Free ticket reservations for the opening program of the 2022 Stern Grove Festival, a June 12 program featuring Bay Area luminaries Tower of Power and Too Short, became available online at 2 p.m. Tuesday, May 31.

Within 11 minutes, according to a festival spokesman, they were gone. Just under 10,000 of them.

The lesson was clear: Anyone who wants to attend concerts in San Francisco’s Sigmund Stern Grove this summer, during the festival’s 85th season, will have to watch the clock and move swiftly.

Attendance is still free, but reservations are required to attend. The festival first introduced its competitive reservation system in 2021 to limit the number of people gathering at the outdoor venue due to COVID concerns. Patrons must reserve tickets on the festival’s website,www.sterngrove.org,starting at 2 p.m. each Tuesday, 12 days before the performance date.

For those who miss the initial reservation window, the festival also announced plans to release a limited number of additional tickets at 2 p.m. the following Friday. The first “Flash Friday” offering, for the opening program, is scheduled for Friday, June 3.

The June 12 concert will mark the first public performances at Stern Grove since last year’s festivalwas brought to an abrupt close by a flood caused by a burst water pipe.

The rest of June is scheduled to see performances by Toro y Moi and Hello Yello (June 19) and Liz Phair, Peaches Christ, Madi Diaz and DJ Ladyryan (June 26). The festival continues through the summer with appearances by Cat Power (July 17), the San Francisco Symphony (July 31) and Taj Mahal (Aug. 7).

Stern Grove Festival:2 p.m. Sundays through Aug. 14. Free with reservation. Sigmund Stern Grove, 19th Avenue and Sloat Boulevard, S.F. 415-252-6252.www.sterngrove.org.