form the basis of productive ecosystems, and even clog valuable waterways. When invasive species establish in a new location, the pathogens, predators, and other limiting agents that control the population’s growth in its endemic region are not present. This renders an exposed region extremely vulnerable to the introduced species. It is estimated that roughly half of California’s invasive species are of horticultural origin. Supporting nurseries that are taking a leap in the direction of non-invasive gardening is an imperative to winning the battle against invasive ornamental plants.
Aside from the economic and environmental impact of introduced species, fighting the battle against invasive plants has a number of benefits for the gardener. Native plants are adapted to our climate, thrive in a variety of soils and require minimal care outside the realm of the soil food web (Section III & IV). California’s Mediterranean climate (wet winters followed by long, dry summers) has imposed a severe selection pressure on our plants. Species found in our state thrive in these rough conditions that demand a great deal of resources for non-natives to survive in. In addition, planting natives from you local region encourages native fauna to visit your landscape, improving your garden’s habitat value.
Employing the Soil Food Web
For numerous reasons, fertilizers have been a hot topic in recent decades. Agricultural processes are now common interest and techniques employed by industry are under public notice. For good reasons, people are now taking an interest in how plants are grown! The term organic is commonly thrown around and has various meanings among different groups. In the gardening world, one who practices organic techniques utilizes resources derived from natural sources (compost, wood chips, worm castings, guano, rock phosphate, bone meal, seaweed, etc.) rather than industrially processed fertilizers (Haber-Bosch process, and Odda Process) that have miraculously ensured access to crops for our steadily growing population.
Fig B: Simplified schematic of the Haber-Bosch process
A respect for the soil food web is the foundation of many organic gardening techniques. We know that plants hold and accumulate nutrients in their cells throughout their lifespan. When a plant dies, what becomes of these essential nutrients? Eventually soilborne microorganisms (bacteria, fungi, protists, etc.) consume this decaying plant matter. These nutrients become locked up inside the bodies of decomposers in a process called immobilization. Subsequently the decomposers themselves die, later consumed by other decomposers, or are eaten by larger organisms, like nematodes and earthworms that produce nutrient rich excrements in a process called mobilization. This continual process of immobilization (locked up) and mobilization (released) of mineral nutrients create the fertile soils that yield healthy and nourished plants. The beauty of this cycle is that nutrients are held within the soil. Unfortunately, rather than being immobilized, synthetic fertilizers drain through the soil and leach into the water table producing an adverse effect on the surrounding ecosystem. In addition, synthetic fertilizers destroy the soil food web. These fertilizers are incessantly mobilized, unable to be taken up by microorganisms, and form an osmotic potential between the microbial cell and the nutrient solution. This osmotic potential ruptures the walls of these single celled organisms voiding the soil of life.
Fig C: The general flow of events in the soil food web. Essential nutrients are immobilized in each trophic level
Alternatives to Fertilizers
The gardener’s role is to aid the soil food web and provide microbes with a steady food source to keep the immobilization/mobilization cycle continuing. The following techniques are employed to ensure the health of a well-balanced soil food web:
1) Composting: Decaying plant matter is rich in mineral nutrients and active microorganisms. Compost provides a “microbial boost” to soils.
2) Teas: In addition to traditional composting, it is becoming increasingly popular to create liquid compost teas. Applying the solution to soil boosts the microorganism count significantly and drastically revives the life in soil. These teas are often sprayed on foliage and defend the plant by competing against harmful pathogens.
3) Mulching: Various sources of plant matter (wood chips, leaves, etc.) is applied to the soil surface providing moisture retention, weed inhibition, and the soil food web with an energy source. Mulch also contains nutrients that enter the immobilization/mobilization process and enhance soil fertility. This process takes place over time and acts as a time-release nutrient source!
Employing these three techniques will form the basis of a sound organic gardening regimen. This is an incredible dynamic niche of gardening that continues to grow through new and innovative techniques from passionate individuals determined to change the way we look at plants.
-Cultivar: a plant species grown in cultivation and modified via selective breeding for desired traits.
-Endemic: a species that is unique to a defined geographic region.
-Habitat value: the degree to which your space contributes to the surrounding ecosystem.
-Horticulture: science, technology, and business involved with cultivation of plants for human use.
-Immobilization: mineral nutrients held in the body of a soil food web organism.
-Microbe: An abbreviated form of microorganism (bacteria, fungi, protists, archaea, etc.).
-Mobilization: mineral nutrients in a free-state and present in the soil solution.
-Osmotic potential: the drive of H2O molecules to move from a less concentrated solution to a more concentrated solution.
-Selection Pressure: the driving force of evolution and natural selection; any phenomena that differentially alters the reproductive fitness of a population.
-Trait: a variation of an observable character (leaf shape, flower color, plant height, etc.) in a given organism.
Species on Display
- Peter Raven, Ray Evert, and Susan Eichhorn. Biology of Plants. Sixth. New York: W.H. Freeman and Company, 1999. Print.
-Calflora: Information on California plants for education, research and conservation.
[web application]. 2008. Berkeley, California: The Calflora Database [a non-profit organization].
Available: http://www.calflora.org/ (Accessed: Oct 20, 2008).
-All photographs: Creative Commons Attribution