7. Mediterranean Climate Plants

I’ve already talked about using California native plants as a major step in creating a sustainable garden.  But there is larger category of plants that have many of the same benefits – those of the Mediterranean Climate Zone that California is a part of.  Although you won’t be replicating native habitat and providing that native sense of place I mentioned before, you can still conserve water and have a low maintenance garden.  Since conserving water is really the most important thing you can do to make your planting sustainable, you can work with this larger palette of plants and find unique flower colors, interesting bark and branching patterns, and even a few that thrive in tough urban situations.

What is the Mediterranean Climate Zone? 

The Mediterranean Climate Zone covers a relatively small amount of the planet, compared to the Humid Subtropical and Humid Continental climate zones that dominate some of the most populated parts of the world.  The places with a Mediterranean climate are found in both the northern and southern hemispheres in the same horizontal band across the planet, the latitude range of 30 to 45 degrees.  They tend to be western coastal areas where the sea serves to moderate temperature and high pressure systems dominate in the summer, keeping rain systems away.  This climate zone naturally includes the coastal areas of the Mediterranean Sea, from Spain to Greece, Turkey, coastal Lebanon and Israel, and the northern edges of Morocco and Algeria. The California coast is the other major Mediterranean climate area in the northern hemisphere, including parts of Baja and Southern Oregon.  In the southern hemisphere the central Chilean coast, the southern tip of Africa, and the southern coasts of Australia and New Zealand fall within this zone – see this link for a general map: http://en.wikipedia.org/wiki/File:Medclim.png

The dominant feature of the weather in these places is the warm, dry summer where literally no rain may fall for a period of 6 months or more.  Typically the winters are wet and mild, rarely producing hard frosts.  Several of these areas rely on nearby mountain ranges to accumulate snow and send it down in rivers and streams in the spring.  But the primary growing season in Mediterranean climates often starts in what we normally call winter, because it is not too cold and the rains have begun.

Common Plant Characteristics 

The common climate of these far-flung places means that the plants also have certain characteristics in common – they all evolved to survive in similar weather.  In order to make it through the long periods without water many of these plants have narrow, leathery evergreen leaves that are often aromatic, such as the Rockroses (Cistus species) native to the Mediterranean Basin, or even needle-like leaves such as the Grevillea genus of plants from southern Australia.  With less surface area, these types of leaves lose less water to evaporation. Other plants have adapted to produce a wide variety of leaves on a single plant, according to the exposure.  For example, the California Coast Live Oak (Quercus agrifolia) can have larger thinner leaves in the shade and small thicker leaves in sunnier portions.  Late-summer dormancy is another thing you see, with plants either dropping most of their leaves or producing fewer and smaller leaves in the latter months of the dry season.  The California Buckeye (Aesculus californica) is a classic example, which has leaves that yellow and drop off in mid-summer, sprouting new ones around February.

Regional Variations

Of course all of these places don’t have exactly the same weather, and other environmental factors can vary quite a bit.  In my experience there is one aspect of many parts the San Francisco Bay Area that differs from other Mediterranean climates: the dense clay soil. Quite a few of the interesting plants from these other places are accustomed to rockier, better draining soil, and can be tough to keep alive in the ubiquitous clay around here.  For example the Protea family of plants from South Africa has some really interesting looking shrubs, but most of them need very well-draining soil to thrive.

Another time, I’ll get into strategies for dealing with clay soils – including plant selection and soil amending.  But for now, take a trip to the nursery or the botanic garden and check out the interesting plants from other places with a Mediterranean climate.  Just be sure before you buy anything (as always) to double check that it is appropriate for all the micro-conditions of your garden.

References:

Plants and Landscapes for Summer-Dry Climates, published by the East Bay Municipal Utility District

California Native Plants for the Garden, by Bornstein, Fross and O’Brien