Irene Shonle, CSU Extension Gilpin County. It is heartening to see so many people who are committed stewards of their land who are working to eradicate the noxious weeds on their property.  Thank you all!

It is possible to be a little too enthusiastic, though. This happens when someone pulls or treats the wrong plant – a plant that has the misfortune of looking like a noxious weed. These look-alike plants are often native, and can provide good habitat for pollinators, or at the very least, will occupy space that otherwise could be invaded by a noxious weed, so it’s best to learn how to distinguish which is which.

Some of the most common mistaken identities up here are Golden banner/yellow toadflax, pineapple weed/scentless chamomile, cutleaf daisy/oxeye daisy and fireweed/purple loosestrife.

Golden banner is a native plant – it blooms in the spring, and has solid yellow flowers, and three-lobed (trifoliate) leaves. Yellow toadflax blooms in the second half of summer with two-tone yellow flowers with a darker throat, and has strap-shaped leaves.

Pineapple weed, while an introduced plant, is not on the noxious weed list. It is, however, having a very good year, and can be easily controlled by hoeing or pulling.  It has ferny leaves that, when crushed, smell like pineapple. The whole plant only gets to 6-8” tall at the most. It develops small yellow buttons, but never white ‘petals’ (ray flowers). Scentless chamomile also has ferny leaves, but they have no odor (the plant names give good ID clues). It gets up to 3’ tall, and has hundreds of white flowers. 

Cutleaf daisy is a native plant with small white flowers and finely cut leaves that could look a little ferny. It can (and has been) mistaken for pineapple weed, scentless chamomile and oxeye daisy. The flowers on the native bloom in the spring, and the foliage has no smell. The whole plant is no taller than about 4” tall. Oxeye daisy blooms mid-summer, and has much larger flowers, as well as broader leaves with teeth (not ferny). The plant grows 1’-3’ tall.

Fireweed is a native plant with 4 pink petals. It blooms mid-summer to fall. The leaves are alternate, and the plant can grow up to 4’ tall. Purple loosestrife is not known to be up at this elevation, but people have frequently pulled out fireweed by mistake. Loosestrife has opposite leaves (or even whorled – meaning that four leaves come out of the stalk at the same place). It has 5-7 purple petals and can grow up to 8’ tall.  

Finally, we have many wonderful native thistles, and it’s easier to just learn to recognize our two common noxious thistles, Canada thistle and musk thistle, rather than all of the native thistles. Musk thistle has large, solitary purple flowers with a formidable row of teeth under the flower. The leaves have a whitish edge. Canada thistle usually forms thickets due to the root system, and has clusters of small purple flowers. 

When in doubt, feel free to email a clear picture showing flowers and leaves to the Gilpin Extension office (Irene.shonle@colostate.edu) or bring in a sample. It’s a wonderful thing to control noxious weeds, just make sure you know which plants to pull!  For more information and pictures, we have a brochure online: https://gilpin.extension.colostate.edu/wp-content/uploads/sites/29/2016/09/Noxious-weed-look-alikes.pdf.

The CSU Gilpin County Extension Office is located at the Exhibit Barn, 230 Norton Drive, Black Hawk, CO 80422, 303-582-9106, www.gilpin.extension.colostate.edu. Colorado State University Extension provides unbiased, research-based information about, horticulture, natural resources, and 4-H youth development. Colorado State University Extension is dedicated to serving all people on an equal and nondiscriminatory basis. 

Originally published in the July 11, 2019, print edition of The Mountain-Ear. You can buy a low resolution, downloadable pdf of this paper at https://themtnear.com/product/2019-07-11/