Advice for gardening in Sonoma County’s ‘summer-dry’ climate

In the last decade, after years of drought and wildfires, Sonoma County has become a lot smarter about gardening.

Perennials and raised beds of food crops have taken the place of thirsty lawns. Grass is almost a dirty word. Savvy gardeners have increasingly turned to what many consider the perfect plants for the North Bay — plants for a Mediterranean climate.

But what exactly does “Mediterranean” mean? Are we talking Barcelona, Spain or Alexandria, Egypt? Palermo, Italy or Santorini, Greece? All have different microclimates and geography.

A more precise and helpful way to talk about smart gardening relates not to geography but climate. While there are regional differences, the Pacific Coast from Southern California to Vancouver, Canada has what’s called a summer-dry climate. Whether you’re in Seattle with an average of 38 inches of rain a year or San Diego, which gets an average of 12 inches, most of the rain you receive falls in winter.

This is helpful to keep in mind when choosing what to grow and where to plant it, says Nora Harlow, a landscape architect who for years worked for the East Bay Municipal Utility District. Harlow has collaborated with botanical photographer Saxon Holt on a handy new book, “Gardening in Summer-Dry Climates: Plants for a Lush, Water-Conscious Landscape.”

Many garden centers and nurseries are now labeling plants as drought-tolerant, low-water or California-native. But as with the term, “suited to a Mediterranean climate,” the description is not specific enough.

Diverse California climates

A plant may be drought-tolerant in one location but may need more water growing outside its native habitat. And California has many diverse climates and microclimates.

A plant along the North Coast that needs no water in summer may struggle in Sacramento, even with regular summer irrigation. And that same plant, grown in the shade and given ample water, may die. Many plants marketed as drought-tolerant may be native to the Southwest, where they are accustomed to an occasional summer monsoon.

“People need to know much more about where a plant is from. Where is it native to? What is the soil like? ‘Mediterranean’ or ‘native’ may be what the label says, but that doesn’t tell you anything about the plant,” she said.

Identifying a common “summer-dry” climate for the North Bay is not so easy either. Even within the region, there are many microclimates and soils.

“There is so much variety in Sonoma County that you could virtually go a block and find a different climate,” Harlow said.

She was turned on to the idea of summer-dry gardening while she served as supervisor of water conservation for the East Bay Municipal Utility District. That led her to see that the simplistic labels were not enough.

Native plants

Of course, if you’re working with true North Coast natives, you know your garden will be largely self-maintaining once the roots are established. Ceanothus, coffeeberry, currants, gooseberries, mahonias, monkeyflower, mock orange, silk tassel, toyon, wax myrtle, oceanspray and elderberry are some of the common native shrubs. Native trees range from madrone and buckeye to many oaks and pines.

But there are many other plants that are not native but still suited to our own particular variations of summer-dry climate, including many lavenders, rosemary, artemisias, grevilleas, rockroses, eryngiums, euphorbias, agaves and ornamental bunchgrasses.

So what are Harlow’s favorites? Manzanita is one. It requires hardly any water.

“I have an Austin Griffith” manzanita, she says, “that I haven’t watered in years.”

She also favors Matilija poppies for “a fast effect,” although be aware they can spread quickly.

Other favorites are sage, good if you have a deer problem, native grapes and sugar bush, which can grow to 12 feet, so it needs a bigger garden. But it also grows fast and is deer-resistant.

Harlow says she does not preach that gardeners use only natives. Gardeners must each decide how much time they’re willing to devote to maintenance, whether they are willing to let plants reach their full height and width and if they can tolerate the drab browns and grays of summer dormancy.

“My goal for a landscape is to make the garden as independent as possible,” she says. “If it’s independent, you don’t have to mess with it much. And if you don’t interfere too much and it’s successful, you’re blending into the native ecosystem. And you can’t do that unless you garden with climate.”

The fewer resources you use, from water to fertilizer, the closer you come to the natural landscape.

“It doesn’t mean you have to have all native plants,” Harlow says. “It just means the garden should function on its own more. And the clue to whether or not you are fitting into the environment is how much life you see. How many birds, how many insects, how many worms. It’s just obvious when you have life in the garden, and it’s obvious when you don’t.”

So when looking for plants to include among your natives, look for ones that will thrive together. And in this region, that means plants that are similarly summer-dry.

“If they like similar conditions, they will learn to live together,” she says. If you do want to incorporate some favorite plants that require more water, don’t plant them with your summer-dry plants and natives. Group plants together that have similar soil and water needs.

When you garden with climate in mind, you will be more successful, she adds. That includes incorporating design elements that support plants that don’t require much, if any, summer irrigation. You might consider adding a rainwater harvesting system. To avoid saturated soils, plant on mounds or in raised beds to guide runoff away from plants that depend on good drainage.

Harlow is concerned that fear of wildfire is prompting a lot of people to take out trees, denuding the landscape. The solution, she stresses, is to make sure your trees are maintained, that you’ve cleaned out the dead wood and that you’ve mowed dry weeds. Space out plantings and don’t plant anything that will burn next to your house. Design your landscape with paths, gravel and hardscaping.

Harlow and Holt have devoted most of the book to an extensive summer-dry plant directory with plants’ characteristics and water needs, illustrated with beautiful photos by Holt.

The idea is not so much to promote drought-tolerant gardens as climate-tolerant gardens that foster environmental resiliency, particularly at a time of climate change.

You can reach Staff Writer Meg McConahey at 707-521-5204 or meg.mcconahey@pressdemocrat.com. OnTwitter @megmcconahey.