Onopordum acanthium
(scotch thistle)

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Qaderi MM, 2002. Pre- and post-dispersal factors affecting cypsela dormancy in Scotch thistle, Onopordum acanthium (Asteraceae). PhD thesis. University of Western Ontario, London, Canada.

Qaderi MM; Cavers PB, 2000. Variation in germination response within Scotch thistle, Onopordum acanthium L., populations matured under greenhouse and field conditions. E^acute~coscience, 7(1):57-65; 57 ref.

Qaderi MM; Cavers PB, 2003. Effects of dry heat on the germinability and viability of Scotch thistle (Onopordum acanthium) cypselas: interpopulation and interposition variation. Canadian Journal of Botany, 81:684-697.

Qaderi MM; Cavers PB; Bernards MA, 2003. Isolation and structural characterization of a water-soluble germination inhibitor from Scotch thistle (Onopordum acanthium) cypselas. Journal of Chemical Ecology, 29:2407-2420.

Qaderi MM; Cavers PB; Bernards MA, 2003. Pre- and post-dispersal factors regulate germination patterns and structural characteristics of Scotch thistle (Onopordum acanthium) cypselas. New Phytologist, 159(1):263-278; many ref.

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Scottish Flower’s and Thistles by Urban Blooms, Glasgow

Beautiful blooms with a Scottish twist make up one of our favourite collections. This collection of products includes the national flower of Scotland… the thistle to give off that highland feel. We have a varierty of arrangements such as baskets, pots, watercans and bouquets. These blooms are created by us and hand delivered by our deliverers of happiness as we like to call them? We deliver throughout Glasgow and surrounding area’s such as Rutherglen, Cambusland, Givanhill, Hillhead and Patrick. Let us take care of your flower delivery and send thistle bouquets today in Glasgow by placing your order online or call us on 0141 8167000

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Sunday – June 01, 2014

From: Elgin, TX
Region: Southwest
Topic: Plant Identification, Problem Plants, Herbs/Forbs
Title: Giant Thistle-Like Plant from Elgin, TX
Answered by: Barbara Medford


I have a giant thistle like plant in my field we have been unable to identify. It looks like a milk thistle but it is short..only about a foot tall..stocky…and the flowers are giant..about 6 to 8 inches accross. There are two to three blooms on each plant. It looks and seeds just like thistle. The flowers are usually white or purple…help. Thank you.


We are sorry, that is not enough information for us to identify your plant, especially since there is always a good chance that it is non-native. The Lady Bird Johnson Wildflower Center, home of Mr. Smarty Plants, is committed to the growth, propagation and protection of plants native not only to North America but also to the area in which those plants are being grown; in your case, Bastrop or Travis County. However, it is more likely you are wondering if you should get rid of it. In most cases, the answer to that is YES! We have answered similar questions several times during the last few years, not to mention in the last few weeks, so apparently this is a bad year for them. We are going to refer you first to a previous Mr. Smarty Plants answer also from Central Texas, which has more links to other information, including getting rid of the darn things.

In addition to those links, here is a link to the Texas A&M AgriLife Extension Office for Smith County on Thistle Control. While Smith County is in East Texas, the information is still good. Also, click on this link to take you to Google images of Texas thistles, a LOT of them. If you see a picture there that looks like your thistle, click on the picture and you will get some information on what it is. You can take that scientific name and find it either on our Native Plant Database or the Internet. Doesn’t really make a whole lot of difference, the techniques are all pretty much the same.

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Cotton Thistle

Onopordum acanthium

  • Name also: Scotch Thistle, Scottish Thistle, Scotch Cottonthistle
  • Family: Daisy Family – Compositae, subfamily Carduoideae
    (formerly Aster Family – Asteraceae)
  • Growing form: Biennial herb.
  • Height: 50–200 cm (20–80 in.). Stem covered with strong spines, very widely winged, rough, densely white-haired all over.
  • Flower: Flowers form 4–7 cm (1.6–3 in.) wide, single flower-like capitula surrounded by involucral bracts. Capitulum lacks ray-florets, disk florets light purple–red, tubular. Stamens 5. Gynoecium composed of 2 fused carpels. Involucre virtually spherical, involucral bracts narrowly ovate, hard, spine-tipped, hairy. Capitula solitary or in small groups in crown branches.
  • Leaves: Alternate, stalkless, decurrent. Blade ovate–broadly lanceolate, large-toothed lobes, covered in spines, tomentose.
  • Fruit: Grey-brown, black-dotted, 4–5 mm (0.16–0.2 in.) long achene with unbranched, reddish, 7–9 mm (0.28–0.35 in.) long hairs on tip.
  • Habitat: Yards, heaps of earth, roadsides, waste ground, rubbish tips, harbours and ballast soil deposits. Also ornamental.
  • Flowering time: July–September.

