John Grimshaw
Sun, 08 Apr 2007 00:34:56 PDT
Quite a few mesages have flown through cyberspace since this question was 
asked, but it needs an answer.

Are you using your "horticultural group system" like a grex in the
> orchid world?
> What would the naming convention be if we were to follow this suggestion?
> Carlo

It's probably easiest to copy out the notes in the RHS Plant Finder that 
define a group and a grex:

Within orchids, hybrids of the same parentage, regardless of how alike they 
are, are given a grex name. Individuals can be selected, given cultivar 
names and propagated vegetatively. For example Pleione Versailles gx 
'Bucklebury', where Versailles is the grex name and 'Bucklebury' a selected 

    This is a collective name for a group of cultivars within a genus with 
similar characteristics. The word Group is always included and, where cited 
with a cultivar name, it is enclosed in brackets, for example Actaea simplex 
(Atropurpurea Group) 'Brunette', where 'Brunette' is a distinct cultivar in 
a group of purple-leaved cultivars.
    Another example of a Group is Rhododendron polycladum Scintillans Group. 
In this case R. scintillans was a species that is now botanically 'sunk' 
within R. polycladum, but it is still recognised horticulturally as a Group.
    Group names are also used for swarms of hybrids with the same parentage, 
for example Rhododendron Polar Bear Group. these were formerly treated as 
grex names, a term now used only for orchids. A single clone from the Group 
may be given the same cultivar name, for example, Rhododendron 'Polar Bear'.


In the case of Arum italicum with strongly white-veined leaves, which have 
been variously known as 'Marmoratum' (= marbled) or 'Pictum' (= painted), 
there is clearly a vast number of seedlings that bear this characteristic. 
They can't all be one cultivar, but they certainly share the defining 
character of white veins and as such the Group concept is ideal. Since 
'Pictum' is an undesirable name because of the existence of the species Arum 
pictum, Marmoratum is the preferred epithet and Marmoratum Group would 
therefore be most appropriate. Within the Arum italicum Marmoratum Group are 
numerous selected cultivars (some of dubious value, mind you!) e.g. 'Winter 
Beauty', 'White Winter' and these would be written Arum italicum (Marmoratum 
Group) 'White Winter'. Seedlings from the clone 'White Winter' would then 
just blend back into the Group, unless one were sufficiently distinct to 
warrant a cultivar name.

My reservation about the Group concept is that in (let's call them) 
unparticular hands it could be used to make something seem better than it 
is, and can conceal a multitude of inferior plants. For example, the Actaea 
(formerly Cimicifuga) 'Brunette' example, the seedlings can be only just 
brown over green, but still count as Atropurpurea Group. The wise gardener 
will always go for a named selection anyway, but the less experienced might 
be seduced into getting something inferior that bears an important-sounding 
name - 'full of sound and fury, signifying nothing.'

As always, careful definition of the Group, or cultivar's characteristics is 
very important.

John Grimshaw

Dr John M. Grimshaw
Sycamore Cottage
Nr Cheltenham
Gloucestershire GL53 9NP

Tel. 01242 870567

Easter Monday 9 April, Arboretum Weekend 15-16 September
Gates open 1pm, last entry 4 pm

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