I have two I planted six or eight years ago and one of them has five burs on it. It is by far the smaller of the two trees. First time for either tree to have burs.
This is a tree I planted, I believe, five years ago. Will have to go back through my YouTube videos to verify. It was a tree I purchased on clearance from Wal-mart.
I had 3 deer come out to my dunstans yesterday afternoon. They were planted in 2014 and are loaded with nuts this year. The deer (all bucks) actually walked from tree to tree looking under each one. Pretty cool for the hard work 7 years ago to pay off.
Some of the first Dunstan and Chinese trees we planted 9 years ago down where we hunt have produced for the first time. Below is a pic of a few of the nuts and one of the burrs that was picked up off the ground from under the biggest tree. These trees have received no supplemental watering. Big difference from the ones near my house where I can water as needed. All of these trees were planted at the same time. The ones near my house have been productive since year five.