Civil Aviation Safety Authority staff enjoy free office greenery while members of parliament have to resort to "self-funded" pot-plants, a senate committee has heard.

The authority spends about $50,000 a year on plants but officials couldn't tell Nationals senator Fiona Nash how many it had.

It has just issued a three-year tender for maintenance and replacement of the office greenery.

"What's wrong with the plants you've got now?" Senator Nash asked during the senate estimates hearing on Tuesday.

"I think a lot of that's to do with the turnover and natural attrition of the plants," director of aviation safety John McCormick replied.

Senator Nash observed maybe someone hadn't been watering the plants, to which Mr McCormick said CASA staff weren't allowed to.

The senator told the hearing the Department of Parliamentary Services had taken away plants from parliamentary offices during a round of cost-cutting.

She had a "self-funded plant" named Pete.

"I'm intrigued to know why CASA has plants and members and senators don't," Senator Nash said, "'cause Pete's a bit lonely, I can only afford one."

"That is terribly unfair, Senator," Mr McCormick replied.

He said CASA would be considering the matter of the plants in its cost cutting review.

"I'm agnostic about plants," he said.

"That doesn't surprise me, Mr McCormick," Senator Nash replied.