Weeds can be a nuisance in lawns, but those with blue flowers can be particularly frustrating. Not only do they mingle with the aesthetics of your lawn, but they also seem difficult to distinguish from regular houseplants.

This article discusses weeds with blue flowers in lawns, their characteristics, and how you can control them. 

Weeds With Blue Or Purple Flowers Found On Lawns

Some of these plants could surprise you as you may not have considered them a weed until now.

1. Germander Speedwell (Veronica chamaedrys) 

Germander-SpeedwellGermander Speedwell is a common weed you’ll find in lawns and gardens. The weed was initially grown as a rock plant until gardeners discovered its invasive nature. 

German Speedwell is a low-growing weed with small, bright, delicate blue-purple flowers. The flowers have a short life span lasting about 24 hours, after which they drop to the ground. 

The leaves are typically arranged opposite each other on the stem. German Speedwell can be challenging to control because of its ability to spread and choke other plants in the area. It forms a dense weed carpet. 

You may accidentally spread this weed around your lawn when composting. This could happen during general pruning when you mix and add all the plant debris to your compost pit.

If the compost isn’t well decomposed, you will spread speedwell across your property, causing them to take root and grow again. 

How To Control

  • Mow your lawn to scatter the stem sections and prevent the weed from flowering and producing seeds. 
  • Hand-pull the entire root system from the ground to prevent regrowth.   
  • Keep your lawn or grass healthy by boosting grass growth with appropriate feeds in the spring and summer months and regular watering
  • Avoid the application of weed killers on newly established lawns in less than six months. Consider the application of selective herbicides to eliminate broadleaf weeds such as 2,4-D. 

2. Creeping Charlie (Glechoma hederacea)

Glechoma-hederaceaAlso known as ground ivy, Creeping Charlie is a typical perennial weed in lawns, gardens, and areas with moist soils.

It gets ladened with funnel-shaped purple-blue flowers and round, toothed leaves in spring. The leaves are positioned opposite each other on square creeping stems that grow 4-8 inches tall.

Creeping Charlie spreads by seeds and stolons that stretch along the ground. Noticeably, its stems produce a solid minty odor when crushed.

The blue-flowered weed spreads quickly, forming dense mats that choke other plants. The weed is often confused with the annual winter henbit.

The plant is a persistent weed and regrows from stem clippings or roots left in the soil. 

How To Control

  • Keep your lawn sunny since Creeping Charlie loves moist and shady places.
  • Prune trees around your lawn, water your lawn less frequently, or improve drainage. 
  • Control the weed with herbicides such as dicamba, triclopyr, and 2, 4-D. We recommend applying the herbicide when the plant grows in spring or fall. Remember to follow the instructions on the label. 
  • Handpull the weed in case of a small infestation. You should do this when the soil is moist to remove the entire root system. 

3. Chicory (Cichorium intybus)

Cichorium-intybusChicory is a herbaceous perennial native to Europe, Western Asia, and Central Russia. The weed has other common names such as coffee weed, blue sailors, or succory.

Chicory has pretty blue flowers that bloom from July to October. Its leaves are variable and deeply lobed— the lobes point away from the rosette.

Chicory flowers are sometimes pink or white and grow 1.5 inches wide with 5-sharp teeth at the blunt apex. 

The taproot is large, brown, and fleshy with milky sap and grows up to 30 cm long. Chicory grows quite tall, and this taints the image of your lawn.

The plant won’t typically invade undisturbed natural habitats but will easily invade poorly maintained lawns and disturbed areas. 

How To Control

  • Mow your lawn regularly to prevent the weed from flowering and producing seeds. 
  • Uproot the entire plant after wetting the seed bed and dispose of the weed properly to prevent reseeding. 
  • Maintain a thick, healthy lawn through regular fertilization or irrigation to prevent its establishment. 
  • Apply selective herbicide or spot-treat it with an MSM turf herbicide. 

