The garden was the U-Turn Trust's flagship project, born out of the 2008 "enough is enough" hikoi organised by Mr O'Keefe after a spate of violence in Flaxmere, including a home invasion in which his daughter was threatened and her partner badly beaten.
"Our people said they needed a garden where they could come together, feed each other, nurture the garden and each other."
Mr O'Keefe said volunteers had already sprung into action yesterday to ensure the garden's vegetables were watered.
They were salvaging parts of the hose and transporting water to the plants with buckets.
The garden would remain open to the public despite the attack, which Mr O'Keefe had not reported to police.
He said volunteers at the Community Garden had a duty to keep it functioning.