Investigation of some factors affecting peppermint oil production in Canterbury : A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in the University of Canterbury

Abstract

Peppermint (Mentha piperita) is a perennial plant and is considered to be a natural hybrid of spearmint (Mentha spicata) and watermint (Mentha aquatica). It is normally sterile, rarely sets seed, and propagates vegetatively. The most extensively grown variety today is the Mitcham strain because of its high yield and good qaality of peppermint oil when grown under suitable conditions. The present study which covered 2 seasons was designed to obtain information under Canterbury conditions regarding: (1) the relationship between the date of harvest and the yield and quality of peppermint oil, (2) the effect of the quantity and time of application of nitrogen fertiliser on the production and quality of peppermint oil, and (3) the influence of the amount of irrigation on peppermint oil. A study was also initiated on the feasibility of achieving two harvests of peppermint in a single growing season. This possibility of obtaining two crops in one growing season had been pointed out by Foong (1973).