Farm owner Roger Brill told People magazine: "She was asking about the trees which drop their needles and those that don't, and which ones smell nice!
"She said that they normally have the Nordmann Fir inside that doesn't drop the needles."
The duchess helped hold up the trees so the children could look at them properly and impressed the farm owner so much, he joked he'd happily give the royal - who made the visit in her new role as patron of charity Family Action - a job working for him.
He said: "She was fantastic with the youngsters. She was in there moving them around and holding them up.
"I will have to give her a job at the weekend, I think. She was a very good saleswoman!"
Catherine also made eco-friendly reindeer food with the children and admired the Christmas decorations they were making, as well as asking them what they were hoping to find under their trees.
A young girl called Poppy said: "I want a real-life unicorn, a Pegasus one that flies. And a little puppy. And a guitar."
The duchess replied: "A guitar is very cool, and very sociable because then you can also sing."
