Many of the most noticeable weedy species that bloom early in the season feature purple flowers. This coloration is a biological advantage, as the anthocyanin pigments responsible for the purple hue help the plant absorb light more efficiently in cooler temperatures. These bright colors also attract early-season pollinators, allowing the plants to complete their life cycle quickly before being shaded out by summer growth.
Widespread Weeds with Distinct Purple Blooms
Three of the most frequently encountered weeds sporting purple flowers are Henbit, Purple Deadnettle, and Creeping Charlie. Henbit (Lamium amplexicaule) is a winter annual that forms low-growing, sprawling patches in thin lawns and garden beds, becoming noticeable in early spring. Its pinkish-purple, tubular flowers appear in whorls around the upper portions of the stem, often attracting honeybees. The plant usually remains under a foot tall until it begins its spring bloom.
Purple Deadnettle (Lamium purpureum) is a winter annual that flourishes in disturbed soil. This plant is distinguished by the reddish or purple tint of its newest leaves, which are clustered near the top of the stem, surrounding the small, purplish-pink flowers. It tends to grow more upright than Henbit, reaching heights of four to eight inches. The distinctive leaf color and hooded flowers make this species one of the earliest signs of spring.
Creeping Charlie (Glechoma hederacea) is a vigorous perennial that forms dense, carpet-like mats, especially in moist, shady areas. Its light blue to bluish-purple flowers are small, funnel-shaped, and appear in clusters of two or three at the leaf axils along its trailing stems. Unlike the two annuals, Creeping Charlie is difficult to remove once established because of its perennial nature.
Key Features for Accurate Identification
Accurate identification relies on examining specific structural clues beyond just the flower color. Henbit, Purple Deadnettle, and Creeping Charlie are all members of the mint family, meaning they possess characteristic square, four-sided stems. Rolling the stem between your fingers confirms this unique shape, instantly separating them from rounded-stemmed weeds.
The difference between Henbit and Purple Deadnettle is most clearly found in the upper leaves. Henbit’s upper leaves are sessile, lacking a stalk, and appear to wrap around the stem. Purple Deadnettle retains short stalks, or petioles, on all its leaves, even those directly beneath the flowers. Additionally, Deadnettle’s upper leaves often have a striking purple or reddish coloration, which is less pronounced in Henbit.
Creeping Charlie is a perennial with a different growth strategy. It spreads aggressively by sending out long, above-ground stems called stolons that root at the nodes to form new plants. Its leaves are distinct, being rounded or kidney-shaped with scalloped edges, and are arranged opposite each other on the square stem. Crushing the leaves often releases a faint, minty aroma.
Safety and Toxicity Considerations
While many purple-flowered weeds are harmless, some common species can pose serious health risks. Frequent invaders like Henbit and Wild Violet (Viola spp.) are generally non-toxic to humans and pets. Purple Deadnettle is also non-toxic and is often foraged for its tender leaves.
Other purple-flowered weeds can be dangerous. Creeping Charlie is toxic to horses, potentially causing digestive and nervous system issues if consumed in large quantities. More concerning are Nightshade species (Solanum spp.), which have purple flowers and are highly toxic due to solanine alkaloids. Ingestion of Nightshade berries or leaves can lead to severe gastrointestinal distress and neurological symptoms in humans or pets.
Positively identify any plant before handling or consuming it, as some toxic varieties have harmless look-alikes. Other purple-blooming weeds, such as certain Thistles, are not chemically poisonous but present a physical hazard due to sharp spines that can irritate skin or injure pets. Accurate identification determines the appropriate safety measures.
Effective Management and Removal
The most effective control strategy depends on the weed’s life cycle. Henbit and Purple Deadnettle are winter annuals; they germinate in the fall, survive the winter, and produce seed in the spring before dying in the summer heat. Managing them is easiest in the fall or very early spring before they set seed.
Manual removal is straightforward for these annuals because they possess shallow, fibrous root systems that pull out easily from moist soil. Applying a pre-emergent herbicide in late summer or early fall prevents the seeds from germinating. Post-emergent broadleaf herbicides containing ingredients like 2,4-D or dicamba can also be used in the spring when the plants are actively growing.
Controlling perennial weeds like Creeping Charlie and Wild Violets is difficult due to their extensive root systems and ability to spread vegetatively. Hand-pulling is often insufficient because any leftover rhizome fragments can regrow into new plants. Herbicides containing triclopyr are required for effective control of these perennial broadleaf weeds. Applications are most effective in the fall, as the plants are actively moving nutrients to their roots, carrying the herbicide along with them.
Maintaining a dense, healthy lawn is the best preventative measure against all purple-flowered weeds. Proper mowing height, watering, and fertilization create a thick turf canopy that crowds out weed seedlings and prevents establishment. For Creeping Charlie, improving soil drainage and reducing excessive shade discourages its growth, as it thrives in damp, dark conditions.