Gardiner was introduced to mountaineering, in
Snowdonia, by his father at the age of eleven, his first alpine ascent was made in 1869 when he ascended
Monte Rosa. The following year, with
Lucy Walker and her father, he climbed the
Matterhorn, the first ascent by a woman and only five years after
Whymper had first ascended the mountain. He made the first ascent of
Mount Elbrus with
F. Crauford Grove,
Horace Walker and the guide of
St. Niklaus in 1874 and it was also in 1874 that he first joined forces with
Charles and Lawrence Pilkington, the cousins of his future wife. He regularly hired Peter Knubel as his guide, Knubel was with him on Elbrus and they had made the first ascents of
Les Rouies and the
Roche Faurio together before that. Knubel was also with Gardiner on the first ascent of the west ridge of
Mont Collon in 1876, the other member of the Mont Collon party was Arthur Cust who had made the first guideless ascent of the Matterhorn only two weeks beforehand. In 1878 Gardiner and the two Pilkington brothers started mountaineering without guides, The first guideless ascent of the
Barre des Écrins and the first ascent of
Pointe des Arcas were amongst the successes of that trip. They made further guideless alpine ascents during the summers of 1879 and 1881, revisiting the Dauphiné and climbing in the
Bernese Oberland and the
Pennine Alps. 1881 was the final season they climbed together, and also the year of Gardiner's marriage. Gardiner and the two Pilkington brothers were credited as "the first to show that the amateur mountaineer could safely undertake, without professional assistance, expeditions of the very first rank". After his marriage Gardiner shared the ascent of many high alpine peaks with his wife, these included the
Wetterhorn (both in summer and in winter), the
Mönch, and the
Jungfrau. Gardiner encountered
Coolidge at La Bérarde in the
Dauphiné Alps in 1879 and when Coolidge fell ill and had to undergo an operation in 1913 Gardiner spent much of August by his bedside in Switzerland. Gardiner served as vice-president of the
Alpine Club from 1896 to 1898 ==Significant ascents==