The Dunedin cyclist was in blistering form to start the New Zealand criterium championships at the weekend.
He pulled away from the pack 10 minutes into the race to lead from the front.
The defending champion put his pedal to the metal, leading solo for at least 40 minutes and later lapping the field in Invercargill.
Eventually, he was caught by a small group dominated by his New Zealand Cycling Project Mito-Q team-mates, and Ben Oliver, who won silver at the Commonwealth Games, sneaked ahead.
Oliver crossed the finish line first to win the men's elite national title, while Gardner was runner-up and won the under-23 title.
While there was "a bit of pressure" for Gardner being the defending champion, he was thrilled with his, and the team's, results.
"It was really cool, actually," Gardner said.
"We had a strong team of us eight riders. We had a pretty clear team goal of what we wanted to do.
"We adapted well to how the race went, and the plan wasn't for me to go solo off the front by myself and lap the field, it was far from it, but it worked out really well in the end.
"We were super happy to not only get the elite jersey, but for me to get the under-23 jersey as well."
The 19-year-old is preparing for another big season at home and abroad.
He will compete in the time trial and the road race at the elite road national championships in Timaru on February 6-8, and switch disciplines to ride at the national track championships at the Invercargill Velodrome from February 24 to March 1.
After that, his focus will shift towards his second stint in the United States and Canada with his team.
Gardner, who leaves in early May, will embark on a similar circuit to last season through Washington DC, New York, Chicago and Canada.
"It's cool to sort of get an atmosphere of the place as well, because we stay in quite a few host houses.
"We get to stay with a bunch of families and get a real [sense] of what it's actually like."
Gardner looked forward to heading back on the circuit for a second year and felt like he made great strides towards the end of last season.
"We had a big breakthrough near the end of the season.
"Just understanding the racing and being more confident in terms of our abilities, and where our strengths and weaknesses, you could say, lie, and how we utilise those to be on the podium ...
"By the end of that campaign, and throughout the middle, we had a few really good results that we were happy with.
"It'll be great to hopefully start off at a similar position to what we left last year and then just continue to build and know what we're in for, I guess."