On the Road : Some Facts About Those Highway Trees, Shrubs, Plants

Here are some questions put to the California Department of Transportation about the foliage along the freeways in North County.

Just whose idea was it to plant trees and shrubs along the freeways?

The trees and shrubs you see along North County’s freeways today are the products of the vision of a woman in the White House 25 years ago.


Making America’s highways more aesthetically pleasing was the pet project of former First Lady Lady Bird Johnson. In 1965, she launched the Highway Beautification Act.

The act was intended to stop the proliferation of billboards along federally funded highways and in their place plant trees. Her effort included native wildflower seeding and it evolved into the planting program California has today, said Roch Scouton, associate landscape architect for Caltrans.

Trees and shrubs also provide glare protection against oncoming headlights, Scouton said, but they are not planted as safety barriers, he said.

Because of drought 10 years ago, Caltrans began gradually cutting back on the amount of ground cover it planted.

Which freeways have what?

Oleander--which requires virtually no water and flowers throughout the year--is a prominent plant along Interstate 5.

Ornamental plants such as ivy, ice plant and African daisies act as ground cover. Coral and eucalyptus are the only trees along I-5, Scouton said.

Native plants such as the rhus shrub and prostrate acacia serve as ground cover along Interstate 15, Scouton said. Both require significantly less water than ice plant.

In the northern region of I-15, the Heteromeles shrub can be found. Also north of Escondido, in the less densely populated areas, native sycamores and oak trees begin appearing.

Very little planting has been done on California 78 because of the major widening project under way. A few eucalyptus and some scattered pine trees are being removed tree by tree to make way for the widening but will be returned after the freeway project is complete.

California 76, also under construction as a connector between I-5 and I-15, has had sporadic planting. Shrubs and trees vary from community to community and depend on the intensity of traffic and visibility to motorists.

Native vegetation such as rhus, heteromeles, oaks and sycamores appear along California 52.

What water conservation measures are being taken?

Scouton said Caltrans uses reclaimed water from two sources: an aquaculture plant in Mission Valley supplies portions of I-8 and I-15 in San Diego, and reclaimed water from the Fallbrook Sanitary District supplies I-5 from Hill Street in Oceanside south to Palomar Airport Road. When the Encina sewage treatment plant comes on line next year, reclaimed-water coverage will extend further south, said Scouton.

Reclaimed water in North County now accounts for about 20% of the water used to irrigate roadside foliage, said Tom Ham, district landscape architect for Caltrans. About 300,000 gallons of water is used monthly in North County, he said.

How often is the foliage watered?

Watering schedules differ widely, depending on the landscaping, said Merl Nusz, Caltrans region manager. Some watering systems are turned on manually, but most are on automatic timers, Nusz said.

Countywide, Caltrans stopped watering in mid-February and will not resume watering until April 15, said Ham. Recent rains, although not enough to make a major dent in the drought, have saturated the ground enough to provide “a little savings bank” during these cooler months, Ham said.

Areas covered by reclaimed water, however, are still being watered, said Ham.

For the last two years, Caltrans has continually tried to cut back on watering while still providing enough for the plants to survive, Nusz said.

Because of strict conservation measures, water use is about two thirds less than what it was in 1989 and about 40% less than what was used in 1986.

“We’ve always been able to cut back 10% and sometimes more, depending on the weather,” said Nusz. “We ask our supervisors to look at their sections, ask them how they can cut back.”

“It’s not just this crisis, we’ve been doing that for three or four years now,” Nusz said. “But we’ve never been in a crisis like this, and we need to set some priorities.”

What happens when freeway foliage dies?

“We’re presently under the direction of not replacing a plant that is lost due to infection or lack of water,” Nusz said. “We haven’t replaced any plants for a considerable amount of time.”

Is there anything the average citizen can do to preserve the freeway foliage?

Maintenance crews, responsible for the landscaping as well as the road signs, cannot be in all places at once, said Nusz. Motorists who notice something awry with the watering system, such as a sprinkler spraying onto the roadway, are encouraged to report it to Caltrans, he said. The number to report wayward water is 688-6699.

“We want to do everything we can to make it aesthetically pleasing to live here and conserve what we can,” Nusz said. “We’ve done it in the past, and we’re going to have to do more in the future, but I know we can.”