They Wanted the Greenest Property in America.

When management consultant Linda Yates and her Silicon Valley venture capitalist husband Paul Holland decided to build a new home on the same Portola valley, California hillside where Yates had grown up in a conventional ranch-style house, the couple made a momentous decision: that residential property—inside and out—was going to be green to the max.

Yates and Holland, though, are hardly granola-crunching, Birkenstock-wearing, Grateful Deadheads.

They’re hard-nosed businesspeople on an educational mission. They named their new home Tah.mah.lah, from the Ohlone Indian name for mountain lion or puma. The home is intended to be an instructional showpiece of the latest in green thinking and technology.

Down came the ranch home. Up went a project that turned out to have the highest LEED rating of any residence in the country.

When construction began in 2009, media stories focused on the buildings, with their recycled materials, solar panels, geothermal cooling and heating, and the energy efficiency.

Largely overlooked were the green-to-the-max, in-harmony-with-nature landscaping and hardscaping. The outdoor work is instructive to anyone in our industry.

Landscape architect Thomas Klope, of Thomas Klope Associates, East Palo Alto, California, was in charge of the exterior design. Ivy Munion, of ISC Group in Livermore, California, handled irrigation planning, while other contractors worked on wastewater treatment, stormwater collection, and the actual installation.

“The landscaping started with something unique— a set of green goals,” remembers Klope. “Everything we planned for the landscape went through the prism of those unchanging goals. Is it natural? Is it native? Will it regenerate? Does it use the minimum of natural resources and water? Does it recycle what can be recycled? Is it functional? Is it ‘local’?” The landscape team started by taking stock of the hillside, which they discovered was an intricate set of three mini-environments.

“We had three prominent landscapes,” Klope explains. “Redwood, oak woodland, and savannah grassland. Our mission was to design something beautiful, protect the plant material and native trees, remove that which wasn’t native, and irrigate it all with the minimum amount of water possible, since municipal water would be just for domestic use.”

The first thing to go was a conventional lawn, says Munion. “Conventional lawns suck up too much water, and we wanted to irrigate via subsurface drip.”

Neither Klope nor Munion were happy with the varieties of sod that were on the market. They were either not native to California, needed too much water to thrive, or both. Rather than settle, they talked to Delta Bluegrass, a commercial sod grower based in Stockton, California.

They asked Delta whether they would be willing to consider creating a new kind of sod specifically tailored to Tah.mah.lah’s south-facing micro-clime, but which would also be available for sale to others.

Jodie Sheffield, consultant with the company and chief specialist for research and development, recalls the process. “The first step we took was test plots at the property. We tried to germinate a California oak grass Danphonia, and a red fescue grass, Festuca rubra. We planted and observed over a six-month period. I remember that the Danphonia took three months to germinate, compared to its normal 14 days,” Sheffield remembers. “After six months, the stand was questionable as to whether we could lift the sod.”

“Meanwhile, we were developing other native grass species in sod form, and had nurtured a lawn alternative called Agrostis pallens, which is a native bent grass that’s also called “thin” grass. It has a fine texture and is a monostrand, so it looks like a conventional lawn. It also consumes at least 50 percent less water than conventional lawns, and possibly even more.”

Agrostis pallens was not used everywhere, explains Sheffield. “Where they’re not mowing the turf, we put in a mix of native grasses that top out at 18 inches before the blades tumble over on themselves. That mix consists of Festuca idahoensis, Festuca rubra, and Western Mokelumne fescue, Festuca occidentalis. It’s all irrigated with pop-up risers that get above the tallest grass; when the grass grows high enough to tumble, it forms almost a wavy green grass sea.”

To get a better sense of what the hillside looked like over the years, the design team took advantage of some aerial photography that had been done since the 1930s. For the other two terrains, Klope left in the native trees and plant materials and replaced non-natives with natives.

A sophisticated stormwater and wastewater collection and storage area has been built at Tah.mah. lah. Stormwater is gathered in a 50,000-gallon underground cistern. Darryl Jessen, president of Battle Mountain, Santa Cruz, California, who installed the system, explains that wastewater is streamed to underground treatment “boxes.”

Those boxes turn out reclaimed water pure enough to be used for watering the landscape.

“We installed a two-wire irrigation system. The two-wire reduced copper content on the property by 75 percent compared to conventional irrigation,” Munion says. The irrigation pipes are 100 percent recyclable, with compression-fitting high-density polyethylene.

The main lawn is irrigated via subsurface drip. Munion made provision for fertigation through a “compost tea” delivered by way of the drip lines. In-ground sensors feed information to a central controller that connect to an overall water/energy “dashboard” located in the home. That dashboard provides Yates and

Holland with real time energy and water status monitoring. It’s the best way to verify where and how electricity is being used, and whether water is being collected, stored, and delivered effectively.

Hardscaping went through the same green prism that guided work on the landscape. Out went the existing asphalt driveway. In went a driveway of porous crushed local stone, bordered by plant material native to the area.

On a business trip for an unrelated project, Klope discovered some huge abandoned limestone blocks that were literally gathering dust. He had those shipped in and placed artfully on the property.

Even wildlife was taken into account. Before construction began, biologists did an inventory of all native biological animals in the area.

The goal was to preserve and facilitate their native environments.

Klope points out that the planning process required a willingness to challenge conventional “green” wisdom with cold local facts. “We went in assuming that one of the landscape features would be a green roof on the home. After all, green roofs are the latest and greatest in absorbing rainwater, and providing insulation.”

However, once the the planning committee determined the energy load for the property and how energy efficient the home would be, there was no need for that design element. Standard roofing plus solar collection panels made more sense.

There was a similar experience with the swimming pool. Conventional wisdom was that a pool that filtered its water through a bog would be “greener” than a pool with traditional filtration, but energy models for the particular property showed that was not the case. A pool with conventional filtering made more sense.

The late Robert Kennedy said, “There are those who look at things the way they are and ask, ‘Why?’ I dream of things that never were, and ask, ‘Why not?’” Yates and Holland succeeded at Tah.mah.lah by asking, “Why not?” When you’ve got a new landscape project, why not suggest that it might be green to the max? If the customer isn’t ready to go all-in, why not make part of that landscape green?

Why not, indeed.