While there, Douglas became friends with the respected botanist William Hooker, a professor at the University of Glasgow. Hooker took Douglas along on several collecting trips around Scotland. In 1823, the Horticultural Society of London was looking for a scientific collector to advance the study and practice of cultivation of plants new to the British Isles. Hooker recommended Douglas, who had the right qualifications.
Douglas was first sent to New York to collect fruits and other interesting plants that might be cultivated in England. He collected some flowers and fruits there, but generally did not like New York as it was a busy and unsanitary place. He want on to Philadelphia which was much smaller, quieter, and more orderly. Here he met the famous Harvard botanist Thomas Nuttall, who had collected plants along the Missouri River and the Southwest.
He returned to England in January 1924 and spent the next six months cataloging his specimens. In July 1824, he returned to North America, this time to the Pacific coast. He would be under the protection of the Hudson's Bay Company, which controlled the only settlements west of the Rockies. On April 9, 1825, the ship arrived at Cape Disappointment, at the mouth of the Columbia River, via a cross-Atlantic journey that took him around Cape Horn and up the Pacific. John McLoughlin, chief factor at Fort Vancouver, took Douglas 70 miles upriver to the fort, which Douglas made his base. He agreed to let Douglas accompany any trading or trapping expeditions for the purpose of collecting specimens.
One of the first plants Douglas noted was the huge evergreen that would later become known as the Douglas fir. He was amazed by its size and uniformity. He noted that it would be a boon to the timber industry. He also collected specimens of the Sitka spruce, the sugar pine, and many others. In less than six months he traveled more than 2,000 miles and collected 499 species of plants. He carefully preserved his specimens in botanical paper. He wrote detailed descriptions of each one and classified them as best he could. Many of these plants were new to science.
