Southern California has a wonderful climate, suitable for growing plants from many places around the world, and many exotic plants do grace our current city landscapes. What Southern California doesn't generally have, tho, is enough rainfall to support these introduced plants. We've gotten used to supplying additional water to our roses, begonias, magnolias, and lawns. It's become increasingly clear over the last decade or so that human populations are increasing at the same time that the amount of water available to us is decreasing, and that therefore our habits simply have to change. Reducing the amount used in gardens, and using every drop efficiently are clearly important.
1) Substitute areas of concrete, pavers, decomposed granite, bark, leaf litter, gravel, river rock, tumbled glass and so on for plants. However, green is more restful to the eye and soothing to the nerves, not to mention more in keeping with the character of Claremont, so this should be done with caution and with good design in mind. Sustainable Claremont is assembling weblinks and a photographic archive of good examples of integrating plants and hardscape.
2) Increase the proportion of drought-tolerant plants. Nurseries can help with this; sunset.com (native and exotic), rsabg.org (California natives), theodorepayne.org (California natives) and sustainableclaremont.org (local natives) all have helpful information. We are not actually a desert (look at the Bernard Field Station to see what our native plant cover looks like) so restricting your plants to agaves and cacti is neither desirable nor necessary.
3) Group your plants in 'hydrozones' according to their water needs. This allows you to design an efficient irrigation system and to make sure that all plants in an area get the water they need and no more. Small lawns can be useful, look good and still be water-wise. Look for varieties of grass that are drought-tolerant. Artificial turf is generally not a good idea (more on this another time).
4) Encourage deep roots. If plants are watered a little each time, roots tend to stay near the surface and dry out due to evaporation from the soil. Watering longer and less often will encourage deeper root growth. However, if you water too long most of it will rapidly drain away. In our sandy loam, water tends to move down rather than out. It's a good idea to dig down in the soil after watering and see just how deeply the water penetrated so you can adjust the time.
5) Design your irrigation system to apply water close to the root zone rather than spraying it high into the air where much will be lost to evaporation. Drip irrigation, soaker hoses, popups all have their uses (and their problems). Water during early morning so evaporative loss will be low, and so the leaves will not stay wet for long which encourages mold. Turn on the irrigation by hand when the plants look like they need water and use a timer to shut it off. If you go for an automatic system, buy one with sensors that will not turn on if it is raining. Adjust the system so it doesn't water the sidewalks or cause water to run down the street.
6) Mulch (lay bark, straw, leaf litter, gravel, etc) between plants to reduce evaporation.This also reduces weeds which compete for the water. If you use a weed cloth under the mulch, be sure it allows water to percolate through.
7) Reduce fertilizer use. Most plants do just fine without it and they will use less water if they grow slowly.
8) Support wildlife with small ponds, recirculating fountains, or birdbaths, and choose plants that provide shelter, nesting space, and food. The increase in beauty and biodiversity is worth a little more water.
9) Growing food plants, including fruit trees, generally uses a fair amount of water, but the advantages often outweigh the costs. Water use in the rest of the garden can be adjusted to compensate, or crops can be integrated into garden beds with other plants that have similar needs.
10) If you are working with an existing garden, take stock of what you have and identify the water needs of the different plants. If high and low water-need plants are mixed throughout, move some, take some out, or replace them with different ones as the originals die. Make a plan for changing your garden and work towards it bit by bit.
Even small changes can have big effects. To get more information on irrigation and waterwise gardens, please come to Sustainable Claremont's Dialog talk on Waterwise Gardens and Irrigation Aug 2, at 7 pm in the Hahn Building at 420 N. Harvard Ave.
Demystifying Sustainability is an initiative of Sustainable Claremont (sustainableclaremont.org).