Staying blonde was a hassle for Bonnie Steen, so she decided to develop a comb to apply hair color directly to the roots. It took her almost five years to get the applicator right, then her effort foundered because the former college financial-aid adviser knew nothing about marketing and distribution.

Enter Susan Ladua, Steen's daughter, who had some manufacturing and marketing experience. Mother and adult child decided to become partners to get the color applicator company, which they called Roots Only, up and running.

The pairing paid off. Ladua helped snag a contract with Wal-Mart, starting first at their local California store, then expanding nationwide. Steen, 67, focused on strategy and being the public face for the Roots Only applicator while Ladua, 47, tried to make sure that the product was stocked at stores and displayed in the hair-coloring section.

Their company is one of a growing number of entrepreneurial mothers and daughters who are forming and running businesses together. Roots Only expects to hit in $1 million in revenues this year as the company broadens its sales to beauty-supply stores and other outlets to reach more of the estimated 100 million Americans who dye their hair.

As Mother's Day rolls around Sunday, such family enterprises are becoming more commonplace and more visible, said Nell Merlino, president of Count Me In for Women's Economic Independence, a nonprofit group that supports the growth of female-owned businesses.

"We come across mother-daughter businesses regularly now," says Merlino, whose 10-year-old group holds competitions around the country to locate and bolster the business prospects for promising female-owned businesses.

No one tracks the number of mother-daughter businesses. Even the government's official number of women-owned enterprises only dates back to 2002, with an update from the U.S. Census Bureau scheduled for July. A report last fall by the Center for Women's Business Research estimated there are 8 million women-owned businesses—or slightly more than one-quarter of the nationwide total—and they generate some $3 trillion and millions of jobs for the U.S. economy.

The estimate dovetails with data that more women are the sole providers for their households. A CareerBuilder survey released last week found 36 percent of some 600 women surveyed support their household. Many work in offices, but women are also striking out on their own, often in the health care and personal-services businesses, as well as wholesale and retail supply enterprises such as Roots Only.

"These women are problem solvers," says Merlino, who came up with the Take Our Daughters to Work day. "They see a problem that needs to be addressed or a service that needs to be done, and they come up with a solution."

For Steen, it was finding that coloring her hair was "time consuming and messy. I was missing spots on the back of my head and damaging my hair, so I decided to do something about it."

After lots of experimenting, she and her late husband, Claude, finally came up with a prototype, made of straws from WD-40 cans glued to a plastic bottle, that distributed the hair coloring evenly to the roots. Then they found that the cheapest price to make a marketing prototype would be a hefty $50,000.

Ladua, who was working for a medical-device manufacturer, was able to connect them with a skilled machinist who created a model for less than $10,000, which was a more reasonable startup cost.