Mary Louise Parker stars as a marijuana-dealing suburban widow in Weeds.

It's funny to recall how controversial Weeds was in its 2005 debut.

Times can change right before our eyes and we don't even notice.

The thought of a marijuana-dealing suburban widow -- played by Mary-Louise Parker -- with two kids outraged moral-watchdog groups. At the very least, even if you weren't among the appalled, most people considered the subject matter to be cutting edge, so to speak.

Could a highly-stylized storyline like this sustain itself for very long?

Well, the fourth-season finale of Weeds will air tonight on Showcase. Obviously, to have stuck around for this long and to continue to be so critically acclaimed, Weeds is doing a lot of things right.

"I'm always surprised, truthfully," said Parker, referring to her string of award nominations for her portrayal of Nancy Botwin. "I don't take it for granted. Maybe it's just lack of self-esteem or something."

Parker, of course, has no reason to be lacking in confidence.

It took us a little while to get into Weeds. We always were intrigued by it, but early on some of the characters were too extreme to be likeable in an enduring way.

In the past two seasons, Weeds has become one of our favourite shows. It has found the right tone and right balance between life-threateningly serious and side-splittingly funny.

The characters -- Parker, Elizabeth Perkins as Celia, Justin Kirk as Andy and Kevin Nealon as Doug -- drive the narrative with flair.

And in a grand stroke of luck for creator Jenji Kohan, the kids in the cast -- Hunter Parrish and Alexander Gould as Nancy's sons Silas and Shane, as well as Allie Grant as Celia's daughter Isabelle -- have blossomed into great actors, too.

"I don't get to work with Elizabeth that much, but pretty much everything she does, I'm kind of enthralled by," Parker said. "Especially in terms of comedy, she's extraordinary.

"Justin, the same thing and Hunter, too . . . he's just getting better every day.

"We've got an amazing cast."

The fourth season of Weeds has seen Nancy and her family flee from their fire-ravaged California suburb to the coastal town of Ren Mar, perched beside the Mexican border. Nancy winds up fronting a retail clothing store for her old drug associate Guillermo, played by Guillermo Diaz, and in the back of the store there just happens to be a tunnel stemming from Mexico.

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IF YOU WATCH

What: Weeds season finale

When/Where: Tonight, 10 p.m., Showcase