Biting back a mischievous grin, Connie Sue Patterson leans forward and puts on her best conspiratorial face.

“I tell you, I have THE secret to combat aging,” the 53-year-old Prairie Patches employee says, pausing for dramatic effect.

A few steps away, fellow employee Alice Leitch, 65, arches an eyebrow, but plays along. An encouraged Patterson takes the bait.

“The secret,” she says, “is that I refuse to grow up — really, that’s all it takes.”

Leitch laughs, but quickly nods in agreement — she’s in on the secret, too. Red Hat Society sisters, after all, stick together and think alike. You could call it something of a rebellious, middle-aged coup.

The Red Hat Society, now an international phenomenon, began four years ago in California. Founder Sue Ellen Cooper wanted to put together an organization for women age 50 and older. Her goal was to create a network of female friends who were at a similar point in life.

“I think that’s actually a nice way of saying we’re all getting old,” Patterson says.

The politically correct approach, however, seems to be working. Since its inception, the Red Hat Society has infiltrated 20 countries and now includes 20,000 chapters and a U.S. membership of 400,000. Red Hatters in Lawrence reflect a similar growth pattern. In early 2003, the city had only two society chapters; as of this week, it has eight.

“The whole Red Hat idea has just spread like wildfire,” says Cinda Garrison, owner of Prairie Patches, 821 Mass. “It’s really quite something.” Garrison herself is a new addition to the Red Hat bandwagon; she launched her own chapter last month.

“We’re just getting started,” Garrison, 62, says, “but we’ve already got some good ideas.”

One such idea, in fact, has already materialized into a Red Hat event. On Saturday, the Prairie Patches store will be transformed into a “Red Hatters May Day Celebration” for society veterans and newcomers alike.

“We’re going to have a bunch of fun activities and give ladies in the area a chance to see what the Red Hat Society is all about,” Garrison says.

You may be wondering how the Red Hat Society got its name, and the answer lies in a 40-year-old British poem. Founding crimson-top Cooper was inspired by writer Jenny Joseph’s “Warning,” which begins with this line: “When I am an old woman I shall wear purple / With a red hat which doesn’t go and doesn’t suit me.”

The group’s guidelines, Garrison says, are as simple as that.

“We don’t have many rules — just that women over 50 wear red hats and purple clothes when we meet,” Garrison says. “Younger women are welcome, but they must wear pink and lavender until they meet the age requirements. We think it gives them something to look forward to.”

Lori Lange, 46, says she’s been stocking up on pastels since joining the Prairie Patches group.

“I’ve got four more years to go, so I’ll be in pink for awhile still,” she says, laughing.

Across town, Bobbie-Frances McDonald, 59, has a couple of nonwardrobe related rules for her own newly-formed Red Hat Society chapter, “The Pink Ladies and Red Hot Mammas.”

“I just tell women to come with a big smile and open arms because we are all about having fun,” McDonald says. “And along those same lines, I have two more rules: no gossiping or discussing ailing body parts.”

Garrison says McDonald’s rules drive home a point that every good Red Hatter should remember.

“Age is nothing but a number,” she says. “Live young and be with friends — that’s what Red Hat is all about.”