- Invasive Species Management
- Current Topics
Noxious Weed Treatments
Perennial Noxious Weeds
Shallow fibrous rooted species
- Oxeye daisy
Shallow fibrous rooted plants may be removed. Pull the plant or cut the seedheads, place them into a plastic bag, secure the top of the bag, and place the bag into the trash. If the plant has no buds, it can be left on the ground but if it has any buds, it needs to be bagged and put into the trash too.
Species with spreading roots
- Canada thistle
- Dalmatian and Yellow toadflax
- Leafy spurge
Species that spread by rhizomes and spreading roots should not be pulled. They can be clipped and any plants with flower buds will need to be bagged and put into the trash. Plants without buds can be mowed. This won't control the plants but will make them more susceptible to fall herbicide applications.
Time spring herbicide treatments to before flowering to early flowering. Fall treatments should be timed to later in the season as the plants are moving resources to their roots.
Good results using Milestone on Canada thistle in late summer has also been reported.
Always refer to the herbicide label for specific instructions.
Species that spread by fragments
- Purple loosestrife
Poison hemlock (Conium maculatum) is a very common plant in North America. In Colorado, it is a List C weed which means it is recommended for control but is not required to be controlled. Due to the increased moisture, populations are higher than normal this year.
If you have it on your property, it is best to control it when it is small. Cutting or removing before it flowers in early summer works well but may need to be repeated. If you are dealing with it once it flowers, you should clip and bag the flowers and dispose of them in the trash. Be sure to wear gloves, long sleeves, and eye protection when handling.
Treating with herbicide at the rosette stage will control it. Visit our Jeffco ISM Poison Hemlock Information page for more information.
University of California IPM - Poison Hemlock
Purdue Extension Poison Hemlock Fact Sheet (PDF)