The 15 grass courts of the All England Lawn Tennis and Croquet Club, Wimbledon, are firm and ready.

The center court is emerald green, sappier and more slipperty than the others after 50 weeks of tender care and no play - "a bit juicy," as the players who know it well say, approaching their form - testing first-round matches with surging adrenalin and just a hint of apprehension.

Around London and the surrounding countryside, the chitchat overheard at tea time turns to tennis.

Virginia Wade's new book, "Courting Triumph," was serialized last week in the Daily Mail. Bjorn Borg is on the cover of this week's "Radio Times." The British Broadcasting Corporation has liberally sprinkled its extensive coverage of the World Cup soccer tournament with tennis previews. A woman's magazine features an interview with handsome Englishman John Lloyd on sex and the single tennis player.

It is time again for the tournament that is officially entitled "The Lawn Tennis Championships," and known throughout the tennis-playing world simply as "Wimbledon."

Having celebrated its centennial last year with appropriately stately ceremony and a spate of memorable matches, the oldest and grandest of tennis championships gets down to accumulating a second century of lore tomorrow.

The prospects on court are as rich and inviting as the fresh strawberries and cream that symbolize the social trappings of this favored summer sporting festival of the British middle class.

Defending champion Borg and Jimmy Connors head the table-laden men's singles field of 128. They are seeded No. 1 and 2, respectively, and favored by London bookmakers to meet in a rematch of last years bruising, thrilling five-set final.

Borg, who was last beaten in the first week of March and has won 33 consecutive matches since then, excluding two defaults because of infected blisters, could become the first man since Rod Laver in 1967 to sweep the Italian, French and Wimbledon titles in one summer.

More important, the 22-year-old Swede is seeking to become the first man since Englishman Fred Perry in 1934-35-36 to momopolize the Wimbledon singles trophy three successive years.

Chris Evert, 23, is seeded No. 1 in the women's singles draw of 96, keen and eager after taking the first three months of the year off, her first "vacation" from tennis since she became a superstar at age 16.

Evert will be severely tested as she tries to recapture the title she won in 1974 and 1976. The women's entry is the strongest in several years, with Martina Navratilova, Evonne Goolagong Cawley, defending champion Virginia Wade and Bille Jean King expected to pose the toughest challenges.

Navratilova, 21, the powerful expatriate Czech left-hander who now lives in Dallas, dominated the women's pro tour in Dallas,absence last winter, winning seven consecutive tournaments and 37 match between January and March. Her triumph over Goolagong in the final of the Virginia Slims championships at Oakland in April was the most important victory of her career and did wonders for her self-esteem.

Navratilova has an aggressive serve and volley game well suited to grass, has matured tremendously in the past year, and is in superb form. She routed King in the semifinals of the Colgate International at Eastbourne on Friday, and yesterday saved a match point in beating Evert, 6-4, 4-6, 9-7, in the final period.

This, too, was a great confidence booster; she had not played Evert this year and had lost their last five meetings in 1977.

Goolagong, 26, the only one of the leading women contenders who has not been playing World Team Tennis in the United States this summer, is in good form despite the persistence of foot problems that plagued her throughout the winter.

The lithe and graceful Australian, winner here in 1971 and runner-up in 1972-75-76, missed last year's tournament following the birth of her first child, daughter Kelly. Goolagong rested her tender feet last week after winning two tuneup tournaments on English grass without losing a set, though against relatively minor opposition.

Wade, 32, "Our Ginny" in the British popular press, sent England into giddy ecstasy with her sentimental triumph last year, winning for the first time on her 16th attempt, is the year of the centenary and the Queen's silver jubilee.

Her victories over Evert in the semifinals and Dutchwoman Betty Stove in the final provided the fulfillment of a lifetime. Wade has done little of note this season, failing to go beyond the semis in nine Slims tournaments, but sounds determined to defend her crown.

