Onopordum acanthium
(scotch thistle)

Top of page

Abuharfeil NM; Maher S; Kleist S von; von Kleist S, 2001. Augmentation of natural killer cell activity in vivo against tumor cells by some wild plants from Jordan. Phytotherapy Research, 15:109-113.

Alex JF, 1992. Ontario weeds. Publ. No. 505. Toronto, Canada: Queen’s Printer for Ontario.

Alonso-Zarazaga MA; Sanchez-Ruiz M, 2002. Revision of the Trichosirocalus horridus (Panzer) species complex, with description of two new species infesting thistles (Coleoptera: Curculionidae, Ceutorhynchinae). Australian Journal of Entomology, 41(3):199-208; 26 ref.

Auld BA; Medd RW, 1987. Weeds – An Illustrated Botanical Guide to the Weeds of Australia. Melbourne, Australia: Inkata press.

Auld BA; Menz KM; Medd RW, 1978. Bioeconomic model of weeds in pastures. Agro-Ecosystems, 5(1):69-84

Austin MP; Groves RH; Fresco LMF; Kaye PE, 1985. Relative growth of six thistle species along a nutrient gradient with multispecies competition. Journal of Ecology, 73(2):667-684

Batson WT, 1975. Genera of the Eastern Plants, edition 2. Columbia, South Carolina, USA: The State Printing Co.

Beck KG, 1999. Biennial thistles. In: Sheley RL, Petroff JK, eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, Oregon, USA: Oregon State University Press, 145-161.

Bentham G; Hooker JD, 1904. Handbook of the British flora. London, UK: L. Reeve and Co.

Boeleke O, 1986. Plantas vasculares de la Argentina: nativas y exóticas. Buenos Aires, Argentina: Editorial Hemisferio Sur SA.

Boissier E, 1875. Flora Orientalis, Vol. 3. Geneva & Basle, Switzerland: H. Georg.

Bremness L, 1989. The Complete Book of Herbs. Montreal, Canada: The Reader’s Digest Association (Canada) Ltd.

Briese DT, 1988. Weed status of twelve thistle species in New South Wales. Plant Protection Quarterly, 3(4):135-141

Briese DT, 1989. Natural enemies of carduine thistles in New South Wales. Journal of the Australian Entomological Society, 28(2):125-134.

Briese DT, 1996. Landholder attitudes to Onopordum thistles and their control: a preliminary view. Plant Protection Quarterly, 11(SUP2):281-284; 5 ref.

Briese DT, 1996. Potential impact of the stem-boring weevil Lixus cardui on the growth and reproductive capacity of Onopordum thistles. Biocontrol Science and Technology, 6(2):251-261; 17 ref.

Briese DT; Thomann T; Vitou J, 2002. Impact of the rosette crown weevil Trichosirocalus briesei on the growth and reproduction of Onopordum thistles. Journal of Applied Ecology, 39(4):688-698; 22 ref.

Britton NL; Brown A, 1970. An illustrated flora of the northern United States and Canada, Vol. III, edition. New York, USA: Dover Publications, Inc.

Caballero A, 1984. Floras of the world, Vol. 3. Flora Analítica de Espana. Koenigstein, West Germany: Koeltz Scientific Books.

Cabrera AL, 1971. Compositae. In: Correa MN, ed. Flora Patagonica. Part VII. Buenos Aires, Argentina: Coleccion Cientifica del INTA, Instituto Nacional de Tecnologia Agropecuaria, 283- 285.

Callihan RH; Miller TW, 1994. A Pictorial Guide to Idaho’s Noxious Weeds. Boise, Idaho, USA: Idaho Department of Agriculture.

Cavers PB; Groves RH; Kaye PE, 1995. Seed population dynamics of Onopordum over 1 year in southern New South Wales. Journal of Applied Ecology, 32(2):425-433

Correll DS; Johnston MC, 1970. Manual of the vascular plants of Texas. Renner, Texas, USA: Texas Research Foundation.

Cratty RI, 1932. The Iowa Flora. Iowa, USA: Iowa State College.

Curtis WM, 1963. The Student’s Flora of Tasmania, Part 2. Tasmania: LG Shea, Government Printer.

Czerepanov SK, 1995. Vascular Plants of Russia and Adjacent States (The Former USSR). Cambridge, UK: Cambridge University Press.

Darbyshire SJ, 2003. Inventory of Canadian agricultural weeds. Ottawa, Canada: Agriculture and Agri-Food Canada.

Davidson S, 1990. Goats help eliminate thistles. Rural Research, No. 147:16-19; 3 ref.

Deam CC, 1940. Flora of Indiana. Indianapolis, Indiana, USA: Wm. B. Burford Printing Co.

