Gardener, who starts for the Centro Sportivo Carabinieri, made his first international appearance at the 2009 Junior World Championships . There he finished 29th in the sprint, 20th in the skiathlon and fourth in the relay. In the following year he came at the Junior World Championships in Hinterzarten on the 23rd place in the skiathlon, on the 13th place over 10 km classic and on the seventh place with the relay. In February 2010, he ran in Forni di Sopra for the first time in the Alpine Cup and achieved 37th place in the sprint and 27th place over 10 km classic. In the 2011/12 season he made it into the top ten twice in the Alpine Cup and thus reached 16th place in the overall standings. At the U23 World Championships in Erzurum in 2012 , he achieved 29th place over 15 km classic and 17th place in skiathlon. He made his debut in the World Cup in February 2014 in Toblach , which he finished classically in 70th place over 15 km. In the 2014/15 season he achieved over 15 km freestyle in Oberwiesenthal and in Rogla in the 30 km mass start race with third place each his first podium places in the Alpine Cup and at the end of the season 20th place in the overall standings. In February 2018 he won the Gsieser-Tal-Lauf over 42 km freestyle. At the final stage of the Tour de Ski 2018/19 , which he finished in 34th place, he got his first World Cup points with 29th place.
In the 2019/20 season, Gardener achieved six top ten placings, including second place over 15 km classic in Campra and first place over 15 km freestyle in Piancavallo , third place in the overall ranking of the Alpine Cup.
Italy