(RNS) For many church leaders, Christmas and Easter are prime opportunities to woo people they affectionately call  “poinsettias” and “lilies” to more active membership.

So they pull out all the stops, hoping those twice yearlies — named after the seasonal flora decorating sanctuaries and homes at Christmas and Easter — might catch the message.

[ad number=“1”]

Willow Creek Community Church, a megachurch with locations across the Chicago area, gets a healthy bump in numbers each year among people also known as “Chreasters.”

Willow Creek Community Church in South Barrington, Ill., boasts one of the largest congregations in America. More than 15,000 worshippers a week attend the church. Photo courtesy of Willow Creek Community Church

This year, the church with multiple locations is holding eight Christmas services at its main campus, and a special family-oriented service led by the families of two pastors on Christmas Day.

In 2015, Willow Creek hosted almost 60,000 people at its main campus for Christmas services. That’s compared to the usual 15,000 to 17,000 on a regular Sunday.

[ad number=“2”]

Despite the larger captive audience at Christmas, Willow Creek teaching pastor Steve Carter said the church doesn’t doesn’t spend a lot of time advertising to newcomers. Its message to the congregation about normal hours and benefits of membership is compressed into two minutes.

Instead, Willow Cheek lets the service speak for itself.

“We think if you do something and have something to say, they’re going to be curious,” Carter said.

Graphic courtesy of LifeWay Research

Planning for the large-scale Christmas production begins about six months in advance, with an estimated 20 people participating.

Carter called the number of people who convert to Christianity after their Christmas services “amazing.”

Blaine Hogan was one of those people.

In 2001, his then-girlfriend, a longtime Willow Creek member, took him to one of the church’s Christmas rehearsals, where he was stunned by the drama. The creative team had used projection technology to display stars on the ceiling in an impressive technological presentation.

“I remember standing in the auditorium being blown away,” Hogan said. “I saw the possibility of art and faith at it was being displayed in these Christmas services.”

At the time, Hogan was Catholic and had previously been attending Mass about once a month. That service eventually drew him back to Willow Creek, where he now serves as one of its creative directors.

[ad number=“3”]

Carter and Hogan said the Christmas season is the perfect time to reach out to the so-called poinsettias and lilies that show up every year.

“Our hearts are softened during the holiday season,” Hogan said. “There’s this cultural window of time where we’re more reflective and hopeful. People are searching for truth.”

Graphic courtesy of LifeWay Research

Last year, LifeWay Research found that of the 1,000 Americans they surveyed, most (57 percent) would be likely to attend church at Christmastime if someone they knew invited them to go.

“Regular churchgoers may assume the rest of America has already made up their mind not to attend church,” said Scott McConnell, executive director of LifeWay Research. “In reality, many would welcome going to a Christmas service with someone they know.”

“It’s an easy invite,” added Carter. “They see what the church has to offer.”