Manager Derek McInnes told the club's website: "I'd like to add a few more to the squad over the summer.
"The players have done very well this year. But, like every manager, I want to improve every season."
McInnes wants 25-year-old Anderson to prove himself as a first-team regular with the Scottish Premier League outfit.
Garts has done well for us and he is the right type
St Johnstone manager Derek McInnes
"Ando has been here for a while now and he's made nearly 140 starts without ever getting a long run of games," said the manager.
"Hopefully, he will establish himself now and that's the challenge for him.
"Garts has done well for us and he is the right type.
"He had his problems with bookings early on. But, at the start of any season, referees are under pressure to implement new laws. Normally it settles down."
Source: BBC Sport
Source: BBC Sport