[2] Fumaria occidentalis is the largest fumitory to grow in the United Kingdom,[3] with flowers 12–14 millimetres (0.47–0.55 in) long.

[4] Fumaria occidentalis is an annual plant, flowering from March on the Isles of Scilly, but in May or June on the Cornish mainland.

[3] It can be locally abundant in various types of arable and waste land,[4] including field edges and Cornish hedges.

[5] In 1902, Pugsley had seen herbarium specimens that he could not assign to any British species, and encountered the plant in person in 1904 while in Cornwall "for a short holiday".

She reported that she found it on the edge of a wood at Lelant according to F. Hamilton Davey's 1909 Flora of Cornwall.