A seed planted early on in “Gotham’s” run is about to come into full flower – and her name is Poison Ivy.

Set in the era between the murder of Thomas and Martha Wayne and the emergence of their son Bruce as the costumed vigilante Batman, when the FOX series returns for a third season Sept. 19, one of the latest proto-villains taking center stage will be an early incarnation of the Dark Knight’s plant-obsessed, man-manipulating seductress.

The character, renamed Ivy Pepper for the series (a departure from her familiar comics alter ego Pamela Isley) and played by 14-year-old actress Clare Foley, first appeared in the very first episode. The young girl's mobster father was subsequently gunned by police and her abused mother committed suicide, but Ivy, often with her friend Selina Kyle at her side, has been able to sustain herself among the fringe elements of the city.

For Season Three, Ivy’s doing some growing up, both figuratively and literally. 28-year-old actress Maggie Geha assumes the role when Ivy’s hormones assert themselves dramatically, a jaw-dropping transformation that sets the stage for her eventual evolution into a femme fatale in line with, but not exactly the same as the character’s comic book profile.

“Our take on Ivy is definitely going to be different than the Ivy of the books,” says the series’ executive producer John Stevens. “Our Ivy is mentally and emotionally still like a 14-15-year-old girl, but she’s in the body of a 25-year-old woman, so she is not quite the femme fatale that she will later become in the comics... It will be a story of somebody who’s actually discovering the power that they now have as they grow up and say, ‘Oh wait – now I actually have this ability to pull people in, pull in men, and learning how to use that – and abuse that.”

Ahead of her “Gotham” debut, Geha joined CBR to offer her take on the series' new, but maybe not exactly improved, Ivy.

CBR: Once you got your sense of who Poison Ivy was, who she’s becoming. what was most exciting to you about her?

Maggie Geha: I love that she is multi-dimensional. She’s got this side of her that’s very nurturing and loves plants, and she’s vegan and she loves animals, and that’s very much like myself in my personal life. I mean, I can totally relate to that, and I love that. I love that part of her. I’m thrilled that she has that part of her.

On the other hand, she’s undergone this transformation, and she’s kind of finding out who she is, so I’m also finding out who she is. She’s in a new body, so she’s figuring out what that means, and how that changes her life, and her interactions with people.

She’s got a very dark side to her -- a very dark, and sinister side to her that’s very manipulative. That part is going to be so fun to play, because I’m not dark at all. Let’s be real: I’m about as light and bubbly as you can get! I love being able to play that side of her.

How about the vampy side, because, obviously, sexuality has always been a big part of the character. You’re at the beginning of it: what was that like, to figure out how you were going to come at that?

I think that everything with the sexuality part of it – it’s less about Ivy feeling sexual, and it’s more about her manipulating people. If somebody finds her appealing in a sexual way, that’s a flag to her, “Okay, I need to change the way that I behave now, so that I can utilize this person and get what I need from this person. What can this person do for me?” If that means utilizing her sexuality, then so be it. I think she’s pretty reckless. I think she’s a wild child.

How will she mess things up with the people who know her, like Selina Kyle and like Bruce Wayne.

Ivy’s just been so secluded from society -- as we saw in Clare Foley’s performance in Seasons One and Two, she really only had Selina as a friend. Her parents are gone, no other friends. She’s in and out of foster homes. I think maybe she spends a lot of alone time with her plants, because that’s where she feels comfortable and at home. I think she’s trying to figure how to, basically, be a functioning human in society, and that’s maybe not the easiest thing for her.

How comfortable is the wardrobe for you? Did you find your way into the character with the clothing, in a way?

Well, Ivy wears a lot of green, naturally, and I love that. As a redhead, I love wearing green because it signifies, like, toxicity, and poison, envy, jealousy, but it also signifies nature, and growth, and youth, and a lot of good things, too. It’s a great color for her. Yeah, I’m thrilled to be wearing green.

In researching and looking at the different versions of Ivy that have existed in the movies, in the comics, the animated show and now “Gotham,” what was the fun discovery, exploring of all those iterations of Poison Ivy?

It’s invaluable to have Clare Foley's performance in Seasons One and Two, to be able to see, essentially, my very own character, just in a younger form. [That's] so special. That’s really, really special that I have that. Nobody else really has that. I feel very lucky and grateful to have that.

I’ve read Ivy’s first miniseries from DC Comics, and that was awesome. I love the comics. I actually dressed up as Ivy for Halloween a few years ago – love the comics! And, of course, Uma Thurman -- I think she’s the only film appearance of Ivy that we’ve ever seen. I thought that movie was really fun, and of course, her performance was amazing. What else? The animated cartoons of Ivy are really fun to watch. I watch a lot of clips of that on YouTube.

I haven’t actually gotten into the superhero with supernatural powers area yet. That we haven’t delved into. It’s definitely still staying true to the show and the origin stories of the character, so it’s more about Ivy’s development early on as a young woman. We haven’t gotten into the crazy supernatural area yet, but I hope the show goes on and on and on and on and on and we get there. I think that’d be so fun.

What little thing did you do in your audition to try to put it over the top? Did you have a little angle that you were trying to work?

You know, I taped for it, because I used to live in L.A. – I just moved to New York, so I taped from L.A. for the New York casting office. In the “sides” they gave me, there was a very sharp turn in her motives. It was very bipolar. She went from one extreme to the other very quickly, changing on a dime.

That’s kind of what I played up in my audition, how quickly she can go from -- how unpredictable she is, and you kind of never really know if she’s being genuine or not. I think she’s a little bit of an actress.