4. Blue-Eyed grass (Sisyrinchium)

SisyrinchiumBlue-eyed grass falls under the genus Sisyrinchium, a native to North or South America. This weed blossoms in spring or summer, forming small flowers on long spikes. 

The flowers produced are pale blue, white, or deep violet. The North American species have more blue flowers compared to the South. 

The blue and purple flowers have yellow centers. Its leaves are narrow and grass-like. 

Blue-eyed grass can self-seed— typical of weeds from its origin. However, it won’t spread fast and invade like other weeds.

The weed forms tall clumps that will make your lawn ugly and unsightly. 

How To Control

  • Proper lawn care through mowing, watering, and fertilization. 
  • Use a herbicide in case of a large infestation, potentially the one labeled or manufactured to eliminate Blue-eyed weed. You can use a pre-or post-emergent weed eliminator, depending on the growth.  
  • Hand-pull the entire root system in case of a small infestation. 

5. Forget-Me-Not (Myosotis)

MyosotisForget-me-not is a herbaceous perennial weed that produces attractive blue, pink, and white flowers. The plant typically grows to a height of 4-12 inches tall. 

Its five-petalled flowers grow on single central stems with additional blooms on branching stems.

Forget-me-nots thrive in both sunny and shady locations, depending on the region. They prefer a shade in warmer southern climates.

The weeds readily self-seed and spread fast across the garden. They are considered invasive in several states. 

How To Control

  • Physically get rid of Forget-me-nots by uprooting them.
  • Smother the weeds with a thick layer of mulch.
  • Improve the health of your lawn to make it less susceptible to weed infestation. 
  • Eliminate them using post-emergent herbicides or other selective herbicides for use on lawns. 

6. Cornflower (Centaurea cyanus)

Centaurea-cyanusThe cornflower plant is known by several other names— Bachelor’s Button, Bluebottle, and strawflower. It’s native to Europe and a common weed in fields and along roads.

It grows well in cooler climates. The plant produces daisy-like flower heads measuring 1.5 inches in shades of lavender, white, blue, white, and maroon. 

The vibrant flowers emerge atop their lance-shaped green leaves beginning late spring into late summer. 

They have a distinctive cone-shaped center surrounded by pointed petals. 

Cornflowers prefer full sun to light shade with well-drained soils. This blue-flowered weed is generally considered non-invasive but can be problematic for other plants in your garden and different agricultural settings.

It attracts aphids and mealybugs that cause damage to other plants. 

How To Control

  • Practice dead-heading to control reseeding and natural spread. 
  • Hand-pull the entire plant, including the root system, from your lawn. 
  • Mow the lawn frequently to prevent the plant from growing tall. 
  • Use selective herbicides such as 2.4-D and dicamba to eliminate the plant without harming the surroundings.  

7. Wild violet (Viola odorata)

Viola-odorataSweet violet is a low-growing perennial native to Europe and Asia. You’ll typically find the plant in lawns and gardens.

Its heart-shaped leaves are hairy and deep green. Wild violets produce small blue-violet flowers with five oval petals. The flowers have a distinct fragrance. 

The flowers bloom in early spring but die off when the temperatures rise— leaving only the leaves. 

You shouldn’t confuse this weed with common wild dog violet, which is similar in appearance. 

Wild violet can grow up to 6 inches tall, spreading to form a dense ground cover. The weed can be difficult to control because it can spread quickly and colonize your lawn. 

How To Control 

  • Mow your lawn regularly to weaken and control wild violets. 
  • Smother the wild violets with a layer of mulch or use a vinegar solution to eliminate them. 
  • Use appropriate herbicides.
  • Hand-pull, in case of a small infestation. 

8. Creeping Bellflower (Campanula rapunculoides)

Campanula-rapunculoidesCreeping bellflower produces delicate and beautiful wildflowers on hairy, bright green foliage in the summer months. The naming can be attributed to its flowers, which are shaped like a bell with five petals fused at the base. 

