Use single quotation marks for quotes within quotes. Do not use single quotation marks around unusual terms (use double quotation marks) or around terms to be defined (bold these at first use if they are included in a glossary or are specifically defined in the text).
Use single quotation marks around plant variety names in running text as shown.
Example: The hybrid Agastache ‘Apricot Sunrise,’ best grown in zone 6, mingles with sheaves of cape fuchsia (Phygelius ‘Salmon Leap’).
But, do not use single quotation marks when cultivar names are written alone (without the species name), unless their absence would be confusing.
Example: Era is a widely grown cultivar of wheat.
Example: Hedra helix L. ‘Chicago’ is a popular ivy.