The rules of the European Union give two possibilities for cultivar names. The first possibility is a fantasy name. The second possibility is a code.

The following rules apply for both fantasy names and codes:

• Official lists of cultivar names are kept up by an official agency of the EC, by a member state of the EC or by a country with a contractual agreement of UPOV. For example: in the Netherlands the Dutch Inspection Service for Horticulture (Naktuinbouw) keeps up the list with names of vegetable varieties.
• The name or a part of the name may not be in use as a currency -, weight -, or measure entity. The name 'Euro’ or the code 'Euro100' are invalid names.
• A name is forbidden if it is common language and thus forms an obstruction for a third party.
• Names in use as legally protected names, for example abbreviations of international organisations, may not be used. For this reason the name Chrysanthemum 'UN dessert storm' is not permitted.
• The name may not be misleading due to a characteristic that the cultivar does not possess. A Sinningia with purple flowers may not be called 'Blue Lagoon' or 'RED 13'.
• The cultivar code or name may be reused if this code or name has not been used for the last 10 year within the same UPOV class, and if this code or name has not obtained a special reputation.
• A name is forbidden if this name does suggest an incorrect affinity. For example: Tulipa 'Parade' is an existing tulip cultivar. A new tulip variety may only have "parade" as part of its name if this cultivar shares a common affinity with T. 'Parade'.
• The competitive and superlative may not be used. For this reason the name Dracaena margarita 'Hollands Best' is not permitted.
• The cultivar name may not resemble an existing trade name too much. This regulation will prevent that a cultivar name can give the impression that it belongs to someone other than the applicant. For example: Viviane is! is a trade name for roses. A cultivar may not be called Rosa 'Viva Viviane' by someone other than the owner of the trade mark Viviane is!.
• The cultivar name or code not may not contain the name of a botanic genus or species or a part thereof. Solanum 'Hibiscus' is not permitted, because Hibiscus a is a genus name.
• A cultivar name or code may not contain a local name of a plant within the same plant class. There are 4 classes, namely agriculture, horticulture of ornamentals, tree culture and fruit cultivation. Helianthus annuus 'Yellow Lily' or 'LILYAB' are not permitted because lily is common language within the plant class horticulture of ornamentals.

The following rules apply for a fantasy name only:

• The name must at least differ in two characters from all other cultivar names within the genus or UPOV-class.
• A name contains a minimum of 3 characters. For this reason Genista 'Bo' is not permitted.
• Numbers may not be used, unless this number is an integrated part of the cultivar name. Fritillaria 'Cat 1' may not, but Fritillaria ' Henry 5' may be used.
• A cultivar name exists of a maximum of 3 words and may not be too long. Viola 'Fantasy Greenness with Blue Eye' is therefore prohibited.
• Symbols are prohibited in the cultivar name, as well as punctuation marks, under - or super script, a mix of capital and small characters or drawings. Zantedeschia 'Rembrandt!' and Zantedeschia 'Lace-pillow' are both not permitted.

The following rules only apply for a code:

• The code must at least differ in one character from all other cultivar names and codes within its genus or UPOV-class.
• It is obligatory to indicate that the deviation concerns a code and not a fantasy name.
• The cultivar code may not consist of figures only. For this reason Lycopersicon '200012' is not permitted.
• The cultivar code may not exist of 1 character only. For this reason Selaginella martensii 'Q' is not a suitable code.
• The cultivar code may not contain symbols, punctuation marks, under - or super script or drawings. The code Ixora 'Qui-6' is not permitted.
• The cultivar code contains a maximum of 10 characters. For this reason Spatiphyllum 'Hae 20010074' is not suitable.
• The cultivar code contains a maximum of 4 groups of characters and figures. For this reason the code Anthurium ' An2t01a5' is not acceptable.