A sport, also known as a break, is a genetic mutation which causes a change in the appearance of a plant. The change can occur in the flowers (eg coloured flecks), foliage colour (eg variegation) or fruit (eg a different colour).

Often the plant will revert back to its original form the following year, however some sports are propagated from in order to form a new cultivar of that plant. For example Narcissus ‘Abba’ (a double flowered daffodil) was discovered growing as a sport of N. ‘Cragford’ (a single).