The subject was roses.

"There's not a condescension toward them at all," Prof. Ray Fox of Cornell's horticulture department was saying in the Washington Hilton's flower-bedecked international ballroom.

Around him, perched on white-clothed tables, sat this year's hardly rosy entries in the Syvia Cup competition, an annual competition run by the Society of American Florists. Hundreds of fellow members of the society buzzed about him munching on spare ribs, egg rolls and cucumber rondels with crab meat, enjoying the first reception of their convention week.

"Roses you can't transport that easily," Fox explained, supplying the practical rationale. "Roses in the heat would have opened all up."

Even Walter Preston, a gladiola man from Palmetto, Fla., didn't want to start a war of the roses. "Flowers sell flowers," he smiled, as though not about to speak ill of another colleague's child.

Practical talk occupied a lot of time at the Hilton this week. Unlike the American Institute of Floral Designers convention at the Mayflower last week, the SAF convention draws the whole field of flower people, from growers to wholesalers to retailers. Douglas K. Dillon, the society's president, mentioned how the industry was hoping for legislation that would allow it to organize its advrtising, a la the egg industry, without running afoul of the antitrust laws. Janet Simpson of Carousel Flowers in Jacksonville, Fla., discussed the difficulty of promoting flowers during a recession.

"This is a product you can't cook, can or eat," she said. "When hard times come, this is one of the first things to be eliminated."

Mostly, though, they enjoyed flowers. Especially the Sylvia Cup entries.

This year they aimed at interpreting presidential campaign slogans in flowers. That made for some strange flower-bed-fellows.

"I Like Ike," for instance, an "explosive fanfare to the general" by Joseph Poetker, depended heavily on yellow Fujiyama chrysanthemums. That flower, according to Poetker's wife, legendary floral commentator Frances Jones Poetker, at one time could be owned only by the royal family of Japan.

She turned to this year's blue ribbon winner of the Sylvia Cup, "Two Chickens in Every Pot and a Car in Every Garage," a Herbert Hoover slogan freshly replanted by Louis Pattillo of, Lubbock, Tex.

"A rare sense of humor and subtlety," remarked the only living woman member of the Horticulture Hall of Fame of Pattillo's use of two "hens and chickens" -- the industry argot for echeveria -- as well as a "corkscrew" willow branch and agapanthus, or African lily. "A fine delineation of line with an extraordinary separation of values," she concluded.

She really enjoyed "Turn the Rascals Out," which pressed a white rose into the service of Horace Greeley.

"The white rose signifies purity," she asserted. "He's opposing royal strength and inherited privilege in the chrysanthemums with the purity of the rose. Perfect."

Mrs. Poetker and hundreds of other society members caped their week in Washington yesterday with a White House reception followed by a ceremony conspicuously not in the Rose Garden -- this crowd needed the South Lawn.

The full-time White House press, eager for any opportunity to get close and expecting an appearance by the "Big Pistil," slogged out to cover.

"I've never seen those ropes so high," cracked UPI correspondent Helen Thomas. No one thought it was because the White House didn't want the press diggling into the florists' business.

Rosalynn Carter came out shortly on the arm of a towering Marine guard. Beaming still from the Senate's passing of the Mental Health Systems Act, she thanked them for helping make her house beautiful and bemoaned how her green thumb has suffered since the Carters came to Washington.

"My yards were beautiful," she said of her Plains gardens. "You couldn't tell it now, but they were beautiful."

After being inducted as an honorary member of the American Academy of Florists, Mrs. Carter asked the group to "wander around" a bit before "something else" happened at 3.

The press regulars, moseying around behind the photographers' platform, studiously ignoring the ceremony, knew what was up. They were waiting to throw Billy-questions.

"How many nonelection years can you remember the president meeting the florists?" CBS newsman Robert Pierpont asked aloud to his colleagues. tA few snickers could be heard. Before long, the president walked out of the Oval Office toward the stage.

"Did you talk to the attorney general about Billy on the 17th of June?" called out ABC's Sam Donaldson to Carter's rapidly departing back.

Carter explained to the delighted florists that he had rearranged his priorities, specially a budget session, to say hello. He offered them one "major thought," an explanation of how criticism of government should not blind us to our "blessings" in this country, and one minor one -- a promise of good business in the form of "funeral wreaths for a disappointed party who is going to lose."