Now, the United States produces more poinsettias than any other country, patenting new varieties and reaping about $260 million a year in sales. Mexico, on the other hand, can't sell the plants in the United States because of restrictions on importing Mexican soil.

"It's our plant, but now they have the patents and the name, too," said Diana Esquivel, financial manager of Finaflor Nurseries in Cuernavaca, 40 miles south of Mexico City.

The ban has been around for decades. It probably dates from the early 20th century, when modern quarantine laws went into effect. Meanwhile, poinsettia sales have been growing steadily in the United States: They rose from 56 million plants in 1992 to 68 million last year.

Arizona alone produces about 500,000 poinsettias a year and imports others from California and Utah, according to the Arizona Nursery Association. Mexican growers believe they can compete north of the border and even have their government's backing.

For now, the only nochebuenas that Mexico can export are green cuttings the size of toothpicks, which U.S. growers cultivate and turn into finished plants. Many of the big American nursery suppliers have operations in Mexico to produce cuttings.

A cutting costs about 10 cents, a finished plant as much as $15 in the United States. A similar plant in Mexico sells for $2 to $5.

"Just imagine how well we could do if we could sell these plants in the United States," Esquivel said as she strode through rows of fiery Freedom Reds, glorious Red Angels and speckled Gingerbells. "The Americans don't have big plants like these here. They would love them."

Officials at the Mexican Embassy in Washington think so, too, and have been lobbying the U.S. Department of Agriculture to allow in plants with artificial soil, either the vermiculite nuggets found in some potting soil or a substitute made of ground-up coconut shells. Both would be sterilized before being used for exports, said Enrique Lobo, head of agricultural affairs at the embassy.

"These are high-tech substitutes, and I think eventually they'll be approved," he said.

Mexico has a similar ban in place on imports of U.S. soil, probably as a tit-for-tat measure, some growers said.

Jose Luis Vega, owner of Dream With Colors Nursery in Phoenix, said he empathizes with Mexican growers but that American nurseries deserve credit for turning poinsettias into an industry.

"Henry Ford came out with the first Ford, but other people contributed to making cars better after that," he said. "The U.S. people have put a lot of research into the nochebuenas, coming up with all kinds of new colors and shapes."

Especially frustrating to Mexican growers is that Canada is allowed to export potted poinsettias to the United States. In 1997, the two countries began a joint certification program for greenhouses, making it easier for plants to move across the U.S.-Canadian border.