Flowering weeds in Colorado are adapted to drier conditions, with the blue flowers of chicory standing out against the landscape. These plants often surprise newcomers who expect only grass and dirt. Instead, you will find a mix of colors, shapes, and survival strategies. Many of these weeds are actually edible or medicinal, though some can be invasive. Knowing what grows in your yard or along trails helps you manage them better. This guide covers the most common flowering weeds in Colorado, how to identify them, and what to do with them.
Flowering Weeds In Colorado
Colorado’s unique climate—low rainfall, high altitude, and intense sun—shapes which weeds thrive here. Many species have deep taproots or fuzzy leaves to conserve water. Others bloom quickly after rain. Let’s look at the most common ones you will encounter.
Common Yarrow (Achillea Millefolium)
Yarrow is a hardy perennial with flat clusters of white or pink flowers. Its feathery leaves smell like pine when crushed. You will find it in meadows, roadsides, and even your lawn. It blooms from June to September.
- Height: 1 to 3 feet
- Flower color: White, sometimes pale pink
- Leaf shape: Fern-like, finely divided
- Uses: Medicinal for wounds and colds; attracts pollinators
Yarrow is not invasive but spreads easily. If you want to remove it, pull the taproot before it seeds. Otherwise, let it grow for beneficial insects.
Spotted Knapweed (Centaurea Stoebe)
This is a problematic invasive weed. It has purple, thistle-like flowers with black-tipped bracts. The leaves are lobed and hairy. Spotted knapweed forms dense patches that crowd out native plants.
- Look for pink to purple flowers from July to October.
- Check the bracts under the flower head—they have black spots.
- Leaves are gray-green and deeply divided.
Control methods include pulling before seed set, mowing, or using herbicides. Do not compost the seed heads.
Musk Thistle (Carduus Nutans)
Musk thistle is a tall, spiny weed with large, nodding purple flower heads. It grows in pastures, along ditches, and in disturbed areas. Each plant can produce thousands of seeds.
- Height: 2 to 6 feet
- Flower: Solitary, drooping, up to 2 inches wide
- Stem: Winged with spines
- Blooms: May to August
Remove musk thistle by cutting the root below the soil line. Wear gloves. Biological controls like weevils can also help.
Curly Dock (Rumex Crispus)
Curly dock has tall flower stalks with greenish flowers that turn brown. Its leaves are long, wavy-edged, and edible when young. The taproot can go deep into the soil.
You will see it in lawns, gardens, and waste areas. The flowers are not showy but add texture. Harvest young leaves for salads or cook them like spinach. Older leaves are bitter.
Prickly Lettuce (Lactuca Serriola)
Also called wild lettuce, this weed has yellow dandelion-like flowers. It grows upright with prickly spines on the leaf midribs. The sap is milky and can be used as a mild sedative.
- Height: 2 to 5 feet
- Flowers: Yellow, opening in the morning
- Leaves: Lobed, with spines underneath
- Habitat: Roadsides, fields, gardens
Prickly lettuce is easy to pull when the soil is moist. It self-seeds heavily, so remove flower heads before they mature.
Field Bindweed (Convolvulus Arvensis)
Field bindweed is a creeping vine with white to pink trumpet-shaped flowers. It is also called morning glory. The roots can grow 10 feet deep, making it very hard to eliminate.
This weed wraps around other plants and chokes them. It blooms from June to September. To control it, repeatedly pull or dig out roots. Smothering with cardboard and mulch works over time.
Oxeye Daisy (Leucanthemum Vulgare)
Oxeye daisy looks like a large, white daisy with a yellow center. It is a common roadside weed in Colorado. It spreads by seeds and rhizomes.
- Height: 1 to 3 feet
- Flowers: White petals, yellow disk, 1-2 inches wide
- Leaves: Dark green, toothed, spoon-shaped
- Blooms: May to August
This plant is considered invasive in some areas. Pull it before it flowers to prevent spread. It can cause skin irritation in some people.
Canada Thistle (Cirsium Arvense)
Despite its name, Canada thistle is native to Europe. It has small, purple flower heads and creeping roots. It forms dense colonies that are hard to control.
- Flowers are smaller than musk thistle, about 1 inch wide.
- Leaves are spiny and lance-shaped.
- It spreads aggressively through root fragments.
Mowing before flowering can reduce seed production. Herbicides are often needed for large infestations. Do not till infested soil, as it spreads roots.
Dandelion (Taraxacum Officinale)
Dandelions are everywhere in Colorado. Their bright yellow flowers turn into puffballs. The leaves are edible and rich in vitamins. The taproot is deep and hard to remove fully.
- Flowers: Yellow, single on hollow stems
- Leaves: Toothed, forming a rosette
- Blooms: March to November
- Uses: Salad greens, tea, wine
To control dandelions, dig out the entire root. Or, simply enjoy them as a food source. They are not invasive but can be a nuisance in lawns.
Purple Loosestrife (Lythrum Salicaria)
This is a tall, showy weed with spikes of magenta flowers. It grows in wet areas like ditches and ponds. It is highly invasive and can overtake native wetlands.
In Colorado, it is less common than in other states but still a threat. Report sightings to local authorities. Do not plant it in gardens. Remove by hand or use approved herbicides.
Yellow Sweetclover (Melilotus Officinalis)
This weed has tall stalks with small, yellow, pea-like flowers. It smells like vanilla when dried. It grows in dry, disturbed soils.
