Nomenclature explanation for Clematis

Genus name and species name
A plant name, the botanical name, always start with the genus name. This genus name is always written with a capital and in italic, for instance :

correct = Clematis
wrong = clematis

A botanical name always exsist of 2 parts, the genus name and the species name. The species name is also written in italic but does not start with a capital, for instance :

correct = Clematis orientalis
wrong = Clematis Orientalis

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Subspecies, variety and forma
Botanical species can be further divided into lower ranks. This rank can be a subspecies (abbreviated as subsp.) or a variety (= varietas, abbreviated as var.) or a from (= forma, abbreviated as f.). In the plant name this rank is not written in capital or italic and always with its abbrevation. The botanical name attached to the rank is written in italic and never with a capital. The order is as written here, first subsp., then var. en then f., for instance :

Clematis orientalis subsp. orientalis
Clematis orientalis var. tangutica
Clematis orientalis f. pedunculata

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Cultivar
The lowest rank used is the cultivar. The term cultivar is a contraction of the words "cultivated variety".

A cultivar, the plant, needs to have a name at the moment of introduction, the cultivar name. With this cultivar name the plant can be identified. This cultivar name is a public domain, with other words, there are no legal rights attached to a cultivar name nor can be these extracted from it.

The rules about the use and application of cultivar names are described in the book "International Code of Nomenclature for Cultivated Plants", usually abbreviated as ICNCP or just “Code”.

One of the rules is that after the year 1959 no Latin can be used in a cultivar name, for instance :

correct = Clematis 'Ville de Lyon'
correct = Clematis 'Fujimusume'
wrong = Clematis 'Albina Plena'
wrong = Clematis 'Campanulina Plena'

The cultivar name can be a fantasy name, a code or a persons name, etc, for instance :

Clematis 'Anita'
Clematis 'Best Wishes'
Clematis 'Kugotia'
Clematis 'Prince Charles'
Clematis 'Zo06137'

The name of the cultivar needs to be written in between single quotation marks. All words of the cultivar name, with exception of for instance an article or a preposition, start with a capital. Cultivar names are not written in italic, for instance :

Clematis armandii 'Apple Blossom'
Clematis macropetala 'Chili'

When known that the cultivar is a selection from a botanical species then the botanical species name can be used in combination with the cultivar name, as in the examples above, but the cultivar name may also be written without the botanical species name :

Clematis 'Apple Blossom'
Clematis 'Chili'

When the cultivar can not be classified under a botanical species the cultivar name exsist of the genus name and cultivar name only, for instance :

Clematis 'Bill MacKenzie'

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Hybrids
When two botanical species are cross bred with each other and the seedlings (= the cross itself) are described scientifically, then this is a called a hybrid species name. In a hybrid species name there is always a × mark between the genus name and the hybrid species name. The × is not written in italic and always in a small size. This × mark is written against the hybrid species name, so without a space. Because of the use of computers, the × mark is read as an x (letter) so that hybrid species names end up at the end of a ABC list. This is not correct. Correct is, for instance :

Clematis armandii
Clematis ×cartmanii
Clematis ×jackmanii
Clematis patens

The first selected plant from this hybrid cross breeding as type specimen. When the hybrid is scientifically described and named, for instance Clematis ×cartmanii , then this name may not be used as the cultivar name for that plant. The type specimen need to have a cultivar name, for instance :

wrong = Clematis ‘Cartmanii’
correct = Clematis ×cartmanii 'Joe'

The type specimen of this crossbreeding can also be written without the hybrid species name, for instance :

correct = Clematis 'Joe'

If the hybrid species name is originally a scientific description of the plant (before 1959) then this hybrid species name is written as a cultivar name, for instance :

Clematis 'Aromatica'
Clematis 'Durandii'

A cultivar name is sometimes used in the nomenclature of a hybrid species name from before 1959 because this hybrid species name was often used a a botanical species name. This is mainly so with the use of Latin names, for instance : 

Clematis ×jackmanii
Clematis ×jackmanii 'Alba'
Clematis ×jouiniana
Clematis ×jouiniana 'Praecox'

Also these cultivar names can be written without its hybrid species name (Clematis 'Alba' of Clematis 'Praecox') but because these Latin names are regularly used within one genus it is correct to include the hybrid species name as part of the cultivar name :

Clematis 'Jackmanii Alba'
Clematis 'Jouiniana Praecox'

These hybrid species names were mainly applied of what we call cultivars today, so a clone (in Clematis). That means that the type specimen has to have a cultivar name and then the hybrid species name can be repeated as cultivar name, for instance :

Clematis ×jackmanii 'Jackmanii'
Clematis ×jouiniana 'Jouiniana'

Such names are also correctly written without the hybrid species name :

Clematis 'Jackmanii'
Clematis 'Jouiniana'

A way of solving nomenclature problems with Latin cultivar names as selection of a botanical species and published before 1959 is not applied in Clematis yet, for instance :

Clematis integrifolia 'Alba' = Clematis 'Integrifolia Alba'
Clematis montana 'Alba' = Clematis 'Montana Alba'

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Cultivar Groups
A cultivar may be classified in a cultivar group. The cultivar group classification is, for Clematis, different in many countries however some groups are widely used and applied like the Viticella Group.
The name of the Group is not part of the cultivar name and to keep them seperate from the cultivar name, the cultivar group name is written in between brackets, for instance :

Clematis 'Prince Charles' (Viticella Group)

From all examples used it may has become clear that names which are correct according the ICNCP are written in bold.

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Trade names and trade marks
Trade name and trade marks must be written in a different way then cultivars, for instance :

GOLDEN TIARA
Golden Tiara

The use of capital or small capital is easier for the computer keyboard then switching to another letter type.

The cultivar has to have a cultivar name and the trade name may not be used as a cultivar name :

correct = Clematis ‘Kugotia’
correct = Clematis ‘Kugotia’ GOLDEN TIARA
wrong = Clematis GOLDEN TIARA
wrong = Clematis ‘Golden Tiara’

A reason for a trade name might be that the original cultivar name, for instance a Japanese name, is not so attractive in Europe :

Clematis ‘Sho-un’ means “blue cloud” and when translated the name is :
Clematis ‘Sho-un’ BLUE CLOUD

Another reason for the use of a trade name is that when EU Plant Breeders Right is applied for the cultivar name usually is a code, for instance :

Clematis 'Evipo026'

This cultivar name is difficult to understand for the gardener and so a trade name is usually attached to the cultivar name, for instance :

Clematis 'Evipo026' DIANA’S DELIGHT

Trade names can be registered as trade mark. Trade marks for plants and flowers are registered in Class 31. No one can use this trade mark without permission of the trade mark holder. In the way the trade name is written on plant labels it is not clear if the trade name is also a trade mark. That is why the symbol ® is written with the trade mark, for instance :

Clematis 'Zostapa' STAR OF PAKISTAN®

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Plant Breeders Right
For a new introduction Plant Breeders Right can be applied in every single EU country but also for the EU as a whole. PBR is a property right for the owner of the certain cultivar. If PBR is granted then the cultivar can only be propagated by agreement of the PBR holder.

When PBR is granted then PBR is added to the cultivar name in superscript, for instance :

Clematis 'Evipo026'PBR

EU PBR can be applied for when the cultivar only has a trade name and in that process the trade names becomes the cultivar name. The EU PBR Office, CPVO, has slightly different rules then the ICNCP and today meetings are held to get all rules the same.