Scotch Cotton Thistle, Scotch Thistle, Heraldic Thistle
Onopordum acanthium

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Onopordum (on-OH-por-dum) (Info)
Species: acanthium (a-KANT-tee-um) (Info)

Category:

Biennials

Height:

4-6 ft. (1.2-1.8 m)

Spacing:

24-36 in. (60-90 cm)

Hardiness:

USDA Zone 3a: to -39.9 C (-40 F)

USDA Zone 3b: to -37.2 C (-35 F)

USDA Zone 4a: to -34.4 C (-30 F)

USDA Zone 4b: to -31.6 C (-25 F)

USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:

Full Sun

Danger:

Plant has spines or sharp edges; use extreme caution when handling

Bloom Color:

Purple

Bloom Time:

Mid Summer

Late Summer/Early Fall

Foliage:

Grown for foliage

Silver/Gray

Velvet/Fuzzy-Textured

Mottled

Other details:

May be a noxious weed or invasive

This plant is attractive to bees, butterflies and/or birds

Average Water Needs; Water regularly; do not overwater

Provides winter interest

Soil pH requirements:

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Patent Information:

Non-patented

Propagation Methods:

From seed; direct sow outdoors in fall

From seed; winter sow in vented containers, coldframe or unheated greenhouse

From seed; sow indoors before last frost

From seed; direct sow after last frost

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds

Wear gloves to protect hands when handling seeds

Properly cleaned, seed can be successfully stored

Regional

This plant has been said to grow in the following regions:

Skull Valley, Arizona

Redlands, California

Aurora, Colorado

Moosup, Connecticut

Red Hook, New York

Fort Worth, Texas

show all

Gardeners' Notes:

3
positives
2
neutrals
1
negative
RatingContent
Neutral

On Oct 31, 2014, coriaceous from ROSLINDALE, MA wrote:

Fourteen states have banned this as a noxious weed of public concern.

Please check your state laws before planting this species.

If you grow it, know that the plant looks shabby after flowering, so cutting it down or pulling it out then not only keeps it from shedding seed but also keeps your garden looking good.

Positive

On Jul 25, 2010, DMersh from Perth
United Kingdom (Zone 7b) wrote:

In the UK this is one of the less common thistles being rarer than Creeping Thistle or Spear Thistle. In spite of its name this is not the the thistle that appears in Scottish heraldry, the Spear Thistle is the one used as an emblem of Scotland.
The seeds are relatively large compared to other thistles and are not dispersed by wind, they just fall to the ground around the plant.

Neutral

On Dec 27, 2006, frostweed from Josephine, Arlington, TX (Zone 8a) wrote:

Scotch Cotton Thistle, Scotch Thistle, Heraldic Thistle Onopordum acanthium is naturalized in Texas and other States and is considered an invasive plant in Texas.

Negative

On Nov 12, 2004, cherishlife from Pocola, OK (Zone 7a) wrote:

Arkansas has this plant listed as a noxious weed in the usda.gov site.

Positive

On Jul 8, 2002, lupinelover from Grove City, OH (Zone 6a) wrote:

This is a great plant for a few purposes: it makes an impenetrable hedge or barrier -- no one would dare its thorns. Also wonderful plant to attract finches. Seeds do not blow as Canadian or bull thistle, but drop straight down from plant, so unwanted seedlings are easy to hoe out.

Do not cold compost this plant; takes years for thorns to disintegrate. Hot-compost only.

Positive

On Sep 20, 2001, poppysue from Westbrook, ME (Zone 5a) wrote:

Scottish thistle is also called cotton thistle or Scott's thistle. Plants produce a large rosette of spiny, silvery-white foliage the first year of growth. The following year thick triangular stems grow up to 6 feet tall and are topped with lavender thistle-like flowers. They prefer full sun and well-drained soil. It may become a weed if plants are allowed to self seed freely. Trim the flower heads before they set seed to control it.