King, 34, lost three times in a row this year to her former "pigeon," Navratilova, and has won only 19 games in six consecutive losses to Evert the past two years, but she is the dominant Wimbledon player of the postwar era, and the Center Court is her most beloved stage, capable of inspiring her to unforgettable performances.

King also still is seeking the all-time career record for Wimbledon titles in singles, doubles, and mixed doubles. In 1975 she tied the record also held by Elizabeth Ryan, now 86, who won 12 women's doubles and seven mixed titles between 1914 and 1934.

King, winner of the singles six times between 1966 and 1975, is likely to seize title No. 20 this year - if not in sigles, then in doubles with Navratilova or in the mixed with Australian left-hander Ray Ruffels.

At Wimbledon, almost uniquely in the high finance world of pro tennis today, titles are valued much more dearly than the $400,000-plus prize money.

The tournament's heritage, its air of understated elegance and superiority, and its sublime setting make it so.

"I think of the Center Court at Wimbledon as a religious person might think of a cathedral," John Newcombe, the champion of 1967-70 71 and the No. 16 seed this year, has said. "When you are out there, it's what this game is all about. An awful lot of history has occurred on that court.You can almost feel all the game's past greats looking down at you, judging what you're made of."

Regal visitors frequent the royal box, watching the current kings and queens of tennis and the pretenders to the throne struggle on the Center Court, the most famous plot of tennis turf in the world.

Every player with a realistic chance to win is keyed up, striving to hit peak form at the right time. "I'm more nervous than I have been in a couple of years, and that's good," Evert said last week. "You want to be nervous, excited, emotional when you play here, because that brings out the fine edge in your game."

Tomorrow at "2 p.m., precisely" - the customary starting time each afternoon at Wimbledon, where tradition and clockwork efficiency are revered - Borg will open the center court program against Victor Amaya, the left-hander from Holland, Mich.

"I don't see why Borg can't win his third title in a row," said Perry, who insisted it would be "a good thing for the game" if his 41-year-old achievement is equalled.

"A fellow doesn't give up the Wimbledon title without one heck of a fight, and Borg is a fighter. He has great concentration and pride of performance.

"I think the only man he has to worry about is Connors, and Jimmy apparently is smarting pretty much (he has lost three of his last four meetings with Borg.) He wants to clobber him at Wimbledon more than anywhere else, and he's got his best chance to do it on fast grass."

Connors, 25, rested last week after winning back-to-back English grass court tournaments at Beckenham and Birmingham, his first competition since a bout with mononucleosis.

Borg has had 10 days of intensive grass court preparation after leading Sweden to a 3-2 Davis Cup victory over Yugoslavia on clay in Belgrade the week after his triumph in Paris.

If form were to hold true to the seedings, the men's pairings in the round of 16 on Saturday would shape up like this: Borg (No. 1) vs. Buster Mottram (12); Sandy Mayer (8) vs. Wojtek Fibak (13); Guillermo Vilas (4) vs. 1975 champion Arthur Ashe (15); Roscoe Tanner (6) vs. Ilie Nastase (9); Brian Gottfried (5) vs. John McEnroe (11); Vitas Gerulaitis (3) vs. Dick Stockton (10); Raul Ramirez (7) vs. Newcombe (16), and Connors (2) vs. John Alexanders (14).

The women's draw at the same stage would find Evert (1) vs. Kerry Reid (10); King (5) vs. Sue Barker (14); Wade (4) vs. Marita Redondo (16); Wendy Turnbull (7) vs. Mima Jausovec (12); Stove (6) vs. French Open champ Virginis Ruzici (13); Goolagong (3) vs. Regina Marsikova (15); Dianne Fromholtz (8) vs. Marise Kruger (11), and Navratilova (2) vs. 15-year-old phenom Tracy Austin.

Anticipation of all the wild possibilities that could be played out against the sumptuous backdrop of the All England Club, where history clings to the dignified green walls like the vines rustling in the breeze, and tennis and customs are both observed with sober respect, make the Wimbledon fortnigth irresistable.

England, as every year at this time, has acute tennis fever.

It is Wimbledon time again.