Pot Pourri - biodiversity in a bowl

Thought of by most people simply as a popular Christmas gift, Kew has what is believed to be the only scientific reference collection of pot pourri, built up over ten years from samples sent in for identification. It contains over 700 specimens, representing 300 species from 95 families and includes fungi and lichens.

Pot pourri mixes generally consist of 'toppers', showy ingredients such as Gardenia latifolia (papri cups) and the fruits of Aegle marmelos (bell or bael fruits) that are primarily decorative, and 'fillers' such as the curly pods of Acacia auriculiformis. Ingredients are chosen for their shapes and must be reasonably tough and easy to dye and fragrance. One of the most commonly used ingredients is Dregea macrantha (Arti pods). Many of the ingredients, such as banana stalks or parts of the palm Borassus flabellifer (Palmyra palm), are by-products of other activities. Some are harvested from the wild, but little is known about the sustainability and so Kew botanists are researching this.

Kew is discovering more about the plants used in pot pourri because of concern amongst retailers about possible health risks associated with its ingredients. The Centre for Economic Botany runs a pot pourri identification and toxicity report service. The report authenticates the species and provides information on any adverse reactions. Most of the 100 different samples a year seen at Kew have come from India. Prospective ingredients are usually labelled with common names by the supplier. These can be vague, one 'grass' from North America turned out to be Nolina texana in the plant family Dracaenaceae; while its leaves are safe, the fruits and flowers are toxic. Only a few items have had to be withdrawn, most notably the fruits of Strychnos nux-vomica (the commercial source of strychnine). Some, like the pungent chillies (Capsicum annum var. annum), are unsuitable because they can cause irritation when touched.