A recent "sweep" in national forests in Idaho found illegal aliens working for the federal government as tree planters. Forest Service spokesmen claimed ignorance, but for Louise Brannon Wagenknecht, who worked as an inspector in the Klamath National Forest near the California-Oregon border from 1975 to 1987, the denials rang false indeed. Wagenknecht is now raising sheep in Idaho and writing for the "High Country News" a biweekly published in Colorado.

"The Forest Service does not knowingly hire contractors who break federal immigration and labor laws."

That was the prim official response to the recent roundup which caught illegal aliens planting trees in Idaho's Boise National Forest.

Maybe. But for more than a decade I worked in the Klamath National Forest inspecting crews who did the hard, dirty work of forestry -- and they were not only Mexican, but teenagers.

I've loaded bags of trees onto green pickups at 5:30 in the morning. I've led vans full of planters up muddy, winding, logging roads. I've looked out through clacking windshield wipers at a pie slice of forest -- a thousand foot long wedge with every living stick of wood removed or burned -- then stepped out into a crowd of about 20 planters, all Mexican, and most under 21, including a few who later told me they were 14. A few may have been even younger.

On a typical February morning, two foremen, the only English speakers, open the bags and lift out the bundles of tiny, two-year-old conifers. Planters seize the trees, slosh the roots in a slurry of water and vermiculite, then stuff them into rubberized bags belted to their waists -- each holding about 500 seedlings.

Some planters are relatively new arrivals -- they wear cheap tennis shoes, polyester trousers, loud cowboy shirts but no gloves or hats until they get their first paychecks. It's 34 degrees, windy and raining -- cold even through my long underwear and heavy raingear.

Once their bags are full, the young men drop out of sight -- the earth falls away from the road in a slope steeper than an attic staircase -- and work down the hill, eight feet apart, searching for planting spots.

Their only tools, "hoedads," are flat steel blades about 18 inches long and four inches wide attached to ax handles. They plunge the blade into the soil, pop the handle to break a space, deftly slip a seedling in, tamp the soil, and slide another eight feet down.

At midday, the crew builds an enormous fire on the roadbed to brown tortillas and fry meat and beans. Peppers, salsa, cans of soda and cookies appear and disappear amid talk and laughter. Their lives have given them rough hands and whippet-like bodies, but they seem happy at the prospect of three months of picnics in a deluge.

We didn't ask questions, but actions spoke. One day, when a Forest Service expert paid an unannounced visit in his personal truck, the crew dropped tools as one man, and raced off. The two foremen, legal and middle aged, came up the road -- and laughed in relief.

"Your truck," they chortled, "is the same color as the Border Patrol trucks. You scared them pretty good!"

Real immigration raids usually came at night, when the crew was asleep in rented motel rooms in town. For us inspectors, this could mean a welcome rest -- but it could obliterate years of work by the nurseries that grew our seedlings.

Once 80,000 seedlings arrived by truck on the morning after a raid, and had to wait with hundreds of thousands of others in a tree cooler for a month while the planters made their way back north.

When they came, they put in 14 hour days, seven days a week -- planting as many as 23,000 trees a day -- but time was against us. A week of hot weather in early May ended the season. We waved good-bye to the crew, and set fire to the hapless leftover trees.

How did the federal agency get itself into this shadowland of illegality? Blame it on projections that large clearcuts could be successfully regenerated with this wholesale approach. In reality, planting, unlike logging, cannot be mechanized on the steep slopes of the Pacific Northwest.

We had to plant 1,500 acres every spring, and this meant we had to have large crews. Local people may have wanted the work, but they lacked the cash to compete for the huge contracts put out by the service.

So each winter, Forest Service contracting officers sitting in warm headquarters buildings solemnly told the successful bidders -- big labor contractors with access to the Sacramento-San Joaquin Valley's very large reservoir of undocumented laborers -- that hiring illegal aliens was, well, illegal.

Contractors solemnly assured the officers that all their workers had green cards.

The officers, paperwork in order, went back to their desks.

And 70 miles away, a couple of inspectors followed two dozen ill-clad teenagers across a scarred mountainside.

We watched the road above, yelled "Bueno!" down the slopes, and silently prayed that these cheerful and competent youngsters would not be disturbed until they had crawled out of the last clearcut and planted the last tree.