Delfosse ES, 1990. Biological control of weeds and the dried fruits industry. Plant Protection Quarterly, 5(3):91-97

Fisher TR, 1988. The Dicotyledoneae of Ohio. Columbus, Ohio, USA: Ohio State University Press.

French K; Burrill LC; Butler TV, 1999. Problem Thistles of Oregon. Corvallis, Oregon, USA: Oregon State University.

Georgieva J; Lakova M; Spirkov D, 1973. Further study of the form obtained after crossing Helianthus annuus L. with Onopordum acanthium L. Genet Sel, 4:397-408.

Gigieniva EI; Umarov AU, 1981. Nonglycerids seed cover lipids of Artemisia absinthium and Onopordum acanthium. Khimiya Prirodnykh Soedinenii, 0:154-157.

Glasby JS, 1991. Dictionary of Plants Containing Secondary Metabolites. London, UK: Taylor and Francis Ltd.

Great Plain Flora Association, 1986. Flora of the Great Plains. Kansas, USA: University Press of Kansas.

Grieve BJ; Blackall WE, 1975. How to Know Western Australian Wildflowers. Nedlands, Western Australia: University of Western Australia Press.

Guinochet M; Vilmorin R, 1982. Flore de France. Fascicule 4. Paris, France: Centre National de la Recherche Scientifique.

Hamilton GH, 1943. Plants of the Niagara Parks System of Ontario. Toronto, Canada: The Ryerson Press.

Harden GH, 1992. Flora of New South Wales, Vol. 3. Kensington, NSW, Australia: New South Wales University Press.

Haughton CS, 1978. Green Immigrants: the Plants that Transformed America. New York, USA: Harcourt Brace Jovanovich, Inc.

Hilston NW, 1969. Weeds of Wyoming. Bulletin 498. Laramie, Wyoming, USA: University of Wyoming, Agricultural Experiment Station.

Holm L; Pancho JV; Herberger JP; Plucknett DL, 1979. A Geographical Atlas of World Weeds. Toronto, Canada: John Wiley and Sons Inc.

Holmgren AH; Andersen BA, 1970. Weeds of Utah. Logan, Utah, USA: Utah State University.

Hooper JF; Young JA; Evans RA, 1970. Economic evaluation of Scotch thistle suppression. Weed Science, 18:583-586.

Hubbert J, 1867. Catalogue of the flowering plants and ferns indigenous to, or naturalized in Canada. Montreal, Canada: Dawson Brothers.

Hyde-Wyatt BH, 1968. Cotton thistle. Tasmania Journal of Agriculture, 39:43-46.

Hyde-Wyatt BH; Morris DI, 1980. The noxious and secondary weeds of Tasmania. Tasmania, Australia: Department of Agriculture.

Jessop JP; Toelken HR; eds, 1986. Flora of South Australia, edition 4. Vol. 3, 1634-1635.

Joley DB; Woods DM; Pitcairn; MJ, 1998. Field studies to examine growth habit and population resurgence of Scotch thistle in northern California. CDFA biological control program: Annual report. California, USA: California Department of Food and Agriculture.

Jones GN; Fuller GD, 1955. Vascular plants of Illinois. Urbana, Illinois, USA: The University of Illinois Press.

Julien MH; Griffiths MW, 1998. Biological control of weeds: a world catalogue of agents and their target weeds. Biological control of weeds: a world catalogue of agents and their target weeds., Ed. 4:x + 223 pp.

Keil DJ; Turner CE, 1993. Onopordum. In: Hickman JC, ed. The Jepson Manual: Higher Plants of California. Berkeley and Los Angeles, USA: University of California Press, 320.

Lehr JH, 1978. A Catalogue of the Flora of Arizona. Phoenix, Arizona, USA: Desert Botanical Garden.

Lindley DC, 2003. Horizon Herbs, LLC. Williams, Oregon, USA. http://www.horizonherbs.com.

Matson NP, 2000. Biodiversity and its management on the National Elk Refuge, Wyoming. Bulletin Series – Yale School of Forestry and Environmental Studies, No.104:101-138.

Matthei O; Marticorena C, 1990. Weeds of the family Asteraceae new for the flora of Chile. Gayana, Botanica, 47:57-63.

Matthews LJ, 1975. Weed Control by Chemical Methods. Government Printer. Wellington New Zealand, 710 pp.

McCarty MK; Scifres CT; Robinson LR, 1984. A descriptive guide for major Nebraska thistles. Publication, Nebraska Agricultural Experiment Station, 493:1-27.

Mehrhoff LJ; Metzler KJ; Corrigan EE, 2003. Non-native and Potentially Invasive Vascular Plants in Connecticut. Storrs, Connecticut, USA: University of Connecticut, Center for Conservation and Biodiversity.

