SAN MARCOS - On 200 rolling acres, the employees of Altman Plants toil and plan in January so that the poinsettias people buy in December and take home to their families are in full, vibrant bloom.

This is far from Altman Plants' top moneymaker - in fact poinsettias make up less than 1 percent of the company's total annual sales, according to Erin McCarthy, sales vice president. But it's a major undertaking, and one that would leave mantle pieces and dinner tables less festive had it not done.

It's been a banner year for Altman, which supplies customers like Home Depot, Target, and Wal-Mart.

"They're our primary customers for poinsettias," McCarthy said. "We've sold to all of them for years - and we're selling more to them this year."

In addition to its San Marcos facility, Altman runs a 400-acre operation at Lake Matthews in Riverside County.

"We're a full-service nursery," McCarthy said. "We supply annuals, perennials, herbs, vegetables. We're also the largest cactus supplier in North America."

But the focus for now - and for the next few weeks - is poinsettias. McCarthy expects Altman to sell about 700,000 potted "units" of Euphorbia pulcherrima this year, and a quick tour of one of the many greenhouses that hug the dusty hillsides is enough to leave a visitor overwhelmed by the sheer volume of scarlet on display - enough to fill 1.5 million square feet of greenhouse space.

Walking through them is one of the activities McCarthy likes best.

"I go in and I watch the plants, I report to our customers how the crops are looking, (and) I take tours with our customers," she said. "Michele got a great compliment from Wal-Mart last week; (their representative) said she had the best crop in the country."

The Michele to whom McCarthy refers is propagation manager and grower Michele St. Amant, now in her ninth year at Altman. As does McCarthy, she likes going through the houses - but she also confesses to bouts of anxiety, knowing that the success of her crop rides on many variables - chief among them the weather.

"Bright light during the day is gonna help enhance the color and bring it red sooner," she said. "That sometimes can be good or bad."

San Diego's recent heat spell, for instance, brought some of her plants to bloom prematurely.

"We did have some plants that were finishing a little bit sooner than we had hoped, but we were able to hold 'em," she said. "It is scary. You lose a lot of sleep, you take a lot of notes. I have years worth of files and notes that I've taken out of every poinsettia crop, every variety, the greenhouses that they're grown in."

Horticulturists would recognize the names of the different poinsettia varieties that St. Amant rattles off for a reporter: Prestige, Freedom, Orion, Early Orion, Red Elf, Peter Star, Autumn Red. It takes a discerning eye to tell them apart - to see that the leaves of some are a darker shade of green, or that the petals of others might have a little more orange in them.

"They're so similar, the average person probably wouldn't know the difference," McCarthy said.

The reason for this laborious cultivation of near-identical strains is the necessity of keeping a steady supply of fresh poinsettias in retailer's hands through the brief holiday season.

"Our market goes from the first week of November through the third week of December," says St. Amant. "And within that time frame, you'll grow several varieties to finish."

"The variety you get is most often determined by the week you're buying it," said McCarthy.

None of the plants are marketed under their varietal names.

Altman ships most of their poinsettias locally, though some go as far north as Vallejo; others go as far east as Las Vegas or Arizona.

The best part of the job for St. Amant is seeing the plants ship.

"Hearing the customer's happy, and seeing the plants going out to the stores," she said, "that's very rewarding for me. That means I did my job well, and everyone else then gets to enjoy them, too."