Weed with Tiny Blue Flowers: A Complete Identification Guide

Tiny blue flowers blooming in your lawn or garden can be a beautiful sight. But for many homeowners, these delicate flowers represent weedy invaders that need to be controlled. If you spot unfamiliar weeds with tiny blue blooms, how do you identify them?

This guide covers the most common weed species that produce small blue flowers. Learning to recognize these plants will help you understand how to manage them in your yard

Why Identify Blue Flower Weeds?

Weedy plants with tiny blue flowers may not seem like a big concern compared to large aggressively spreading weeds. But even small weeds can cause issues if left uncontrolled, including

• Crowding out desired plants in flower beds or vegetable gardens.

• Disrupting the uniform appearance of ornamental lawns.

• Producing seeds that lead to further infestations.

Properly identifying blue flower weeds allows you to take appropriate control measures. Knowing which species you’re dealing with helps you select effective removal techniques and herbicide options when needed

Some tiny blue flower weeds also have beneficial uses. Identifying edible or medicinal species lets you take advantage of these plants rather than simply removing them as unwanted pests.

Common Tiny Blue Flower Weeds

Here are some of the most frequently seen weeds that produce small blue blooms:

Bluets

Bluets (Houstonia caerulea) produce cheerful little blue or white flowers less than half an inch wide. These hardy winter annuals thrive in moist soils and will spread to form a dense carpet.

Tiny bluets act as an important early spring food source for pollinators. But they can overwhelm garden beds and disrupt the uniformity of turfgrass. Hand pulling is effective for small infestations. Pre-emergent herbicides applied in fall help control larger populations.

Field Speedwell

Field speedwell (Veronica agrestis) is a low-growing annual weed covered in tiny blue flowers from spring through fall. Each bloom has four petals surrounding a yellow center. Speedwell spreads aggressively by rooting at stem nodes.

In healthy lawns, speedwell struggles to gain a foothold. But it can infest thinning or diseased turf. Improve cultural practices to encourage vigorous grass growth. For heavy infestations, broadcast or spot treatment with broadleaf herbicides containing 2,4-D, MCPP, or dicamba provides control.

Germander Speedwell

Similar to field speedwell, germander speedwell (Veronica chamaedrys) forms a mat of small leaves topped by tiny blue blooms. This perennial weed withstands mowing and spreads rapidly through surface stolons.

Combination products containing dicamba or triclopyr work well on germander speedwell. But avoid spraying these herbicides on newly seeded grass. Hand weeding may be a better option for young lawns.

Forget-Me-Not

Garden escapee forget-me-not (Myosotis sylvatica) bears clusters of small, bright blue flowers with yellow eyes. A single plant can produce over 1600 seeds that remain viable up to 30 years. Underground stems (rhizomes) also allow rapid vegetative spread.

Manual removal can work for small infestations, but forget-me-not requires diligence to eradicate. Returning plants missed during hand weeding will quickly re-infest an area. Pre-emergent herbicides or repeated applications of dicamba/triclopyr products help provide more complete control.

Venus’ Looking Glass

Venus’ looking glass (Triodanis perfoliata) displays unique blue flowers with flaring petals and a yellow-tipped pistil. As a winter annual, it forms small basal rosettes through fall and winter before sending up flowering stems in spring.

Pull young plants by hand in early spring to prevent seed production. For established stands, the broadleaf herbicides mentioned above can provide control. But avoid spraying near desirable broadleaf plants.

Blue-Eyed Grass

Despite its name, blue-eyed grass (Sisyrinchium spp.) is actually a member of the iris family. These small perennials produce delicate blue flowers with a yellow center. Grass-like leaves form dense clumps or mats close to the ground.

Blue-eyed grass prefers moist conditions. Improving drainage and soil conditions encourages healthy turf that resists invasion. However, removing established plants requires persistent hand weeding or careful use of broadleaf herbicides.

Less Common Species

While the weeds above represent the most frequently encountered blue flower weeds, you may come across some other species including:

• Asiatic dayflower (Commelina communis) – Low-growing annual with small blue blooms. Spreads aggressively but has edible leaves.

• Blue toadflax (Linaria canadensis) – Cool weather annual that bears tiny snapdragon-like flowers. Young plants pull easily but mature weeds have deep taproots.

• Blue curls (Trichostema lanceolatum) – West coast annual with vivid blue flowers resembling tight ringlets. It colonizes bare ground rapidly.

• Plaintain-leaved pussypaws (Cistanthe grandiflora) – Evergreen perennial with abundant little blue flowers above gray foliage. Spreads via stolons and re-roots from fragmenting stems.

Proper identification remains important before attempting control of any blue flower weeds encountered in your landscape. Pay close attention to each plant’s growth habit, leaf shape, root structure and other distinguishing features.

Control Methods

Tiny weed flowers usually indicate small, tender plant structures that respond well to basic control techniques:

Manual Removal

For limited weed populations, carefully hand pull or hand weed to remove entire plants including the roots. This works best when soil is moist but not saturated. Follow up frequently to eliminate any regrowth.

Use hoes or other tools to slice weeds off just below soil level. Remove and destroy weed debris to prevent re-rooting. Stay shallow to avoid damaging nearby desired plants.

Smothering

Cover small areas of weeds with opaque material to block light and kill the plants. Cardboard, yard waste bags, carpeting or commercial landscape fabrics all work well. Maintain cover for 4-6 weeks until all growth stops.

Selective Herbicides

When manual methods fail, targeted herbicides that kill weeds but not grass can selectively remove blue flower weeds from lawns. Look for products containing 2,4-D, MCPP, dicamba and/or triclopyr.

Carefully follow label directions to avoid harming desired vegetation. New grass seedings and transplants are especially sensitive to these compounds.

Pre-Emergents

Pre-emergent herbicides create a toxic barrier that prevents weed seeds from germinating. Apply these products to areas prone to blue flower weeds in early spring and/or fall. This reduces new weed populations while leaving established plants unaffected.

Prodiamine, pendimethalin and dithiopyr are common pre-emergents for home lawns. Use safely to avoid contaminating vegetable gardens or flower beds.

When to Allow Blue Flower Weeds

While blue flower weeds typically require control to limit their spread, you may decide to tolerate these plants in certain areas:

• Naturalized meadows and informal plantings provide a suitable home for delicate blue blooms. The weeds blend in well with the naturalistic design while attracting pollinators.

• Edible weeds like Asiatic dayflower can be allowed to grow in moderation in gardens where you harvest their leaves. Just be vigilant about preventing excessive seed production.

• Early season bloomers like bluets offer needed forage for emerging pollinators. Allow some plants in out-of-the-way sections of your landscape. Remove them later once other flowers become available.

Even in these areas, it’s wise to monitor blue flower weeds and control any rapid spread. But a limited number of plants can add beauty and wildlife habitat without disrupting your landscape goals.

Tiny blue-flowered weeds may appear harmless. But don’t overlook the need to control their growth. Properly identifying blue weed flowers allows you to select suitable management options. A combination of manual removal, selective herbicides and pre-emergent products can help rid your lawn and gardens of difficult-to-eliminate species.

Yet you may also decide that an occasional blue bloom can be tolerated or even encouraged. Taking advantage of the benefits offered by edible or wildlife-friendly species transforms a weed into a welcome garden visitor.