What's that PNW Weed: Invasive Catsear Flower
- Katie Burnham
- Aug 10, 2024
- 3 min read
No, it's not a dandelion! Catsear (Hypochaeris radicata), also commonly known as false dandelion, spotted catsear, and hairy cat's ear, is an invasive herbaceous perennial weed in Washington State and throughout the Pacific Northwest. It's native to Europe, Western Asia, and Northern Africa. Invasive catsear flower is toxic to livestock and was listed as an invasive species in Washington back in 1988.
General Description of Catsear
Catsear is commonly mistaken for dandelion because both plants have ubiquitous little yellow flowers that grow en masse everywhere! And I can relate to this--as I type this outside in the shade, I can count about 5 million catsear growing in my yard! (And I would think they were dandelions if I hadn't done my weed research).
Catsear flowers are yellow with petals about 1/4 to 3/4 in length with green bracts at the base. Flowerheads are "dandelion-like" forming a circular shape at the end of a long, upright stem. Stems ooze a milky white juice when broken in half. Dandelions, on the other hand, have hollow stems that do not produce milky juices.
Catsear leaves are a limy green and very fuzzy. The tiny fuzzy hairs are white and located on both the top and bottom of the leaf. In contrast, dandelion leaves are smooth and hairless. Leaves can vary in length between 1-13 inches and form a spiral around the flower stem.
When catsear is finished flowering, the plant switches to seed dispersal. The seeds are wind-dispersed and have white, hairy bristles (pappus). In addition to reproducing by seed, catsear also reproduces with crown and root sections.
Why Catsear is an Invasive Weed
Catsear seems to grow anywhere, with a limited amount of nutrients and water and outcompetes natives (and even grass). Invasive plants, in general, reproduce prolifically and outcompete native plants, whereby entire ecological systems may be altered. While I've never seen a whole ecosystem completely changed by catsear, I have noticed their abundance and think they're a nuisance. As a purely anecdotal observation, I do see bees, wasps, and other insects visiting catsear, so the pollen may serve as a food source during dry summer months when few other plants are flowering.
Catsear grows in disturbed soils, roadsides, fields, lawns, garden beds, and waste areas--so just about anywhere in Washington.
How to Manage Catsear
In my professional (and personal) experience, I have lost the battle to catsear (I know, I can't believe I'm admitting this, but it's the truth). In July and August when catsear are blooming, I still mow the lawn to remove the flowers and prevent seeds from forming and dispersing. However, I do not make a point to remove each catsear plant from my lawn (this would take approximately a million hours that I don't have).
If you're the type of person that needs a pristine lawn, the only true method of management is to mechanically remove the entire plant (including the taproot and leaves). Using a dandelion extraction tool is the best method, but a spade or hoe will also work. Make sure to remove ALL parts of the plant, as catsear can regrow from root and crown segments. When I remove catsear from my garden, I like using my Japanese hand hoe to get under the leaves and pop out the entire plant (root intact).
If you find yourself battling catsear in pathways and gravel driveways, try spraying with horticultural vinegar on a sunny day. The vinegar will burn the plant and cause it to shrivel up and die. I do not recommend spraying catsear in lawns or gardens, as the vinegar will kill any plant sprayed.
Recap
Catsear (Hypochaeris radicata) is an invasive perennial weed commonly found growing anywhere on roadsides, pastures, lawns gardens, and even cracks in the sidewalk) in Washington State and the greater Pacific Northwest. It has dandelion-like yellow flowers and hairy lime-green leaves. The only way to remove dandelions is to mechanically extract the entire plant. However, catsear are so prolific, that mechanical removal may not be rational. Prevent seed head formation and dispersal by mowing weekly (even after the grass stops growing).
Sources
Washington State Noxious Weed Control Board
Penn State Extension
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