While working at the Natural History Museum, London she has overseen the Flora Mesoamericana inventory of Central American plants.

In 2023 she was appointed an Officer of the Order of the British Empire (OBE) and was awarded the Engler Medal in Gold by the International Association for Plant Taxonomy.

She is also an expert in other taxa within the nightshade family (Solanaceae), including the genus Nicotiana and the tribes Anthocercidae and Juanulloeae.

[2] Knapp has collected plants in Central and South America for the Missouri Botanical Garden and Cornell University, among others.

[7] In October 1999, Knapp discussed her book Footsteps in the Forest: Alfred Wallace in the Amazon on the BBC World Service's Science in Action.

[8] Knapp was an interviewed guest on BBC Radio 3's Night Waves in July 2013 in a segment about Alfred Russel Wallace.

[15] In 2009 she was presented with the Peter Raven Outreach Award for public engagement with science by the American Society of Plant Taxonomists and the UK National Biodiversity Network's John Burnett Medal.

[3] In 2022 she was awarded the David Fairchild Medal for Plant Exploration by the United States National Tropical Botanic Garden.

[18] Knapp was appointed Officer of the Order of the British Empire (OBE) in the 2023 New Year Honours for services to botany and the public understanding of science.