The blue-violet flowers hang singly in clusters on slender stems that can grow up to 45cm tall. The plants thrive in full sun or partial shade in warmer climates and prefer well-draining soils.

Creeping bellflowers are invasive and can spread rapidly in given areas outcompeting native species. They produce up to 15000 seeds and multiply rapidly using underground rhizomes.

How To Control

  • Regularly mow your lawn to prevent the weed from flowering and seeding. 
  • Maintain your lawn to improve its overall health by regularly fertilizing, watering, and aerating. This enables your yard to compete with invasive weeds. 
  • Apply selective herbicides that target broadleaf weeds. Follow the manufacturer’s instructions on the label. 
  • Overseed your lawn with grass species that are more competitive than creeping bellflowers. 

9. Blueweed (Echium vulgare)

Echium-vulgareAlso referred to as viper’s bugloss, Blue devil, Blue thistle, Snake flower, and Cat’s tail, Blueweed is a short-lived perennial that grows up to 36 inches tall. 

The weed is native to Southern Europe and packs bell-shaped purple-blue flowers that protrude beautiful red stamens.

The funnel-shaped flowers, which grow in clusters at the top of the stem, bloom from late spring to early fall. The flowers may also be pink, purple, or rarely white.

Blueweed re-seeds rapidly, making it a moderately fast-growing weed. The plant loves full sun to partial shade with average to medium moist, well-draining soils.

As a typical weed, it is drought-tolerant and deer resistant.

Blueweed contains alkaloids that are toxic to livestock and humans if ingested in large quantities. Their rough hairs also cause dermatitis resulting in inflammation and irritation in humans.

With its ability to spread quickly, the plant spreads quickly and competes with other native species. 

How To Control

  • For small isolated infestations, dig the weeds out after making the soil moist. Ensure to dispose of them properly to prevent them from re-establishing. 
  • Prevent spread by maintaining hygiene in your garden. Clean footwear, vehicles, pets, and clothing after visiting infested areas.
  • Spot spray with herbicides containing glyphosate as the active ingredient. 

10. Meadow cranesbill (Geranium pratense)

Geranium-pratenseMeadow cranesbill is a clump-forming perennial native to Europe and Asia. The plant produces many large saucer-shaped blue-violet flowers that bloom from late spring to mid-summer. 

It is characterized by deeply lobed leaves with long pointed teeth growing up to 2- 3 ft tall. The plants prefer full sun or partial shade and well-draining soils. 

Although Meadow cranesbill is not considered invasive, it can attract other pests and disease vectors such as geranium sawflies, capsid bugs, and powdery mildew. 

It also has a deep tap root system that may make it difficult to control. 

How To Control

  • Apply a layer of organic mulch around your lawn to suppress its growth. 
  • Hand-pull or dig out small infestations. Remove the entire root system and dispose of it properly to prevent it from re-establishing.
  • Use mild herbicides.

Lesser-Known Blue-Flowered Weeds

These weeds are not that common. Some may not be invasive.

11. Blue Toadflax (Linaria canadensis) 

Linaria-canadensisBlue toadflax has other common names, such as Canadian toadflax and Blue toadflax. It’s an annual herb that produces blue-purple flowers. 

The blooms may also range from white and pink and appear in spring, summer, and fall. The leaves are linear to oblong-shaped, growing on tall and slender stems. 

The plant is native to North America and grows in fields along roadsides. It propagates through seeds and prefers full sun to light shade.  

The self-seeding plant can spread quickly, easily colonizing other plants in your lawn. Some parts of the plant are poisonous if ingested in large quantities. 

How To Control 

  • Pull the weed out by hand along with the root system and dispose of it properly. 
  • Apply herbicides with the active ingredient triclopyr or 2.4-D and follow the manufacturer’s instructions carefully. Make the application when the plant is actively growing. 
  • Regularly mow your lawn to prevent the spread of the weed through flowers and seeds. 
  • Apply a pre-emergent herbicide to prevent the germination of Bluetoad flax seeds. 

