Boy, 7, in serious condition after struck by tree branch at butterfly farm

A boy, 7, is in a serious condition in hospital after he was struck by a tree branch on a butterfly farm on the banks of the Hawkesbury River, police said.

The boy was flown in a helicopter from the Butterfly Farm and Ski Garden at Wilberforce on Saturday morning.

Paramedics arrived at the Wilberforce Road property to find the boy with a serious head injury.

He was treated at the scene before being airlifted to Westmead Children's Hospital.

Police said the boy remained in a serious condition at midday.