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Products > Centaurea ragusina
Centaurea ragusina - Silver-Knapweed
Image of Centaurea ragusina
[2nd Image]
Habit and Cultural Information
Category: Perennial
Family: Asteraceae (Sunflowers)
Origin: Crete (Mediterranean
Evergreen: Yes
Flower Color: Yellow
Bloomtime: Summer
Synonyms: [Centaurea candidissima, Hort.]
Height: 1-2 feet
Width: 2-3 feet
Exposure: Full Sun
Summer Dry: Yes
Deer Tolerant: Yes
Irrigation (H2O Info): No Irrigation required
Winter Hardiness: 10-15 F
Centaurea ragusina (Silver-Knapweed) - A beautiful white foliaged small cushion shaped mounding evergreen perennial/subshrub to 12 to 18 inches to tall by 2 to 3 feet wide. It has long petioled 6 in long pinnately lobed leaves with the wavy rounded lobes covered in fine white hairs arranged like tight rosettes at short branch tips - these rosettes of decoratively lobed leaves have led some to compare the look of this plant to a snowflake. From late spring through mid-summer and rising just above the foliage on solitary to few branched stems appear the showy 1 1/2 to 2 inch wide bright yellow thistle-like composite flowers, which have long disc florets and no ray ligules sitting on top of the basket-like cluster of brown scaly bracts. Plant in full sun in a well-drained soil and irrigate occasionally to very little. Listed to USDA Zone 7 in Hardy Herbaceous Perennials by Leo Jelitto and Wilhelm Schacht (Timber Press, 1985) so should be reliably cold hardy at least down to 10F. Tolerant of the wind and salt spray of seashore conditions. A very attractive small plant for use in the mediterranean climate garden - particularly nice to use for contrasting foliage with darker foliage plants. This plant is endemic to Croatia where grows on cliffs, rocks and stone walls on the islands and mainland of the central and southern Dalmatian coast. The name for the genus comes from the centaurs of Greek mythology which were claimed to have discovered the plants medicinal qualities and the specific epithet comes from the locality of Ragusa (now Dubrovnik) from where the plants Carl Linnaeus described the species in 1753 originated, though some confusion over the location had the plant originally listed as from Crete (previously the Kingdom of Candia). For this reason in the listing in the William Curtis's Botanical Magazine ("The Botanical Magazine, Or Flower-garden Displayed" Volume 14, pg. 494) called it the Cretan Centaury. Curtis also mistakenly listed the plant native the native to the isle of Candia (Crete). He also noted that it was first grown in 1714 in the garden of gardener and botanist Mary Somerset, the Duchess of Beaufort (16301715), who was notably one of England's earliest distinguished lady gardeners. Other common names include Ragusa Knapweed, Dubrovnik Cornflower and Snowflake Dusty Miller. This plant is rare and protected in it natural habitat but was once a much more common plant in horticulture, grown for border edging as the common "Dusty Miller" until replaced by other related species. While this plant is rarely discussed in modern books, the Irish-born gardener and writer William Robinson (1838-1935) wrote of this plant in The Subtropical Garden: Or, Beauty of Form in the Flower Garden, published in 1871, that "This fine and distinct plant, which has lately become one of the most popular of our flower garden ornaments, cannot be passed by in a book of fine-leaved plants. It is so abundantly use as a bedding and ribbon-plant, etc., that nothing need be said of it in these respects, but it will be seen to great advantage in single, well-grown tufts of small groups, as its silvery leaves would contrast finely with many of the dark green and glossy things recommended for this purpose". We also grow the related purple flowering Velvet Centaurea, Centaurea gymnocarpa, which is also sometimes called "Dusty Miller" and now thought to be more correctly a form of Centaurea cineraria. We thank Jose Manza, manager of Seaside Nursery in Carpinteria for providing us with our first stock specimen this very fine plant. 

This information about Centaurea ragusina displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.