The term grex (pl. greges), derived from the Latin noun grex, gregis meaning flock, has been coined to expand botanical nomenclature to describe horticultural hybrids of orchids, based solely on their specified parentage. It is a type of the "Group" category, which is used to describe cultivated plants in practical ways that are not necessarily related to their biological classification.
A grex may be:
Linnean treatment of natural hybrids: the nothospecies
Naturally occurring interspecific hybrids, or nothospecies, are given Linnean binomials with the multiplication sign "×" between the generic epithet and the nothospecific epithet. An offspring of the nothospecies, either with the nothospecies or either of the parental species as the other parent, has the same nothospecific name. That is, the nothospecific binomial is an alias for a list of the ancestral species. The × symbol is not italicised.
For example, a naturally produced hybrid between Cattleya warscewiczii Rchb.f. 1854 and Cattleya aurea Linden 1883 would be called Cattleya ×hardyana Sander 1883 or Cattleya × hardyana. An offspring of a Cattleya × hardyana pollenized by another Cattleya × hardyana would also be called Cattleya × hardyana. Cattleya × hardyana would also be the name of an offspring of a Cattleya × hardyana pollenized by either a Cattleya warscewiczii or a Cattleya aurea, or an offspring of either a Cattleya warscewiczii or a Cattleya aurea pollenized by a Cattleya × hardyana
Horticultural treatment of greges
A non-specific grex is initially produced by the deliberate hybridization of two different greges, and is treated as if it were some new species.
When a hybrid cross is made, all of the seedlings grown from the resulting seed pod are considered to be in the same grex. Any additional plants produced from the hybridization of the same two parental greges also belong to the grex. All of the members of a specific grex may be loosely thought of as "sister plants", and just like the brothers and sisters of any family, may share many traits in common or look quite different from one another. This is due to the randomization of genes passed on to progeny during sexual reproduction. The hybridizer who created a new grex may choose to register the grex with a registration authority, in which case the grex must be named. If two members of the same grex produce offspring, the offspring receive the same grex name as the parents. Individual plants may be given cultivar names to distinguish them from siblings in their grex. Cultivar names are usually given to superior plants with the expectation of cloning that plant; all clones of a plant share a cultivar name.
The non-specific gregaric name differs from a specific name in that the gregaric part of the name is capitalized, is not italicized, and may consist of up to four words; according to the International Code of Nomenclature for Cultivated Plants it must be followed by the word "grex" which is not capitalized or italicized.
For example: an artificially produced hybrid between Cattleya warscewiczii and C. dowiana (or C. aurea, which the RHS, the international orchid hybrid registration authority, considers to be a mere variety of and therefore synonymous with C. dowinana) is called C. Hardyana grex. An artificially produced seedling that results from pollenizing a C. Hardyana grex with another C. Hardyana grex is also a C. Hardyana grex. However, the hybrid produced between C. Hardyana grex and C. dowiana is not C. Hardyana grex, but C. Prince John grex. Similarly, the artificial hybrid produced between C. Hardyana grex and C warscewiczii is C. Eleanor grex. These relationships can be described in the following manner:
C. Hardyana grex = C. warscewiczii × C. dowiana
C. Eleanor grex = C. Hardyana grex × C. warscewiczii
C. Prince John grex = C. dowiana × C. Hardyana grex
In informal usage, "grex" is often omitted (e.g., Cattleya Hardyana), but this can lead to ambiguity.
An example of a complex-hybrid grex is Phanaenopsis Baldan's Kaleidoscope grex (sometimes also labeled a cultivar, as Phalaenopsis 'Kaleidoscope').
Due to the maintenance of many interspecific (and even intergeneric) barriers in the Orchidaceae by pollinator behavior, it is easy to produce complex interspecific and even intergeneric hybrid orchid seeds: all it takes is a human motivated to use a toothpick, and proper care of the mother plant as it develops a seed pod. Germinating the seeds and growing them to maturity is another story.
- Brickell, C.D.; Braun, B.R.; Hetterscheid, W.L.A.; Leslie, A.C.; McNeill, J.; Trehane, P.; Vrugtman, F.; Wiersema, J.H. 2004. International Code of Nomenclature for Cultivated Plants (I.C.N.C.P. or Cultivated Plant Code) incorporating the Rules and Recommendations for naming plants in cultivation, Seventh Edition, Adopted by the International Union of Biological Sciences Commission for the Nomenclature of Cultivated Plants. International Society for Horticultural Science and International Association for Plant Taxonomy. Article 3.3
- International Code for Botanical Nomenclature, Vienna Code (2006), Article H.1
- For a partial discussion of nothotaxa, see http://www.rhs.org.uk/NR/rdonlyres/C765B912-AA2C-44F5-B1C4-209333E99047/0/orrevjan03.pdf the online version of "New Orchid Hybrids September - November 2002 Registrations" The Orchid Review 111 1249 (January - February 2003), The Royal Horticultural Society.</a>
- A page to resolve grex names: http://www.rhs.org.uk/plants/registerpages/orchid_parentage.asp