Trees for the drought

Homeowners planning to reinvent their yards into less thirsty landscapes are now showered with ornamental choices, from intriguing natives to attractive Mediterranean plants. But you can’t design a good landscape on lavender and salvia alone.

Creating a yard out of only low perennials, without trees, is like furnishing your living room with small chairs and forgetting a focal point like a fireplace and sofa.

Trees provide both structure and shade as well as oxygen. Their blossoms, bark and leaves add texture, shape and color. They are an essential anchor in most good landscapes. But just as with any other class of plant, their water needs can vary widely. When putting together a garden of shrubs and perennials that will withstand low-rainfall years, gardeners would be smart to look also for trees that need minimal or no additional irrigation and will better withstand a prolonged drought.

“People just don’t understand trees. They’re afraid of planting them and yet they’re such a good thing,” said Sara Malone, a master gardener who professes to be “passionate about trees.” Her extensive Petaluma gardens feature a number of attractive, drought-tolerant trees.

Just because a tree is native doesn’t mean it’s drought-tolerant. Redwoods, for instance, have huge water needs and depend on fog to help them survive the dry months. Beyond the coastal zones, they’re not a smart choice. And they also grow way too big for the average city or suburban residential lot, said Malone, who is preparing to train other Sonoma County Master Gardeners about drought-tolerant trees. Many of the native oaks also will grow just too large for the average small yard. Instead, consider planting trees that will grow no more than 25 feet to keep them from taking over your yard and choose trees that don’t have big water needs.

Autumn is the best time to plant trees, as soon as the rains start, said Robert Kourik, a landscape designer in Sonoma County, who is a pioneer in low-water-use landscapes dating back to the severe drought of the 1970s. Even low-water-use plants and trees need irrigation to get established in the first couple of years. By planting in fall you can let Mother Nature do the watering for you.

“The roots will have all winter to grow because it doesn’t get cold enough to stop them,” said Kourik, who authored the book, “Roots Demystified.”

He maintains that by giving them just enough water in the first couple of years to get their roots established, they will be able to endure much less water going forward.

One tree that is at the top of many drought-tolerant lists is Arbutus unedo, or the strawberry tree, with a dark burgundy bark like manzanita, but bigger. It produces round, strawberry-colored fruit all winter.

“I planted mine in 1998 and it’s now almost 25 feet tall and has not been watered,” Kourik said.

Malone, who has put together a list of good drought-tolerant trees for Sonoma County for use by the Master Gardeners, said Arbutus “Marina” is also a great choice for a shade tree that provides year-round interest. It is a broad-leaf evergreen with has large, shiny leaves, pink and white flowers and red, orange and yellow fruit.

Another good shade tree that withstands drought conditions is the olive. Malone suggest a fruitless variety like Wilsonii or Swan Hill that won’t make a mess. For an attractive ornamental, the crape myrtle is almost foolproof and a mainstay of many a Northern California landscape. They come in a big variety of colors and burst into bloom in late summer, just as many other things in the garden start to fade.

The Laurus Nobilis “Saratoga” is a cultivar of the standard European laurel that is very resilient when it comes to water. Named after the California city of Saratoga, it produces yellow flowers in spring. But one of the toughest trees, a real survivor, is the Ginkgo biloba. A deciduous tree, the Gingkgo or maidenhair tree, comes in some nice landscape varieties like “Jade Butterflies” and “Chi-Chi.”

Other good deciduous trees for the water-wise landscape include the Chinese elm, the Western redbud with its showy lavender-pink flowers in early spring and the persimmon, which produces glossy leaves, fall color and bright orange, edible fruit.

James MacNair, an arborist and former Sonoma Valley nurseryman, was part of the original committee of experts who came up with the Water Use Classifcation of Landscape Species or WUCOLS for the University of California. Among his recommendations for low-water-use trees are the Chinese Pistache, the Catalina Ironbark, the Melaleucas or myrtles from Australia and the Oklahoma redbud, a very durable deciduous tree with bright yellow leaves in autumn and magenta flowers in spring.

When planting trees, or really any plant, it’s critical to group them by water needs or hydrozones, so you’re not over-watering some and under-watering others, MacNair says. With low-water-use trees, make sure anything you plant under them, including groundcovers, is also a water-sipper rather than a gulper.

Kourik recommends planting in mounds of approximately 12 inches high and 3 inches wide, so you get good drainage around the base. Take care not to make the planting holes slick on the sides; otherwise when they dry they will become hardened and difficult for the roots to penetrate. Instead, fracture the sides of the hole with a spading fork.

He plants in a hole just slightly wider than the root ball.

“I make a cone so I can spread the roots on the cone and then make a hole as big as that, or a little bigger,” he explained. “Then I put in native soil and no amendments. You want them to get used to the soil they have.” If you put too many amendments in the hole, he noted, the roots will want to stay there rather than spreading out.

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