He is noted for having edited "The Illustrated Dictionary of Gardening", produced as an eight-part alphabetical series between 1884 and 1888 with a supplement, and published by L. Upcott Gill of London.

He started work at Kew in 1873, succeeding the late John Smith as Curator of the Gardens in 1886 and staying on until 1901, when ill-health forced his retirement.

1891 found him living as a widower at the Royal Gardens, Kew, together with his son, James Bell Nicholson, and his sister who acted as housekeeper.

He contributed to the Journal of Botany of 1875 with an article titled “The wild flora of Kew Gardens and Pleasure grounds”.

[2] Nicholson was an authority on oaks and maples, and was appointed as judge in the horticulture section of the Chicago Exposition of 1893.