Thistle: creeping

Creeping thistle can quickly spread in grassland areas and borders. Once established, it can be difficult to eradicate permanently. You may find that repeated digging out of roots reduces the problem, but chemical control will provide a quicker solution.

Creeping thistle

Quick facts

Common name Creeping thistle
Botanical name Cirsium arvense
Areas affected Especially grassland and uncultivated soil
Main causes Thistles spread via creeping roots and air-borne seeds
Timing Seen and treated from spring to autumn

What is creeping thistle?

Creeping thistle (Cirsium arvense) is a weed that spreads using lateral roots. These roots are brittle and readily reshoot if broken. They should be controlled if you wish to grow garden plants in the area, since they compete for light, water and food.

Appearance

Spreading roots mean that the thistles form large clumps of spiny leaves and flowering stems ranging from 30cm-1m (1ft-3¼ft) in height on mainly grassland.

Dark pinky-purple flowers typical of the thistle family are borne July to September.

The problem

Creeping thistle (Cirsium arvense) is such a problematic weed because;

  • It produces a tap root on germination followed by lateral roots that grow horizontally. These lateral roots are brittle and produce buds at intervals that develop shoots
  • It easily regenerates from broken pieces. Individual plants, can form large clumps, are dioecious (either male or female) being virtually self-sterile. However, male and female plants growing adjacent to each other will cross-pollinate and a seed crop will be produced
  • Its seeds germinate readily, but particularly during periods of fluctuating temperatures, or when temperatures reach 20-30ºC (68-86ºF) during the day

Control

The best time to apply weedkillers to thistles is when they are growing vigorously, but have not yet flowered. Digging up the plants can be done at any time of year. They can be controlled using non-chemical or chemical methods.

Non-chemical control

Cultural control methods are not easy but can work if consistently applied;

  • Digging up creeping thistles is problematic because the roots will easily regenerate from broken pieces. Persistence will be needed
  • Weaken creeping thistle by repeatedly cutting down the top growth over a number of years. This is best done just before the flower heads show colour as much of the weed's food reserves will have been used up in flower production
  • Clearing by digging may take two or three seasons as the plants will easily regenerate from small fragments that have been overlooked

Chemical control

In grass;

  • Apply a selective lawn weedkiller containing clopyralid (Scotts Weedol Lawn Weedkiller or Vitax LawnClear 2). Several applications may be necessary to gain control
  • In rough grass areas, apply Vitax SBK Brushwood Killer, a selective herbicide based on triclopyr

In borders and unplanted areas;

  • Apply a systemic weedkiller containing glyphosate (e.g. Scotts Roundup, Bayer Garden Rootkill Weedkiller or Doff Glyphosate Weedkiller; or for spot treatment use Scotts Roundup Gel) just before the flower heads show colour
  • Spray the foliage thoroughly, which should turn yellow after about a week
  • Watch for any signs of regrowth the following year. You may find that two or three treatments are needed
  • Glyphosate is not selective and any nearby plants or grass coming into contact with the spray may be killed
  • Ensure you follow the directions on the packaging of weedkillers

Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Download

Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1a, 1b and 4)

Links

Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers
Weeds: non-chemical control

Advertise here

Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Discuss this

for the site or to share your experiences on this topic and seek advice from our community of gardeners.

  • Burnt House

    By Burnt House on 25/08/2015

    I have just bought a house with about two acres of ground with about 1 acre turned over to meadow. It would appear that the major flower is thistle. Is there any way of clearing about an acre of thistle without destroying the rest of the meadow? I am happy to mow but wonder whether this means that I can say goodbye to a wild flower meadow for the next few years until the thistle is under control.