From 1821 Henslow had begun organising a herbarium of British flora, supplementing his own collecting with a network which expanded over time to include his friends and family, and the botanists William Jackson Hooker and John Hutton Balfour, as well as about 30 of his students.
In the summer of 1831 Henslow was offered a place as naturalist to sail aboard the survey ship HMS Beagle on a two-year voyage to survey South America, but his wife dissuaded him from accepting.