Meier LR, 1995. Variation in seeds of Onopordum acanthium. MSc thesis. University of Western Ontario, London, Canada.

Michael PW, 1968. Control of the biennial thistle, Onopordum, by amitrole and five perennial grasses. Australian Journal of Experimental Agriculture and Animal Husbandry, 8:331-339.

Michael PW, 1996. Necessary background for studies in the taxonomy of Onopordum in Australia. Plant Protection Quarterly, 11(SUP2):239-241; 2 pp. of ref.

Minehan D, 1996. Practical problems with existing thistle control: where is more research needed?. Plant Protection Quarterly, 11(SUP2):279-280.

Moore RJ; Frankton C, 1962. Cytotaxonomic studies in the tribe Cynareae (Compositae). Canadian Journal of Botany, 40:281-293.

Moore RJ; Frankton C, 1974. The Thistles of Canada. Monograph, Research Branch, Canada Department of Agriculture, No. 10:112 pp.

Mucina L, 1989. Syntaxonomy of the Onopordum acanthium communities in temperate and continental Europe. Vegetatio, 81:107-115.

Nebraska Department of Agriculture, 1979. Nebraska Weeds. Lincoln, Nebraska, USA: Department of Agriculture, Weed Division.

Nevskii VP, 1929. Aphids of Central Asia. Tashkent, Uzbekistan: Uzbekistan Plant Protection Experimental Station, 16:1-425.

Parsons WT, 1973. Noxious Weeds of Victoria. Melbourne, Australia: Inkata Press Proprietary Ltd. 311 pp.

Parsons WT; Cuthbertson EG, 2000. Noxious Weeds of Australia, edition 2. Orange, New South Wales, Australia: NSW Agriculture.

Peck ME, 1961. A Manual of the Higher Plants of Oregon, edition 2. Portland, Oregon, USA: Oregon State University Press.

Pérez-García F, 1993. Effect of the origin of cypsela on germination of Onopordum acanthium L. (Asteraceae). Seed Science and Technology, 21:187-195.

Pettit WJ; Briese DT; Walker A, 1996. Aspects of thistle population dynamics with reference to Onopordum. Plant Protection Quarterly, 11(SUP2):232-235; 9 ref.

Piper G, 1984. Scotch thistle – a continuing menace in the Pacific Northwest. Pacific Northwest Weed Topics, 84:1-2.

Podlech D; Dieterle A, 1969. Chromosomenstudien an Afghanischen Pflanzen. Candollea, 24:185-243.

Polunin O; Stainton A, 1984. Flowers of the Himalaya. Delhi, India; Oxford University Press, 580pp.

Qaderi MM, 1998. Intraspecific variation in germination of Scotch thistle (Onopordum acanthium L.) cypselas. MSc thesis. University of Western Ontario, London, Canada.

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.

Raabe U, 1988. Flora and vegetation of villages in the northeastern Burgenland. Phytocoenologia, 16(2):225-258

Radford AE, 1986. Fundamentals of Plant Systematics. New York, USA: Harper and Row, Publishers.

Rechinger KH, 1979. Flora Iranica. Compositae III-Cynareae. Graz, Austria: Akademische Druck- u. Verlagsanstalt.

Scifres CJ; McCarty MK, 1969. Some factors affecting germination and seedling growth of Scotch thistle. Research Bulletin, Nebraska Agricultural Experiment Station, 228:1-29.

Sindel BM, 1991. A review of the ecology and control of thistles in Australia. Weed Research (Oxford), 31(4):189-201

Sindel BM, 1996. Overview of thistle management in Australia. Plant Protection Quarterly, 11(SUP2):285-289; 2 pp. of ref.

Sivinski R; Lowrey R; Peterson R, 1994. Additions to the native and adventive flora of New Mexico. Phytologia, 76:473-479.

Smith HA; Johnson WS; Shonkwiler JS; Swanson SR, 1999. The implications of variable or constant expansion rates in invasive weed infestations. Weed Science, 47(1):62-66; 34 ref.

Stewart WG; James LE, 1969. A guide to the flora of Elgin County Ontario. St. Thomas, Ontario, Canada: Catfish Creek Conservation Authority.

Steyermark JA, 1963. Flora of Missouri. Ames, Iowa, USA: The Iowa State University Press.

Szafer W, 1966. The Vegetation of Poland. Oxford, UK: Pergamon Press.

Taylor RJ, 1990. Northwest weeds. The ugly and beautiful villains of fields, gardens and roadsides. Missoula, USA; Mountain Press Publishing Co., vi + 177 pp.

