How Are Orchid Hybrid Names Determined? The Mechanism of RHS International Registration

The labels on commonly cultivated orchids often display cross names like "○○ × △△" or cultivar names written as "○○". In fact, these names are not chosen freely by breeders, but instead exist within a system centrally managed by the Royal Horticultural Society (RHS) as an international registration authority. The RHS serves as the International Cultivar Registration Authority (ICRA) for orchid hybrids and continues to record the names of new crosses created worldwide. In this column, we will explore how "grex names" and "cultivar names"—terms you encounter when purchasing or researching orchids—are determined and registered.

What is a grex name? — The collective name for a cross

To understand orchid hybrid names, the first concept to grasp is that of the "grex." A grex is a collective name given to all seedlings (offspring grown from seed) produced from the same two parent plants crossed together. For example, if a new grex name is assigned to a Cattleya cross, all plants produced from that cross share the same grex name. In other words, a grex name does not refer to an individual plant, but rather to the "lineage and combination of that cross"—thinking of it this way makes it easier to understand.

On the other hand, when an individual plant is selected from within a grex for its superior flower form, color, size, and other traits, and is propagated as an identical clone through division or micropropagation, an additional "cultivar name (clone name)" is assigned to identify that specific plant. By international convention, cultivar names are enclosed in single quotation marks and written after the grex name as the standard format. Understanding the distinction—that a grex name refers to the "blueprint" of the cross, while a cultivar name refers to a specific "individual" plant selected from it—makes it easier to interpret orchid labels.

From Sanders List to Modern RHS Registration

The practice of registering orchid hybrids has a long and layered history. Originally, a British horticultural company called Sander's compiled a registry called "Sander's List of Orchid Hybrids" that collected and organized records of orchid hybrids created around the world. The list's first edition was published in 1946, and it continued to be widely consulted as the registration authority for orchid hybrids.

From 1961 onward, the RHS formally took over these registration duties and has continued to manage orchid hybrid name registration to the present day. Today, this registry is published as the online database "International Orchid Register," allowing anyone to search the vast collection of hybrid records registered by breeders worldwide. However, detailed information about the registration history, dates, and the scope of records from earlier periods cannot be fully covered in this column summary. For accurate information, we recommend consulting the official RHS International Orchid Register directly.

Who Registers and How?

When a breeder creates a new orchid cross, the standard procedure is to assign it a name and submit a registration application to the RHS. Specifically, the breeder submits information about the cross's parents (pollen parent and seed parent) and the desired new grex name through the online registration system provided by the RHS (the International Orchid Register).

The submitted name is checked to ensure it does not duplicate any already-registered hybrid names and that it complies with naming conventions. If no issues are found, it is officially added to the database. This system prevents confusion by ensuring that the same cross does not receive multiple different names worldwide, or that different crosses do not receive the same name. In genera with active breeding programs such as Paphiopedilum and Cymbidium, new crosses are registered daily, and the International Orchid Register is continuously updated.

How Understanding the Registration System Changes How You Read Labels

Knowing about this registration system changes how you interpret the names written on orchid labels. A grex name indicates which cross a plant comes from. When a cultivar name in single quotation marks is also listed, it means that plant is an especially selected clone within that grex. Even in widely cultivated genera like Phalaenopsis (moth orchids), tracing the breeding lineage reveals that modern cultivars exist as a result of these accumulated international registrations.

When selecting an orchid, taking time to carefully examine its label name might help you appreciate how that single plant represents the culmination of breeding and registration efforts by breeders worldwide. At botachoku, you can purchase orchids grown by growers across the country directly online. We plan to continue introducing the history and background of orchid crosses and naming in future columns.