Actress Joan Van Ark Unties the Knot : Television: One of the original cast members of ‘Knots Landing’ is leaving to pursue other interests.

It’s official: After several weeks of published speculation about her future as Valene Ewing on “Knots Landing,” Joan Van Ark has confirmed that she is departing the popular CBS prime-time serial.

Having originated the character on predecessor “Dallas” in 1978, the actress has played the role for 13 seasons on “Knots,” opposite Ted Shackelford as her on-again, off-again (currently on-again) husband, Gary Ewing. Shackelford and Michele Lee (as Karen MacKenzie) thus become the series’ only two remaining original cast members.

“I could stay forever on the show and be safe,” Van Ark said Wednesday, explaining her decision to move out of the “Knots” cul-de-sac.

“But three years ago I did ‘Night of the Iguana’ in Williamstown (Mass.), and I had a quote from Tennessee Williams taped on my mirror, taken from an essay he’d written on success. It said, and I’m paraphrasing here: ‘Security is in the shape of a kidney-shaped pool in Los Angeles, where you sit waiting for your residual checks.’ I was in a comfortable spot on ‘Knots,’ and an artist should not be comfortable.”

Van Ark had announced plans to leave two years ago, but changed her mind after being promised an opportunity to direct and other professional perks.

“This year was the last of those two years, and all through this year, I’d decided this would be it--without fanfare, because I had done a lot of interviews before and then I hadn’t left, and it would seem like crying ‘wolf,’ ” she said.

During the period from Thanksgiving to New Year’s when the show shut down to revamp, her agents told creator-executive producer David Jacobs and executive producer Michael Filerman that she wanted to leave.

The day after “Knots” wrapped production for the season in April, Van Ark tested for an NBC half-hour sitcom, “Spin Doctors,” was told two days later that she had the part, and began rehearsing, filming a 20-minute presentation rather than a pilot.

Much to her surprise, the show was not picked up. “It had felt like a gift from heaven,” she said. “And here I sit before you, an actress who made a decision to move forward without the gift I thought I had. To say I wasn’t devastated isn’t true. I was. The (new show) would have solved a lot of things. But if I’d had it to do over, I would have done everything exactly the same.”

In making her final decision to leave, Van Ark drew inspiration from her husband, veteran news reporter John Marshall, who in January was abruptly terminated by KNBC-TV Channel 4 after two decades with the station. He then accepted a job offer from KCOP-TV Channel 13, but resigned after one day to pursue other interests.

“He did make me think twice, because someone in the family . . . my responsibility was greater now to maintain a continuum,” she acknowledged. “But he inspired me--he was offered many things, chose one and realized that this was the same thing, it wasn’t right. So he called a halt gracefully.”

Not that Van Ark is departing on bad terms. “I have loved more than life the 13 years I’ve had on that show,” she said. “David Jacobs is a great influence on my life, has taught me so much about so many things. Ted is the other half of every breath I take on the show, and personally, he’s a large part of my heart. The people are my family--we have shared marriages, deaths, divorces. It’s far more difficult to leave than I thought.”

Van Ark does not yet know what Valene’s fate will be; on the season-ending cliffhanger, the character was off to Florida to follow up a lead for a book she was writing. Jacobs, who was unavailable for comment, has told her that the first four weeks of the new season will include a “Where’s Val?” storyline.

The actress admits that it was only this last Saturday, when the cast gathered for a memorial to Larry Riley (who played Frank Williams until his death from AIDS-related renal failure), that she began to consider the ramifications her leaving would have for her character.

“I’d forgotten that there was a character I’d loved for 13 years. She was the seed of the show. I am the sole person to spin off from ‘Dallas’ (because actor David Ackroyd originated the role of Gary on that show). Valene gave ‘Knots’ a note of spirituality. There was a heart that was Valene. I hope they treat her with respect, that she is seen out with a resolution she deserves.”

That does not mean, though, that Van Ark will participate in the send-off. “I have to be honest with you. I don’t know,” she said.

She will return to the set to direct, and also show up next season in a CBS film, “The Grand Central Murders,” opposite Richard Crenna. In the more immediate future, she starts rehearsals next week for the Grove Shakespeare Festival production of “Macbeth,” playing Lady Macbeth.

“I don’t want (the roles of) Lady M and Blanche Dubois to get by me. I want to be the Joan Van Ark I was before ‘Knots Landing,’ doing a lot of different things. I hope the ‘Knots’ viewers will say, ‘You broke our hearts’--and then I hope they follow me on my journey.”

Van Ark does credit the series with providing her some challenging work, especially during the 1984-85 season when, having suffered a nervous breakdown after being told her twins were stillborn, Valene assumed the identity of a woman named Verna Ellers. In one episode, Van Ark said, she painted her face like a hooker and tried to pick up a man in a bar. The morning after, in a five-minute continuous scene that the actress says is her best “Knots” work, a remorseful Verna scrubbed off the makeup, put on a soft new face and blotted her lips.

“And you know something?” Van Ark said. “I didn’t think of it till now, but that’s what I’ve done with my life.” She smacks her lips in the same blotting motion.

“I’m ready.”