All the usual trappings of the White House Christmas were there yesterday: high-powered New York decorator Mark Hampton, 300 poinsettias, photographers and reporters knocking each other over to hear what new thing the First Lady had to say about the old holiday.

But this year, there also were differences. In the great hall were swags of green and Douglas fir trees. But there were no ornaments to hide the deep forest greens, no fripperies to obscure the strong white marble columns and the elegant architectural detail.

So when you stepped into the Blue Room, the eye was surprised and over-whelmed by the 20-foot-tall noble fir tree and its 2,500 ornaments. The decorations were made by retarded men and women, boys and girls, from all over America who have not often seen their handiwork so honored.

The ornaments vary in design and materials and in the skill and patience used to make them. There are an intricate piece of needlepoint; a colorful Eye of God made of yarn; styrofoam blocks in the shape of Swiss cheese from St. Francis Children's Center in Milwaukee, Wis.; paper cups with foil angels pasted on; peanut chains from Georgia; paper garlands; Mardi Gras beads pasted on a circle; sea shells gathered in North Carolina and Delaware; Hawaiian Hale Koa sea pods; pipe cleaners twisted into balls, a Jewish star made of yarn; a chicken pot pie plate fringed and centered with a picture cut from a magazine.

The ornaments were collected by the National Association for Retarded Citizens, which represents 6 million people in the United States, according to its president, James R. Wilson Jr.

Each person who made an ornament will receive a certificate, recording his or her contribution to the White House Christmas.

Mrs. Carter hunted for words to express her feelings that doing your best, no matter where on the scale of things your best is, can still be a contribution to the country. "We wanted to show," she said, "that retarded citizens have talents, and we recognize their right to develop them fully." And she held tightly to a star made of pipe cleaners.