by Nancy Wilson, U. C. Master Gardener
As we look forward to summer, we know it will be hot and dry, and many plants in our gardens will close down in the heat. Many of us have lived or traveled in places where it rains year-round, places with storybook seasons of winter, spring, summer and fall. Often we see plantings and garden ideas we want to reproduce in California. And just as often, we are frustrated by how poorly these selections do in our gardens.
Whether we want to admit it or not, our Mediterranean climate controls the success or failure of our gardens. We are wise to make friends with the dominant forces of our climate and use them to our advantage.
California is one of five areas in the world with a Mediterranean climate. The others are the Mediterranean basin, western South Africa, central Chile, and southern and western Australia.
These areas share roughly the same latitude. They receive relatively low rainfall, with most falling in the winter. They also have low summer humidity, which creates high sun intensity and high rates of evapotranspiration in plants.
Regions with so-called Mediterranean climates have moderate temperatures year-round. They enjoy the marine influences of their coastal locations. They also have rugged coastal mountain ranges parallel to the coastline, which influence and modify climatic patterns, forming rain shadows and microclimates.
These conditions describe the Napa Valley perfectly, but the Napa Valley is not homogeneous. Before you plant, check Sunset1s Western Garden Book to learn more about the characteristics of your particular climate zone.
There are four Sunset zones in our valley. Zone 17 experiences more marine effects. Zone 15 has chilly winters. Zone 14 is the warm coastal region, and Zone 7 is known as the foothill/digger pine belt.
In dividing the West into zones, Sunset considered many characteristics that affect the selection, growth and care of plants. Among these are latitude, elevation, ocean influence, continental air influence, mountains and hills, and microclimates. These features help determine which plants will survive and thrive in your garden.
You will want to do one more bit of research before you get out your shovel. Make a site analysis of your property to determine your microclimate. This working document indicates all of the pertinent features of your landscape. It shows buildings, elevation changes, wind direction, movement of the sun in winter and summer, deciduous and evergreen trees, shade, frost pockets and water courses.
Keeping track of high and low temperatures, frost dates and rainfall will help build a true picture of your property. Your analysis doesn't need to look professional; it is simply your guide to your garden.
Now you are ready to consider plant materials. You have enough information to begin putting the right plants in the right places, to consider hydrozones where plants with similar needs are placed together so that they are watered appropriately.
Mediterranean gardening is the logical, natural response to our climate. Learning to recognize appropriate plants for Mediterranean gardens will help you establish a sustainable, drought-tolerant, low-maintenance landscape. This doesn't mean you need to grow only succulents or forgo your favorite species. It does mean that you garden with our wet winters and arid summers in mind.
Our resources of water and energy are limited; that will not change. Can we learn to live with these constraints and still plant for diversity, habitat and interest? It may take a shift in our thinking and some practice, but the rewards will be beautiful.