In 1989 she joined a lawsuit protesting Moi's proposal to build Africa's highest skyscraper with a statue of himself in Uhuru Park, a rare green space in Nairobi. A government official derided her "clique of women" as a "bunch of divorcees."
In 1992 she spoke out against Moi when he dragged his feet on introducing multiparty democracy, and she was arrested for allegedly spreading rumors of a coup.
She remembers those times when she was so politically radioactive that people would cross the street when they saw her coming.
"It does make you feel lonely," she recalls. Then she chuckles. "If people are avoiding you on the streets, you know they aren't going to invite you for dinner."
Maathai was arrested over and over, though the stings were brief. Over breakfast, she speaks of her experiences in jail.
"It is dehumanizing. It is filthy. It is crowded. You are put in areas where people will mock you -- guards and even prisoners. You are put there to humiliate you. I remember one time I was put in a place that was so crowded with drunken people."
She stops in mid-sentence, then says, "Let's talk about jail after we eat." She cringes. "The images spoil my appetite."
In 1992 she also led a sit-in and hunger strike for several days with mothers whose sons were held as political prisoners.
"The mothers of these young men in jail came to me because they knew that I had become known as a person who is not afraid, a person who is willing to stand up and ask questions and articulate issues for the rights of others," she says. "So the women came and said, 'Can you help us?' "
Their protest attracted thousands of people, and police in full force. In a technique that became infamous, some of the mothers stripped in front of the soldiers to show their disgust. It is an old tradition, says Maathai, in which a curse is believed to fall on a young man who views the nakedness of a woman old enough to be his mother.
Maathai did not strip. But she was beaten unconscious by police swinging clubs and woke up in the hospital just a few months before she was to visit members of the U.S. Congress and then attend the Earth Summit in Rio de Janeiro.
Her international prominence, she says, helped keep her prison stays short.
"The weakness of the Moi government was that it was very oppressive at home, but it was trying to create a very good image abroad," she says. After one of her arrests, Al Gore came to her defense, making calls to secure her release.
"I was empowering people with information. It was not the tree planting that Moi was against; he was against the educational component, the civic and environmental education, because that touched on governance, touched on democracy, respect for human rights, respect for environmental rights, protection of natural resources, equitable distribution of resources."