Thomas AG, 1976. 1976 Weed survey of cultivated land in Saskatchewan. Regina, Canada: Agriculture Canada, 93 pp.

Toole EH; Brown E, 1946. Final results of the Duval buried seed experiment. Journal of Agricultural Research, 72:201-210.

USDA-NRCS, 2002. The PLANTS Database, Version 3.5. National Plant Data Center, Baton Rouge, USA. http://plants.usda.gov.

Vitou J; Briese DT; Sheppard AW; Thomann T, 2001. Comparative biology of two rosette crown-feeding flies of the genus Botanophila (Dipt., Anthomyiidae) with potential for biological control of their thistle hosts. Journal of Applied Entomology, 125(1/2):89-95; 12 ref.

Vorobiov MY, 1960. On certain biological features of biennial weeds of the Danube steppe. Ukrain Botanichnii Zhurnal, 17:43-49.

Watson AK, 1986. Morphological and biological parameters of the knapweed nematode, Subanuguina picridis. Journal of Nematology, 18:154-158.

Weber WA; Wittmann RC, 1996. Colorado Flora: Eastern Slope, edition 2. Niwot, Colorado, USA: University Press of Colorado.

Weinert E; Hellwig B, 1987. Distribution pattern of indicator species in the area of the Beber and Olbe valleys near Haldensleben. Hercynia, 24(4):437-451

Wheatley WM, 1981. Winning the thistle war. Agricultural Gazette of New South Wales, 92(2):25-28

Williams G, 1982. Elsevier’s Dictionary of Weeds of Western Europe. Amsterdam, The Netherlands: Elsevier Scientific Publishing Company.

Williams G; Hunyadi K, 1987. Dictionary of Weeds of Eastern Europe. Amsterdam, Netherlands: Elsevier.

Willis JH, 1972. A handbook to plants in Victoria. Carlton, Victoria, Australia: Melbourne University Press.

Young JA; Evans RA, 1969. Control and ecological studies of Scotch thistle. Weed Science, 17:60-63.

Young JA; Evans RA, 1972. Germination and persistence of achenes of Scotch thistle. Weed Science, 20(1):98-101

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

Ae Fond Kiss

Beautiful Eryngium Thistles, Exotic Vanda Orchids, Purple Veronica and Lizianthus make up this gorgeous hand-tied bouquet.

£34.99

Order Now

Uisge Beatha

Whiskey was a perfect name for this warm coloured bouquet. Sadly it does not have an ounce of whiskey in it but it sure is beautiful and fitting.

£29.99

Order Now

Heart’s in The Highlands

Spikey Eryngium Thistles purple Veronica and Lizianthus and lush foliage’s and of course some Tartan Ribbon make it our Highland Bouquet.

Order Now

Cranachan

Cranachan, The Scottish desert of the celebration of the harvest. These beautiful blooms certainly look good enough to eat!

£39.99

Order Now

Bonnie Basket

Loveliest selection of flowers hand delivered in a glass vase. A gorgeous floral gift perfect for any occasion.

Order Now

The Gathering

The Gathering of beautiful blooms in a zinc watering can. Rustic and fun! This beautiful arrangement is perfect for a ‘Get well soon’ as it needs little care.

Order Now

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

rate this answer

Not Yet Rated

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

QUESTION:

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.

ANSWER:

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.

More Plant Identification Questions

Plant identification
September 05, 2011 – This incredible plant has grown up in the past two months. Considering the extreme heat of this summer, my husband assumes it must be a weed. We have had this skinny strip of dirt for four years, and …
view the full question and answer

Plant identification site
May 17, 2010 – Is there a site I can use to identify plants by photos of leaves, flowers, berries etc? I found a plant in my yard I cannot identify. The nursery near us could not identify it. It has some groups/clus…
view the full question and answer

Plant identification for Louisiana
September 12, 2009 – Trying to identify a “fruit bearing” plant around Natchitoches, Louisiana. Grows about waist high to average man, slightly elongated green leaf, bearing small green “fruit” or “berry”, with pape…
view the full question and answer

Plant identification
October 20, 2010 – Need to identify multi branched plant, feathery appearance, approx 6′ tall stalks, grows in clusters. Tiny whitish/pink flowers at top of stems. Very similar in appearance to milfoil, only these grow…
view the full question and answer

Identification of plant with red berries toxic to dogs
August 29, 2011 – I recently retrieved my poor doggy from the Vet. He had eaten a berry from an invasive-commonly seen brushy plant growing along my neighbors fence line. We try to keep our side clear-but the small lar…
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.

Luontoportti

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

Follow us!

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.

Leave a Reply

Your email address will not be published. Required fields are marked *