A walker stumbled across the phone lying next to the uprooted tree in Settlers Park on Sunday morning before handing it into police the following day.

Further inquiries traced the missing mobile to a 15-year-old Bowral teenager, who later admitted to police he was responsible for the damage along with a 14-year-old boy from Robertson.

Although both boys put the damage down to a bout of horseplay, their fuming parents have not seen it that way and have ordered the pair to foot the $250 bill for a replacement cherry tree.

Police say two cherry trees were damaged during the weekend - one pulled out and the other completely mutilated - but the two boys say they were only responsible for damaging one of the trees.

They have taken the blame for the vandalised tree found near Rose Street but say they know nothing about the other tree which was found dumped in the grounds of Bowral Swimming Pool.

Wingecarribee Shire Council gave support to the planting of 528 giant cherry trees straddling the cycleway from Settlers Park to East Bowral seven years ago, standing as a permanent memorial to every Australian killed in the Vietnam conflict.

More than 300 trees have been planted to date, capturing the imagination, emotion and gratitude of Vietnam veterans worldwide but the trees have been plagued by constant vandalism during that time.

Bowral Vietnam Memorial Walk Trust chairwoman Effie Kerr said she was "very excited" to learn the parents had made the culprits take full responsibility for their actions.

"This is the first time we have ever been compensated for a damaged tree and it is something positive to come out of all this," she said.

"This really is wonderful news and I'm also so proud of our local police for their work in tracing the offenders."

Southern Highlands MP Peta Seaton also applauded the boys' parents for taking the bold stance, which she hoped would send out a strong message to others in the community.

"This is a step in the right direction and it is the right thing to do," Ms Seaton said.

"I applaud the actions of the parents involved and they are to be admired for taking this stand.

"It sends out the right message not only to the young people involved but also to other young people who may now think twice about doing this type of thing."