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Steamboat Magazine

Weed It Out: 10 Weeds to Look Out For

05/08/2024 03:12PM ● By Elainna Hemming
(Photo: Meadow Knapweed, A relative to the diffuse knapweed)

Steamboat Springs, CO -
Spring gardening doesn’t always entail vibrant petals and sweet scents; sometimes dangerous plants need to be plucked to keep a garden both beautiful and healthy. It’s critical to understand the characteristics of toxic weeds and their proper control method in order to protect everyone’s home greenery. According to Routt County, here’s 10 noxious weeds that gardeners should keep an eye on. 

These first five weeds are on Routt County’s high priority list - meaning the county’s ultimate goal is complete eradication of the species in the area. The first method of control should be complete removal of the weed.

1) Diffuse Knapweed: Scientifically known as centaurea diffusa, this biennial weed has yellow-spined floral bracts with comb-like teeth and white or lavender flowers. Ensure the root is severed thoroughly below the surface to remove it. 

2) Meadow Knapweed: A relative to the diffuse knapweed, the meadow species has long, straight stems with vibrant green leaves and pink or purple flowers. Eradication is Routt County’s final goal; remove it by hand, pulling up small groups at a time and destroying the entire root system. Meadow knapweed is resilient, so the removal site should be closely monitored for resurgences. 

3) Orange Hawkweed: As the name suggests, this weed tends to be easily identifiable by its deep, red-orange flowers, as well as its hairy leaves and stems. It’s extremely difficult to remove, but it should be closely monitored. 

4) Scotch Thistle: A tall plant (mature ones grow up to 12 feet), Scotch thistles have large, hairy alternating leaves and purple flower clusters at the top. Similar to the diffuse knapweed, simply cut the root underneath the dirt. 

5) Whitetop/Hoary Cress: White flowered and with erect stems, the hoary cress, or whitetop, only reaches about two feet tall and appears a bluish green. Mowing over the plant repeatedly is the most efficient method of removal as it stresses the plant and makes it more susceptible to herbicide treatment. 

The next five weeds, while still harmful, only need to be properly contained – so don’t worry if you can’t remove them entirely. 

6) Houndstongue: Houndstongue’s seeds have a velcro-like texture with small magenta flowers along the stems. To remove, cut or pull the weed along with its root while it is still young, then clean up the thick debris layer left behind. If debris is left in the soil, it could hinder a successful germination of other flowers and plants.

7) Dalmatian Toadflax: Often confused with snapdragons, the dalmatian toadflax bears yellow flowers and waxy heart-shaped leaves. This three foot tall weed needs to be methodically hand-pulled, as the roots can extend as far into the soil as its own height. 

8) Leafy Spurge: These plants have a skinny stem and yellow green flowers covered in a milky latex. Mowing every 2 to 4 weeks will drastically reduce seed production.

9) Oxeye Daisy: Although this weed may look like an innocent daisy, it’s still toxic to the environment. It grows in clusters with dark, skinny stems and small leaves. These plants need to be hand pulled when the soil is damp for easiest removal.

10) Bull Thistle: With similar coloring to the Scotch thistle, the bull thistle is smaller and its flowers have a wide, prickly bulbous base. This thistle’s root must also be severed below the surface.