Thistle
Feature with prickles on leaves and stems, most thistles are undesirable (Canada, Musk, Scotch, Russian) are Some of them are noxious weeds in Utah.
Life cycle
They are either perennial or binnial.
Hazard
What damage does this invasive species cause?
Control
How to get rid of them?
Prevention
How to prevent those keep coming back?
Life cycle
They are either perennial or binnial
Control
How to get rid of them?
Hazard
What damage does this invasive species cause?
Prevention
How to prevent those keep coming back?
Life cycle
They can be biennial or perennial; can spread by extensive roots or purely by seeds depends on the variety. The stalks and roots are edible don’t let them go seeded as most of them are invasive.
Featured with spiky leaves, they have a very long tap root and make it hard to pull.
They can grow to 6-12′ tall depends on the varieties.
Scotch thistle flower (invasive).
Hazard
Canada, Scotch and Musk thistles are considered as noxious weeds in Utah. They adapted to a broad range of soils and spread aggressively.
Why are they considered as noxious weeds?
Musk thistle can produce up to 20,000 seeds per plant, only 1/3 being viable. Canada thistle form dense clones by roots. Breaking up the roots by plowing only increases the number of plants. (Pic: 2 years underground growth of Canada Thistle from original 1′ of root. Their roots can go 15′ wide and deep.)
Control
Easy to pull by hand before it goes seeded. If the seeds already go in the ground, consider a big scale of physical or chemical removal methods.
Digging, Hoeing
pull the roots- 100% effective
- No chemical involved. No other plants are harmed.
- Gloves are recommended if you choose to hand pull
- Tilling won’t work for Canda thistles since you’ll just get more root clumps
- You can compost it before it goes seeded.
Cultural control
competitive plants- Plant native perennials and mulch it heavily.
- Or maintain a healthy drought-resistant plant cover.
- Keep the soil healthy by fertilizing it and watering it regularly.
- You still need to get rid of the current thistles.
Chemical
postemergent broadleaf herbicide- Effective and easy for big infestation.
- Toxicity depends on the products you choose. Please read labels before you apply to avoid the harm.
- Herbicides might harm your plants around it, with potential health hazards if you don’t use it correctly.
- Do not spray when it is windy or raining, or when rain is forecast. Do not cut sprayed plants for at least 2 weeks after herbicide application.
Prevention
Timing of control is important to seed prevention. Eradicating existing infestations requires several years of controlling all germinating seedlings.
Mulch it heavily
This way can prevent the new seeds from rooting and sprouting. But it won’t cut the growth of Canada thistle since they spread from roots.
Remove it before it goes seeded
Since they can produce thousands of seeds, identify and remove the seedling before they go mature is important in prevention.
Plant native species
The most sustainable long-term way is having strong native perennials occupying the space to outcompete weeds.