- Height: 3 to 6 feet
- Flowers: Yellow, in elongated clusters
- Leaves: Three-part, clover-like
- Blooms: June to September
Sweetclover is a biennial. It fixes nitrogen in the soil but can become weedy. Mow before it seeds to control spread.
Houndstongue (Cynoglossum Officinale)
Houndstongue has reddish-purple flowers and rough, tongue-shaped leaves. The seeds have burrs that stick to animals and clothing. It is toxic to livestock.
This weed grows in pastures and open woods. Remove plants before they seed. Wear gloves as the hairs can irritate skin.
Cheatgrass (Bromus Tectorum)
Cheatgrass is a grassy weed with small, inconspicuous flowers. It turns red-brown in summer and dries out, creating fire hazards. It is highly invasive in Colorado.
While not a flowering weed in the traditional sense, its seed heads are noticeable. Control includes grazing, mowing, and prescribed burns. It is a serious problem in rangelands.
How To Identify Flowering Weeds In Colorado
Identifying weeds correctly is the first step to managing them. Use these tips:
- Look at the flower shape, color, and arrangement.
- Check leaf shape, edges, and arrangement on the stem.
- Note the plant height and growth habit (clumping, spreading, upright).
- Observe where it grows: sun or shade, wet or dry.
- Take a photo and compare with online resources like Colorado State University Extension.
Many weeds look similar. For example, musk thistle and Canada thistle are both purple but differ in size and root system. Practice makes perfect.
Common Look-Alikes
Some native plants resemble weeds. For instance, native blue flax looks like chicory but has smaller flowers. Learn the differences to avoid removing beneficial plants.
- Chicory vs. Blue Flax: Chicory has larger, more numerous flowers; flax has delicate, five-petaled blooms.
- Oxeye Daisy vs. Shasta Daisy: Oxeye is smaller and more weedy; Shasta is a garden plant with larger flowers.
Managing Flowering Weeds In Colorado
You have several options for control. Choose based on the weed type and your location.
Manual Removal
Pulling weeds by hand works for small areas. Do it after rain when soil is soft. Remove the entire root to prevent regrowth. For taprooted weeds like dandelion, use a weeding tool.
- Water the area the day before.
- Grasp the weed at the base.
- Pull slowly and steadily.
- Dispose of weeds in the trash, not compost.
Mowing And Cutting
Mowing prevents seed production but does not kill perennial weeds. Cut before flowers open. For thistles, cut at the base. Repeat every few weeks.
Herbicides
Use herbicides as a last resort. Choose products labeled for the specific weed. Apply on calm days to avoid drift. Follow label instructions exactly. Organic options like vinegar can work on young weeds.
Prevention
Healthy lawns and gardens resist weeds. Water deeply but infrequently. Mulch garden beds. Plant native species that compete well. Avoid disturbing soil unnecessarily.
Beneficial Uses Of Flowering Weeds
Not all weeds are bad. Many have uses:
- Edible: Dandelion, curly dock, purslane, lamb’s quarters
- Medicinal: Yarrow, prickly lettuce, plantain
- Pollinator support: Chicory, oxeye daisy, sweetclover
- Soil improvement: Sweetclover fixes nitrogen; dandelion breaks up compacted soil
Harvest weeds from areas free of pesticides. Wash thoroughly. Start with small amounts to test tolerance.
Edible Weed Recipes
Try these simple ideas:
- Dandelion greens sautéed with garlic
- Curly dock leaves in salads (young leaves only)
- Purslane stems in stir-fries
- Chicory root roasted as a coffee substitute
Invasive Weed Alert
Some flowering weeds in Colorado are classified as noxious. This means they must be controlled by law. Examples include:
- Spotted knapweed
- Musk thistle
- Canada thistle
- Purple loosestrife
- Houndstongue
Report large infestations to your county weed manager. Do not transport these plants. Clean boots and equipment after hiking.
Seasonal Guide To Flowering Weeds
Weeds bloom at different times. Knowing the season helps with identification and control.
Spring (March-May)
- Dandelion
- Prickly lettuce (early)
- Yellow sweetclover (late spring)
Summer (June-August)
- Chicory
- Oxeye daisy
- Spotted knapweed
- Musk thistle
- Field bindweed
Fall (September-November)
- Curly dock (seeds)
- Canada thistle (second flush)
- Houndstongue (seeds)
Frequently Asked Questions
Are flowering weeds in Colorado dangerous?
Some are toxic, like houndstongue to livestock. Others cause skin irritation. Learn to identify them before handling. Wear gloves when in doubt.
Can I eat flowering weeds in Colorado?
Yes, many are edible. Dandelion, curly dock, and purslane are safe. Avoid weeds near roads or sprayed areas. Start with small amounts.
How do I stop weeds from spreading?
Remove them before they seed. Mulch garden beds. Use ground covers. Keep your lawn healthy. Pull weeds when small.
What is the most common flowering weed in Colorado?
Dandelion is probably the most widespread. Chicory is also very common along roadsides. Both are easy to spot.
Should I use chemicals on flowering weeds?
Only as a last resort. Manual removal and prevention work well for most. Chemicals can harm beneficial insects and soil health. Use them sparingly.
Flowering weeds in Colorado are part of the landscape. Some are beautiful, some are troublesome. With the right knowledge, you can manage them effectively. Whether you choose to remove them or use them, understanding these plants helps you live in harmony with your environment. Keep an eye out for new species, as climate change may bring new weeds. Enjoy the colors, but stay informed.