12. Common Blue Violet (Viola sororia) 

Viola-sororiaCommon blue violet has several other names, such as woody blue violet, Florida violet, Viola floridana, and others. The weed is native to Eastern and North America, and it’s popularly known for its attractive blue-violet flowers that pack conspicuous white throats.

It’s a low-growing perennial with heart-shaped leaves that have a glossy appearance and are serrated at the margins. The leaves are soft at the top but hairy on the underside. 

Common blue violet is a freely self-seeding weed that quickly grows 6 to 10 inches tall. It tends to colonize home gardens— denying your principal plants essential nutrients and sunlight.

Some people might be allergic to the plant’s pollen resulting in respiratory problems and skin irritation. The plant is also a pest attractant, attracting spider mites, snails, slugs, and the powdery mildew disease. 

How To Control

  • Regularly mow your lawn to keep the grass at an appropriate height and prevent common blue violet from taking over. 
  • Use selective herbicides that target common blue violet. Follow label instructions. 
  • Hand-pull small patches of the weed from your lawn. 

13. Siberian Squill (Scilla siberica) 

Scilla-sibericaSiberian squill is a bulbous perennial weed in the Asparagacee family. It’s native to Southwestern Russia and Turkey.

The plant grows up to 15cm tall, producing basal leaves that are narrow and strap-shaped. It produces intense blue bell-shaped flowers in early spring that occasionally range from white and pink.

Siberian squill thrives in average medium to well-draining soil with full sun or partial shade. It’s considered an invasive species that spreads and dominates the native plant communities. 

The plant parts, such as the leaves, bulbs, blooms, and seeds, are toxic to pests and livestock if ingested. 

How To Control

  • Dig and take them out by the roots. 
  • Use mulch-like cardboard or black plastic layers to cut out its active growing elements. 
  • Mow your lawn well before the weeds bloom to eliminate seed heads.

14. Asiatic Dayflower (Commelina communis)

Commelina-communisNative to South Asia, the Asiatic Dayflower is an annual weed that has since spread to many other parts of the world, including North America. The weed is a strikingly vibrant creeper characterized by bilaterally symmetrical bright blue flowers that bloom from June to September. 

Their long and fleshy leaves are densely arranged alternately along the stem measuring 8-13 cm long. The plant can stand upright or sprawl across the ground once it matures. 

Asiatic dayflower produces through seeds and can form roots at the leaf nodes in the presence of enough moisture. The weed spreads rapidly, quickly taking over an area. 

How To Control 

  • Hand-pull and destroy. 
  • Use mulch to suppress the growth of the weed. 
  • Eliminate the weed using a glyphosate herbicide in the event of a large infestation. However, some gardeners consider a flumioxazin pesticide to be more effective. Remember to follow the instructions on the label. 
  • Maintain proper hygiene in your garden to avoid re-introducing the plant to new areas. 
  • Maintain a healthy turf or ground cover to prevent re-establishment. 

15. Creeping speedwell (Veronica filiformis)

Veronica-filiformisCreeping Speedwell is a low-growing weed native to Eastern Europe and Western Asia. It has other common names such as Slender Speedwell, Birdseye Speedwell, creeping veronica, threadstalk speedwell, and many more. 

The plant grows and spreads by stolons and displays its blue-violet flowers during spring or early summer. The stolons or creeping stems form a dense mat-like ground cover. 

You will commonly find the weed in lawns, gardens, and other areas with well-drained and moist soil. Creeping Speedwell tolerates most turf herbicides— it can even survive applications of triclopyr and picloram.

The plant spreads rapidly, outcompeting other plants and disrupting the balance of a garden or lawn. Its ability to spread fast also makes it difficult to control. 

How To Control 

  • Pull stem bunches by hand.
  • Encourage vigorous grass growth on your lawn to out-compete the weed. 
  • Control the weed by applying a mecoprop/ioxynil mixture in spring or autumn and later redo the application after six months to eliminate regrowth.

