why mediterranean in lower case? 
 

The plant distributed in the nursery trade around the world as Centaurea gymnocarpa, but likely a hybrid or polyploid mutant.


Centaurea 'Colchester White' as a border enlarge this image

A long border of Centaurea 'Colchester White'.

At a Glance



full
sun
partial
shade
well drained
soils
rich, loamy
soils
clay
soils
sandy
soils
alkaline
soils
acid
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neutral PH
soils
salty/saline
soils
evergreen
foliage
container
culture
attracts
bees
attracts
butterflies
windy
locations

Centaurea cineraria 'Colchester White'

ken…TAU…r⋅r⋅reh…ah  kih…neh…R⋅R⋅RAW…r⋅r⋅rih…ah

Asteraceæ Carduoideæ Cardueæ Centaureinæ

Has also been placed in Compositæ

Centaurea : centaureum - name for the centaury • cineraria : Latin: cinerarius - ashes, alluding to the gray foliage color

dusty miller, velvet centaurea


A garden plant usually grown under the name of C. gymnocarpa but DNA testing confirms it to be a hybrid or polyploid mutation of C. cineraria.


Synonymy: Centaurea cineraria ; Centaurea gymnocarpa Hort.; Centaurea gymnocarpa 'Colchester White' Hort.


One of a handful of plants that are routinely confused with each other due to their similar foliage color and form.  To fully understand the plants involved, see also Centaurea gymnocarpa, Centaurea cineraria, Centaurea ragusina and Jacobaea maritima.  I've placed this plant under the name 'Colchester White' which seems to be legitimate cultivar name (though not universally used today).

Contrary to the true C. gymnocarpa, the plant now grown in gardens around the world under that species name is quite vigorous, easy to grow, strikes cuttings without effort, tolerates of a wide range of soils, and has never (to our knowledge) produced seed - all indications of a hybrid or mutant plant.  And recent phylogenetic DNA testing (see box below) has shown that this plant's lineage definitely stems from C. cineraria.

New Development

June 2013

Dr. Jeffery R. Hughey or Hartnell College (Salinus, CA) offered to perform some phylogenetic testing for me on some of the plant in question.  This uses chloroplast DNA which is easier to isolate than more complex plant DNA and provides inheritance information (in the same way mitocondrial DNA show inheritance in mammals).  To perform this testing, I provided Dr. Hughey with samples, including the plants common in cultivation, collected C. gymnocarpa (courtesy of Dr. Bruno Foggi of Italy), wild-collected C. cineraria (courtesy of my nurseryman friend Olivier Filippi.

The results of this testing confirm that the garden plant is NOT C. gymnocarpa — its chloroplast DNA matches the wild C. cineraria samples.

In my research, I have discovered herbarium specimens dating from the 1920s which bear a remarkable resemblance to this currently cultivated plant.  These specimens are documented to have been collected from Le Jardin des Plants du Montpellier rather than wild populations.  Like many botanical gardens of the past, plantings were grouped by family and genus,providing ample opportunities for hybridization.  And since polyploid mutations are often more vigorous than the plants from whcih they arise, it is easy to presume that such plants could easily out-compete their wild siblings in gardens.

Author Mrs Desmond Underwood, in her popular 'Grey and Silver Plants' (1971), lists this plant as C. gymnocarpa 'Colchester White' - probably perpetuating confusion that already existed.

Recently, I've seen a 'new' plant (basically the same plant being discussed here) offered in Australia under the cultivar name of 'Silver Fountain'.  An apt name for the way the long graceful leaves arch out from the growing point, but it looks to be the same in all aspects.

A handsome gray leafed plant, with delicate and lush feathery leaves, it has become the favorite for container planting or summer bedding everywhere.  It is used to compliment flowering annuals/perennials in the same manner as other 'dusty millers' over time.  Easy to propagate and quickly producing copious foliage in a single season, growers incorporated it into their availability lists rapidly.

As a perennial in the ground in the mediterranean climates, in which it will grow year-round, it is an easy and carefree plant, which can often take far less water then gardeners provide.  Indeed, under normal irrigation practices, this plant can become quite rangy and rank in growth, flopping ungracefully with the long-stalked lavender-purple flowers appear in spring.  Grown leaner and with a more modest amount of water, a more compact and tidy form is had.  In fact, this plant is known to subsist on winter rainfall alone in some mediterranean regions.

Cuttings strike very easily, especially in the cooler days of autumn.  The plant commonly grown in gardens would not appear to set viable seed (this author has never been able to harvest any!).  This and the tremendous vigor generally seen would seem to confirm that the hybrid or mutant nature.  In contrast, plants in cultivation from wild C. cineraria colletions are sometimes problematic to grow in gardens, requiring perfect drainage and other substrate particulars.

Seán O'Hara




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Mrs Desmond Underwood - University of Reading, UK

Grey and Silver Plants; Collins, London; 1971

Many year ago I came across a very old specimen of Centaurea gymnocarpa [cineraria] growin up beside a wall in a derelict garden in Essex [presumably in Colchester]. Knowing that this species was not considered hardy, I grew some cutting and left them outside the following winter. For several years all was well, but then came the hard winter and the collapse of all the outdoor plants. So a fresh stock had to be raised from a few indoor specimens and it is interesting to note that these have never been quite so hardy and will only survive when planted on top of banks.



References


William T Stearn. 2004. Botanical Latin. Timber Press. ISBN 0881926272 / ISBN13 9780881926279 http://gimcw.org/books/bookinfo.cfm?bookid=blwts

Germplasm Resources Information Network (GRIN). National Plant Germplasm System. USDA Agricultural Research Service. Website http://www.ars-grin.gov/npgs/aboutgrin.html

Mrs Desmond Underwood. 1971. Grey and Silver Plants. Collins, London. https://books.google.com/books/about/Grey_and_silver_plants.html?id=mu5LAQAAIAAJ [accessed 4 April 2013].