Weed Control
Home ⟩ Noxious Weeds ⟩ Pink and Purple Flower Plants ⟩ Scotch Thistle
Scotch Thistle
Information | Images
Onopordum acanthium
Biennial
Identification and management tips
- Scotch thistle is an imposing 8 ft tall plant with purple spiny flowers and 2 ft long leaves covered in woolly hairs.
- Scotch thistle is best controlled in the rosette stage the 1st year, either mechanically or chemically.
- If an existing seed source is dormant in the soil, re-treatments will be necessary for 4-6 years and are most effective when followed with revegetation.
Most effective control methods and timing
| March | April | May | June | July | Aug | Sept | Oct |
|---|---|---|---|---|---|---|---|
|
Prev |
Prev Chem |
Prev Chem |
Mech |
Mech |
Mech |
Mech Chem |
Mech Chem |
Prevention (Prev)
Monitor and destroy new plants before seed production.
Mechanical (Mech)
Hand pulling, digging, cutting, mowing and tilling.
Cultural (Cult)
Biological control agents, livestock grazing, and revegetation practices.
Chemical (Chem)
Selective herbicides based on the plant and the specific location. Check our weed fact sheets for specific control information.
Links
Photo credits
Left to right: Washington State Noxious Weed Board