Bill Ackerman stopped the car, let out a deep sigh and lumbered out into the warm breeze.

"Now you see why I've been wearing such a long face," he said. "This is it. Devastation Row."

He pointed to a descending hillside of withered shrubs, what was left of one of the most impressive stands of camellia bushes north of the Carolina.

"We always knew that Washington was at the northern edge of the camellia belt," he said. "It was always considered an area where six or eight varieties could survive. But over the last two decades we've had success with two or three hundred."

That success came to a sudden and sobering end in the brutal winter of 1977. The harsh cold spells of '78 applied the coup de grace.

Now the occasional healthy camellia stands out among the acres and acres of dead and dying ones at the U.S. National Arboretum off New York Avenue NE. It breaks the heart of Ackerman, the Arboretum's camellia specialist.

"We went strong for a while on fragrant strains," he said. "Now I suppose you'd have to consider that kind of a luxury. It you're going to lose them, who gives a damn about fragrance?"

He reached in and plucked a flower bud from a bush, opened it and pointed to the reproductive organs. "Burned, see?" he said. "The sex organs are the most susceptible to cold."

Ackerman is down today, but he'll be back up and planting soon. "It's our worst winter for camellias since the collection was started in 1947, " he said. "We'll just have to start all over. We're not quitting."

Bad news, but elsewhere on the exquisitely manicured grounds of the 450-acre Arboretum the story is happier.

Azaleas took something of a winter beating and a few magnolia tree were damaged by cold, but generally things are alive and thriving in this, the height of the season.

For those who don't know about it, the Arboretum is where Washingtonians go to celebrate spring when the tourists take over at the Tidal Basin.

It's hard to get to, but the scenery is awesome, the price is right (free) and the variety of flowering shrubs, trees and plants on the huge grassy tract keeps the high season thundering along through May.

According to the official data sheet, for example, we have the following to look forward to this weekend and next:

IN BLOOM THE THIRD WEEK OF APRIL:

Japanese camellias, daffodils, magnolias, forsythia, tulip, callery pear, Japanese quince, early crab apples, flowering cherries, azaleas, wildflowers.

FOURTH WEEK OF APRIL

Magnolias, crab apples, violets, azaleas, rhododendrons, daffodils, Japanese quince, wildflowers.

The chief attraction since the Arboretum opened to the public in 1959 has been the azalea hillside, acres on acres of mature, tightly packed bushes in brilliant colors. They should be sparkling this weekend.

Magnolias and dogwoods do well here, too, along the winding banks of the muddy Anacostia, and there are strange plots of decorative shrubs tucked around the grounds, a duck pond, formal gardens, a Japanese bonsai exhibit and a plethora of other good stuff.

The Arboretum is a project of the U.S. Department of Agriculture and paid for by your taxes, so stop wondering why you're getting something for nothing. About half a dozen USDA plant breeders like Ackerman use the facilities to experiment with new strains. In addition, there is a herbarium (a library of plant parts), an auditorium and a big staff of groundskeepers.

For years the Arboretum was Washington's hardest attraction to find, with the main entrance nestled at the corner of 24th and R Streets in far Northeast.

The magic route is north on New York Avenue, right on Bladensburg Road NE, then about three blocks to signs pointing to the turnoff onto R Street.

This year there's been a breakthrough, anyway. With the acquisition of 33 acres of an old brickyard, a path has been cut out to New York Avenue itself, and there's a new entrance on the avenue just north of the Bladensburg Road crossing.

Inside are nine miles of pleasant paved road with a speed limit of 15 mph, which really is faster than you'll want to go. It you've got a spark of life left you'll want to ditch the car and hoof it. Of course, it's an ideal place for gentle cycling, motor or pedal. A rule of remember, however, no picnicking.

Summer hours: 8 to 7 weekdays, 10 to 7 weekends.