Choice young trees add the final touch to a $5.5 million transformation of Brookside Gardens in Wheaton. (Adrian Higgins/The Washington Post)

Creating something as prosaic as a parking lot has been thought of as the realm of the engineer rather than the designer, and certainly not the gardener. But botanical gardens are beginning to see that the place you leave your wheels is not secondary to the garden experience but the first part of it.

It should be an environment where plants — especially trees — can be used to announce their institutional importance. Once this shift in thinking occurs, the possibilities are boundless.

At Brookside Gardens in Wheaton, Md., the long-awaited opening of the new arrival area and parking lot — two years in the making — offers another prime example of how these spaces can be transformed into something special.

The four-acre site runs between a woodland and a lake and connects Brookside’s visitor center to its entrance off Glenallan Avenue. The $5.5 million Gateway project, which includes $772,000 in donations, fixes the inadequacies of the old entrance and lot and achieves a great deal aesthetically, environmentally and programmatically.

From a practical standpoint, it increases the number of parking spaces by 50 percent, improves vehicle flow and allows a new arrival court to double as an outdoor event space. Those who look will see the type of sophisticated storm-water management system that has come to replace the woeful detention ponds of the past. In this project, that includes basins of flora that will take inundation, and large areas of permeable pavement atop highly engineered drainage layers.

A rarely used Hungarian oak is among the special plantings in the parking lot. (Adrian Higgins/The Washington Post)

At the edge of the existing woods, a retaining wall was constructed to reshape the sloping land. A stone wall would have cost too much, and a concrete wall would have been too plain . The solution was a gabion — rubble from the demolished lot pieced together with the care of Italian marble and held in a wire frame. “People are not used to building something like this; you have to push and persuade,” said landscape architect and project manager Ching-Fang Chen. Chen, who works for Brookside’s parent agency, the Maryland-National Capital Park and Planning Commission, has sought to implement high-design concepts in an economically challenged environment.

At Brookside, where the entrance garden was opened this spring, some areas are still unplanted. Design upgrades and construction issues ate into the plant budget, so the plantings are being installed small and in stages. No big, instant garden. This is all to the good.

“Now we have control over the quality of the plants and the plantings, and we can bring them on line and tweak them a little bit based on what’s happening,” said Stephanie Oberle, Brookside’s director. Most of the plants are being raised in-house, at the commission’s own Pope Farm Nursery . Oberle has relied on an army of volunteers to install plant plugs — 3,500 perennials in one push by Marriott employees.

The trees that now form a young canopy across the four acres are of species that are choice and deserve better recognition and general use. Red maples and crape myrtles are fine trees, but let’s start planting other species.

I asked Oberle and Brookside’s veteran plant curator Phil Normandy to show me the choices that the horticultural team settled on. I think I liked them all.

“This was a great opportunity to expand our plant collections,” Oberle said. The idea was to extend the spirit of the woodland into the new garden.

“The woods are strongly yellow in the fall,” so many of the trees were selected for their golden coloration, Normandy said. “We’ve used eight species of oak.” The choices include the chinquapin oak (Quercus muehlenbergii), the swamp white oak (Q. bicolor) and the hybrid selection Clemons (Q. x macdaniellii). “We have also used a lot of nyssa,” Normandy said. The nyssa, or black tupelo, is a handsome native tree that takes moist soil and is ablaze with color in the fall. The trees here include the variety Wildfire, selected for its autumn hues of orange and yellow.

The littleleaf linden is a great street tree, but the Brookside project relies instead on the far more special silver linden, whose heart-shaped leaves flash in the breeze. The underside of the leaf is a light gray-green.

On a lower bank, we have forsaken the Heritage river birch (hooray) for a birch hybrid named Royal Frost, with purple foliage, gold fall color and a gray-white bark. It’s at its southern limit here, so we’ll see how it does. Move toward the entrance, and you find a lawn that will be replete with bulbs. Nearby, visitors will find a collection of magnolia trees.

The horticulturists, including gardener Christopher Elenstar, have also picked uncommon choices for the avenues of trees. These include the American yellowwood variety Perkins Pink (the blooms are pink rather than cream) and Persian parrotias, which I have never seen used this way before. The key was to find single-trunked specimens rather than multi-trunked versions, and the variety of choice was Vanessa, more columnar than the species and a vivid yellow in the fall.

If there is one sylvan star, it’s the ginkgo. A row of male clones (no foul fruit) is found alongside the entrance, of the columnar variety Golden Colonnade. Next to the building, Normandy plans to nurture espaliered versions.

The project represents the first two of 15 phases of a master plan that seeks to shape the garden’s future. Brookside opened in 1969 and at first drew about 30,000 visitors a year. Now the number is approaching half a million. It has become a vital green oasis in the midst of a dense suburban area, and used by young and old alike.

I like the Gateway project for the way it telegraphs to people that this is how you make a garden. You construct all the necessary infrastructure and give the plantings a solid frame, and then you fill in with plants, slowly, patiently. You wait for trees to grow and form a leafy canopy. This may seem obvious, but there is a whole subset of horticulture feeding oversize trees to rich and impatient people who want instant effect. They are denying themselves one of the most magical elements of garden-making: the effect of time.

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