16. Tiny Bluets (Houstonia pusilla) 

Housonina-pusillaTiny Bluet is an annual mat-forming winter wildflower in the family Rubiceae. The flower is native to North America and grows in various habitats, including fields, meadows, lawns, cemeteries, and woodland edges. 

The weed usually blossoms in early spring. Tiny bluets have a minute body structure— they grow 4-6+ inches tall with little four-petalled blue to violet blooms.

Their leaves are small, narrow, and arranged in opposite pairs along the stem. Tiny bluets can be invasive in some areas where they compete with native plant species for resources.

How To Control

  • Pull out the weeds in early spring before seed production. 
  • Use a pre-emergent herbicide in early spring to prevent the weed from establishing itself.
  • Eliminate existing tiny bluets with a post-emergent herbicide. 

17. Blue vervain (Verbena hastata)

Verbena-hastataBlue vervain is a native wildflower and a perennial herbaceous plant in the family Verbanaceae. The plant is native to Eastern North America, growing in wet meadows, stream banks, and damp river bottomlands. 

The plant has densely packed, purplish-blue flowers that bloom from July to September. Their leaves are lance-shaped and toothed, growing up to six feet tall on a square stem with opposite leaves. 

Blue vervain loves medium to wet soils under full sun. The plant self-seeds and spreads through rhizomes. Due to its ability to spread quickly, it is considered borderline invasive— it isn’t a typical weed.

The plant isn’t prone to pests and diseases but can be infested by powdery mildew under humid conditions.

How To Control

  • Hand-pull the plants in case of a light infestation. 
  • Mow your lawn regularly.
  • Use herbicides with 2,4-D, dicamba, and triclopyr as the active ingredient to control its growth.

18. Henbit (Lamium amplexicaule) 

Lamium-amplexicauleHenbit is the eighteenth entrant on our list of weeds with purple flowers. It’s a winter annual with greenish-purple square stems in the mint family. The leaves are egg-shaped and serrated with a deep green shade. 

Henbit is characterized by purple flowers arranged in whorls around the stem. Up to 200 seeds are produced from a single plant which makes it multiply rapidly and compete with desirable plants for nutrients, water, and sunlight. 

How To Control

  • Dig or pull out the entire root system.
  • Apply appropriate herbicides. 

19. Shamrock Pea (Blue Oxalis)

 

Shamrock Pea is a herbaceous hardy perennial plant in the family Oxalidaceae. It’s native to Africa and Asia, typically growing in mountainous regions. 

It has attractive clover-like leaves with five-petaled blue blooms similar to inverted hearts. The plant grows to about 4-8 inches tall and spreads through underground rhizomes. 

Shamrock grows well in areas with partial shade to full sun with moist, well-draining soils. This weed contains oxalic acid that is toxic to humans and livestock if ingested in large quantities. The plant can also colonize an area due to its fast-spreading nature.

How To Control

  • Pull out the whole root system from the ground early in time. 
  • Smother it with mulch, straw, or paper.
  • Eliminate it with a glyphosate herbicide.

20. Carpetweed (Ajuga reptans) 

Ajuga-reptansCarpetweed is an evergreen perennial in the family Lamiaceae. It grows to a height of 1 ft and is commonly found in gardens, lawns, and other disturbed areas. 

The weed has oval-shaped leaves with scalloped edges and produces small purple-blue flowers on terminal spikes. 

Carpetweed spreads quickly through numerous seeds, making it difficult to control. It typically forms a dense mat surrounding planting beds and lawns. 

How To Control 

  • Dig up runners and shallow roots twice a year. 
  • Apply an appropriate herbicide containing glyphosate or triclopyr to prevent regrowth. 

Wrap Up

While weeds with blue flowers may look appealing, it’s important to remember that they can quickly take over your lawn or garden and harm the native plant species.

By regularly removing these weeds, using the suggested methods, you can maintain a healthy and thriving green paradise on your property.

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