Spiny cotton thistle is one of the Nordic Countries’ largest and most strongly-spined herbs. Its large size, densely white-haired stem and leaves and purple capitula also make it one of the most beautiful thistles. Despite its size it is a biennial: the leaf rosette emerges in the autumn and a stout tap root grows and serves as a food store, then in the second year the flowering stem grows. The species follows cultivation and spread to Europe, where it grows in inhabited areas, especially sunny places with rich soil. It favours dry summers that are typical of the Mediterranean area and is a problematic alien in temperate climates. Finland’s cold climate has so far prevented cotton thistle from establishing a firm grip in our nature, although it would appear to have put down firm roots in Sweden. As an alien and on the other hand cultivated ornamental it can be found here and there across almost the whole of the southern half of Finland, in inhabited areas, around buildings and beside roads and coastal banks.

Cotton thistle is also the national flower of Scotland. According to legend, the Scandinavian-born Normans’ landing troops were coming to attack the Scots one night when an unlucky soldier stood on the leaf rosette of a cotton thistle. His cry warned the defenders in time, and the grateful Scots adopted the cotton thistle as the national flower. This good story might have something behind it, but it is also folklore: cotton thistle had not arrived yet in the Middle ages on Scotland’s moors, but thanks to its frightful spines it has been later been chosen as the hero of the tale.

Other species from the same family

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Identifying Scotch Thistle – Tips For Managing Scotch Thistle Plants

Beautiful but treacherous, the Scotch thistle is the bane of farmers and ranchers everywhere — but it can also make a huge mess in your home garden. Find out what to do about these plants in this article.

Identifying Scotch Thistle

Scotch thistle plants (Onopordum acanthium) boast amazing blooms atop their towering stems, but this invasive species has become a menace to livestock across the country. Its ability to act as a living barbed wire, preventing cows, sheep and other animals from reaching valuable water sources, has earned the title of noxious weed in most states. Even though it’s not as big of a problem for home gardeners, managing Scotch thistle in your landscape is important in the battle against this troublesome plant.

Although it’s a familiar plant to anyone living in a rural area, Scotch thistle is actually an import from Europe and Asia, used as an ornamental plant in the 19th Century. Those early gardeners had no idea the trouble they

would unleash with their pretty thistles. The adaptability of this plant is one of its most frightening features. For example, the life cycle of Scotch thistle can change based on the climate, so it may be an annual in one area, but a biennial or short-lived perennial in others.

Positive identification of a Scotch thistle is easy – the sharp-edge, hairy leaves are a dead giveaway. Rosettes of leaves can reach up to six feet across and stems may grow from six to eight feet tall. The breathtaking globe-shaped purple flowers are loved by many, but the seeds they produce can survive in the soil for up to 20 years. Considering that plants produce up to 40,000 seeds, that can create a pretty serious infestation for a long time.

Scotch Thistle Control

As much as Scotch thistle information makes them out to be true monsters of the plant world, they’re surprisingly easy to control in a small scale, which is typically how you’ll find them in the home garden. A few Scotch thistles won’t put up much of a fight, but make sure if you cut them down once they’ve started flowering to burn or bag that flower.

Unlike most plants, Scotch thistle flowers can produce ripe seeds even after being severed from the stem.

The best time to treat Scotch thistle is when it’s still just a rosette on the ground, then a thorough coating of weed killer is all you need. If you’re not ready to break out the herbicide, or your Scotch thistles are in a delicate area, you can hand dig them. Just be sure to wear thick gloves to protect against their sharp thorns.

Note: Chemical control should only be used as a last resort, as organic approaches are safer and much more environmentally friendly.

  • Preventing seed production is the first line of defense for invasive species. Cut off all plant tops bearing flower heads or buds, and carefully bag and dispose of them in the garbage, do not compost.
  • Because it reproduces by seed, Scotch Thistle can be controlled by mechanical, chemical and cultural methods. Severing the roots of the rosette or the plant will kills it. Small infestations can be pulled by hand.

  • Mowing makes the stand more uniform, which makes herbicide more effective, but mowing alone will not kill the plant. Applying herbicides to rosettes is very effective.

  • Spot spraying with an herbicide containing the active ingredient glyphosate is effective. Glyphosate is non-selective however, and will injure any plants it comes in contact with. Spot applications should be in spring, when plants are actively growing and up to when the flowering stem bolts. Plants sprayed after buds develop are harder to kill and may still produce viable seeds, despite plant damage.

  • Selective, translocated herbicides containing the active ingredients such as aminopyralid, 2, 4 D, or dicamba are also effective on Scotch Thistle. These herbicides will not harm grass and can be used around livestock (provided all label precautions are followed).
  • When using herbicides, carefully read and follow all label instructions and obey all label precautions. (Note: pesticide product registration is renewed annually and product names and formulations may vary from year to year.)
  • To minimize any harmful impact on bees and other pollinators, timing is important. Ideally, treat plants before blooming. If treatment after blooming is necessary, do control work early in the morning, or in the evening when bees are less active.

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