2017: two-year-old season Kew Gardens began his racing career by finishing seventh in a
maiden race over seven
furlongs at the
Curragh on 7 August 2017. Sixteen days later, the colt started
4/6 favourite against seven opponents in a similar event over one mile at
Killarney Racecourse. Ridden by his trainer's son
Donnacha O'Brien, he took the lead approaching the last quarter mile and won "easily" by four and a half
lengths. On 9 September Kew Gardens was stepped up in class for the
Group 3 Juvenile Stakes at
Leopardstown Racecourse in which he was ridden by
Seamie Heffernan, and finished second of the ten runners, beaten three lengths by his stablemate Nelson. Two weeks later he contested the Group 2
Beresford Stakes at the
Naas Racecourse in which he led for most of the way before fading in the closing stages and coming home fourth of the five runners behind
Saxon Warrior. For his final run of the season the colt was sent to England for the
Listed Zetland Stakes over ten furlongs at
Newmarket Racecourse on 14 October, and started the 13/8 favourite. Ridden by
Ryan Moore he took the lead soon after the start, drew away from his rivals in the closing stages and won by lengths from Dee Ex Bee. Aidan O'Brien commented "Ryan was very happy and said he was very uncomplicated. He's a very good-natured, genuine, good-moving horse. Ryan said he galloped out very well".
2018: three-year-old season On his three-year-old debut, Kew Gardens returned to Newmarket for the
Feilden Stakes on 17 April for which he started favourite but finished third behind Mildenberger and Fortune's Pearl. On 12 May he was made odds-on favourite for
Betfred Derby Trial Stakes at
Lingfield Park but was beaten lengths into second place by Knight To Behold after failing to recover from a poor start. In the
2018 Epsom Derby Kew Gardens started a 16/1 outsider in a twelve-runner field. He was among the leaders throughout the race and went to the front in the straight but was outpaced in the final furlong and dropped back to finish in ninth place. At
Royal Ascot on 20 June the colt was stepped up in distance for the Group 3 Queen's Vase over fourteen furlongs. With Donnacha O'Brien in the saddle he was restrained towards the rear of the twelve-runner field before making steady progress from half way. He took the lead approaching the final furlong and drew away to win "readily" by lengths and a neck from his stablemates Southern France and Nelson. After the race O'Brien said "I'm delighted with him. I thought he'd stay and he was good. He was a little bit disappointing at Epsom, and Donnacha thought we maybe rode him a bit too forward". Kew Gardens was then sent to France for the Group 1 Grand Prix de Paris over 2400 metres at
Longchamp Racecourse on 14 July and started the 7/5 favourite against five opponents including Neufbosc (
Prix du Lys), Dee Ex Bee and Nelson. Ridden by Moore he was settled towards the rear of the field before taking the lead 300 metres out and kept on well in the closing stages to win by lengths from Neufbosc. O'Brien said "The idea with bringing him back to a mile and a half is that we could have a look at whether the
King George would be suitable. That's probably where he'll go next". The colt bypassed the King George for the
Great Voltigeur Stakes at
York Racecourse in August in which he carried a five-pound weight penalty for his Group 1 success and was beaten into third place behind Old Persian and Cross Counter. The 242nd running of the St Leger over furlongs at
Doncaster Racecourse on 15 September attracted a field of twelve runners with Kew Gardens going of the 3/1 second choice in the betting behind the previously unbeaten
filly Lah Ti Dar. The other runners included Loxley (
Grand Prix de Deauville), Old Persian, Dee Ex Bee, Nelson, Southern France, Maid Up (
March Stakes) and The Pentagon (
Tyros Stakes). Moore tracked the leaders before making a sustained run on the outside in the straight. Kew Gardens went to the front two furlongs out and stayed on strongly to win by lengths from Lah Ti Dar with a gap of lengths back to Southern France in third. After the race Moore said "It was very smooth. He's a very uncomplicated horse and he tries very hard. He's got a great attitude to life and he picked up really well. He's a super horse". In the
2018 Prix de l'Arc de Triomphe on 7 October the colt started the 8/1 fourth choice in the betting in a nineteen-runner field. After being restrained by Moore towards the rear he made steady progress in the straight without ever looking likely to win and finished seventh, four lengths behind the winner
Enable.
2019: four-year-old season Kew Gardens began his third campaign in the
Ormonde Stakes at
Chester Racecourse on 9 May. He was made the 4/5 favourite despite carrying top weight of 133 pounds but was never able to get on terms with the enterprisingly ridden Morando and was beaten eight lengths into second place. On his next race the colt contested the
Coronation Cup at Epsom three weeks later in which he led inside the final furlong before being overtaken and beaten half a length by
Defoe. The colt was then aimed at the
Ascot Gold Cup but sustained a back injury in training which kept him off the track until autumn. Aidan O'Brien commented "we were training him for the Gold Cup and he got an injury and it all went pear shaped so we're just so lucky to get him back. He pulled all the muscles in his back just before Ascot. He barely made it back for the Irish St. Leger and that race just didn't go right. He's an incredible horse... He's a very brave horse, so I'm delighted. I'd say the Gold Cup next year would definitely be the target if he stayed in training next year". ==Stud career==