Brown enrolled to study medicine at the University of Edinburgh, but developed an interest in botany, and ended up spending more of his time on the latter than the former. He attended the lectures of John Walker; made botanical expeditions into the Scottish Highlands, alone or with nurserymen such as George Don; and wrote out meticulous botanical descriptions of the plants he collected. He also began corresponding with and collecting for William Withering, one of the foremost British botanists of his day. Highlights for Brown during this period include his discovery of a new species of grass, "Alopecurus alpinus"; and his first botanical paper, "", read to the Edinburgh Natural History Society in January 1792, but not published in print in Brown's lifetime.