Jackson (40), a hooker, played her first game of rugby in 1990.
"I can't remember who we played in my first game," Jackson said.
"I'm glad I've made the 100 games. It is exciting."
She vividly remembers the rest of the season because it was the first year of premier women's rugby in Dunedin, and Pirates won the final.
"That was the highlight for me. We played on Carisbrook and it was the only time we have won the banner."
Jackson will lead Pirates on to the paddock for the semifinal against Kaikorai today, 21 years after she played her first game. She had a two-year break when living in England and another when giving birth to her two children - Ricky (12) and Tamara (5) - and when she worked on night shift.
"A friend asked me if I wanted to play so I borrowed my brother's rugby boots, liked it and just kept playing."
Women's rugby was different in 1990, she said.
"We played like young schoolboys. We were like bees around a honey pot as we chased the ball. The game is more structured today.
"I enjoy playing more than watching rugby. I like the physical contact. Rugby is a good sport for bigger girls to play."
Jackson has a simple recipe for her rugby longevity.
"I just enjoy the game. I've never wanted to give up. When I've had a break I've always wanted to come back."
She made a big impact early in her career and represented Otago in 1992.
Jackson said she would like to continue "for at least the next two years and perhaps longer, but I'll see how my body takes the hard knocks".
"But I don't like practising when it's freezing cold at night."
Jackson is a versatile sportsman and has a black belt in taekwondo. Her son Ricky also has a junior black belt.
Jackson's 100th game against Kaikorai will be played at Hancock Park this afternoon.
The other women's semifinal is between Alhambra-Union and University.
