Croall was a joiner, born in Brechin, who in middle life became a schoolmaster in Montrose and then in Hillside.

A keen field botanist, in 1837 he found Lemna trisulca (Star Duckweed) at Stone of Morphie – a first for North Scotland. In the following year he was admitted as Associate member of the Botanical Society of Edinburgh and in 1848 he publishes an account of a “Five Hours Ramble on the Findhorn” in the The Phytologist.

A measure of his regard in the botanical community of Britain was a commission in 1854 from W.J. Hooker to collect a set of plants of Braemar for Queen Victoria and Prince Albert. He published the “Plants of Braemar” the following year in five fascicles (volumes of 100 dried plants). He made a similar set of the “Flora of Angus & Mearns” amounting to seven fascicles with over six hundred specimens. These he left to the Montrose Natural History and Antiquarian Society of which he was a member.

Under the auspices of the MNHAS, in 1855 he, together with James Gilchrist (medical superintendent at the Montrose Royal Asylum), instituted a series of botanical and geological classes in Montrose for young men in an effort to promote natural history amongst those who might not otherwise be exposed to higher education.

Croall's interests were not only in higher plants and in 1859 he published “Nature Printed British Seaweeds” with W.G. Johnstone which ran to 4 volumes.

In 1863 he became librarian to the Museum and Herbarium at Derby. In 1874 he become the first Curator of the Smith Institute in Stirling, now the Stirling Smith Art Gallery & Museum, and held that post until his death in 1884. While in Stirling he also taught botany and natural history at Stirling High School and established the Stirling Field Club in 1878 (which later became Stirling Natural History and Archaeology Society) and was its President.

He was active until an illness in the last year year of his life and he submitted his last paper to the SFC, “Weeds – what they are, and what to do with them”, in November 1883.

Obituaries appeared in many papers. The Dundee Evening Telegraph said “his stores of information were of much service to the members [of the Stirling Field Club], while his infectious enthusiasm quickened their zeal.” and “His modesty may be said to have kept him back from taking the position in life to which his talents entitled him.”

The Dundee Courier obituary said “By the death of Mr Croall science has lost an intelligent and painstaking worker, whose abilities were worthy of more recognition than they have yet received ...”