Diane Haithman is contributing to Deadline’s coverage of TCA.

According to executive producer Kevin Williamson, there won’t be any guest crossover, or story crossover, between the CW’s The Vampire Diaries and the network’s new series The Secret Circle, making its debut Sept. 15. Even though both series are based on supernatural book series by the same teen-appeal author, L.J. Smith, Williamson told a TCA audience today that an effort is being made to keep the shows separate. The witch mythology of Secret Circle and the vampire-werewolf-occasional witch mythology of Vampire Diaries, he said, just don’t mix. “I don’t think you’ll see that crossover,” he said. “That would kind of limit us. We want to create our own story.”

And it’s not just about the mythology. Secret Circle is shot in and around Vancouver, B.C. and Williamson was asked whether it might not have been easier, financially and physically, to shoot the new show on location in or near Atlanta, where Vampire Diaries is shot, Williamson said: “I don’t want the show to look like Vampire Diaries.” (He acknowledged after the session that Vancouver “priced out” over some other locations. “It made sense financially, visually.”

Williamson — co-executive producing Secret Circles with Andrew Miller (Imaginary Bitches), Leslie Morgenstein (The Vampire Diaries, Gossip Girl) and Gina Girolamo — said following the panel that taking on a new show will not affect his involvement in Vampire Diaries as co-showrunner with longtime collaborator Julie Plec. “We call each other every night and cry for two hours and figure out what we’re going to do. We’re joined at the hip.” He said he has tried to talk Plec into assuming creative duties for the new show but so far she has resisted.

Williamson — who appeared on the panel with co-execs Girolamo and Miller, as well as star Britt Robertson and other cast members — also said that the world of magic lends itself to a slightly lighter tone than the vampire scene. “It’s an honest reaction to the world around them, they are suddenly making this magic. There is a certain snark to that,” he said. But not too light, a la Sabrina the Teenage Witch: “It’s very dark, but not that hard-edge ripping hearts out and slicing people open like Vampire Diaries,” he said. “We’re just challenged as to what can witches do? Yes, there will be humor and scary witchy-woo.”

As have other CW panelists today, Williamson challenged the notion that either show is intended to be just for that network’s coveted 18-34 demographic, which is to say that not everything happens in high school corridors. “The vampires are 164 years old,” he points out. “And what I love (about The Secret Circle) is that it is multigenerational, it’s not just a teen show. It’s a very adult show, and it’s going to get very adult, very fast. We’re going more in that direction.”