I had a massive infestation of Purple Deadnettle (Lamium purpureum). I made the classic rookie mistake of trying to spray it in late May, only to realize later that this weed naturally dies off in the summer heat anyway. The damage to my turf was already done.
Controlling this aggressive winter annual requires knowing exactly when to strike and how to fix the underlying soil issues that invited it in the first place. Whether you have a small patch in your garden beds or an entire lawn taken over by this mint-family invader, here is the complete, proven guide on how to get rid of purple deadnettle for good.
Quick Answer: How Do You Get Rid of Purple Deadnettle?
Because it has a shallow root system, the easiest way to remove small patches of purple deadnettle is by hand-pulling when the soil is damp. For severe lawn infestations, apply a post-emergent broadleaf herbicide (containing 2,4-D or dicamba) in the early spring, and use a pre-emergent in the fall to stop next year’s seeds from germinating.
Identification: Is it Purple Deadnettle or Henbit?
Before you start pulling or spraying, you need to know exactly what you are dealing with. Purple deadnettle is often confused with its close cousin, Henbit. Both are winter annuals in the mint family, but deadnettle has some very distinct features.
- Square Stems: Roll the stem between your fingers. If it feels perfectly square, it belongs to the mint family.
- Triangular Leaves: Deadnettle leaves are triangular, slightly fuzzy (hairy), and point downward. The upper leaves develop a distinct reddish-purple tint. (Henbit, on the other hand, has rounded, scalloped leaves).
- Tubular Flowers: It produces tiny, light pink to purple tubular blossoms at the very top of the stem.
Why Did It Invade My Lawn?
Purple deadnettle is an opportunistic weed. It thrives in moist, shaded environments, but its favorite place to grow is in bare, thin, or compacted spots in your lawn. If you mow your grass too short or have areas of exposed dirt during the fall, deadnettle seeds will happily move in.
Effective Removal Methods (Chemical & Organic)
1. Hand-Pulling (The Organic Approach)
If the weed is confined to your garden beds or just a few small patches in the yard, skip the chemicals. Purple deadnettle has an incredibly shallow, fibrous root system. Wait until a day after a heavy rain, grab the weed firmly at the base of the square stem, and pull upward. It usually pops out effortlessly.
2. Post-Emergent Herbicides (For Active Spring Weeds)
If your lawn is completely overrun in March or April, you need a selective post-emergent herbicide. These chemicals are designed to kill broadleaf weeds without harming your turfgrass.
- Look for liquid herbicides containing 2,4-D, Dicamba, or Triclopyr.
- Apply the spray on a calm, sunny day when temperatures are between 60°F and 80°F.
The most effective broadleaf weed killer for spring lawns:
3. Pre-Emergent Weed Control (The Fall Defense)
Because purple deadnettle is a winter annual, the seeds actually germinate in the late summer and early fall, stay dormant over winter, and explode in the spring. To stop the cycle permanently, you must apply a pre-emergent barrier in September.
Stop weed seeds from germinating in the fall:
Common Weed Control Mistakes to Avoid
Homeowners waste hundreds of dollars and hours of labor fighting this weed incorrectly. Do not make these mistakes:
- Spraying in the Summer: Purple deadnettle naturally dies back when the heat of late May and June arrives. Spraying it in the summer is a waste of money; the plant is already dying.
- Using Glyphosate (Roundup) on the Lawn: Glyphosate is a non-selective herbicide. If you spray it on deadnettle hiding in your grass, it will kill the deadnettle AND leave a giant, permanent dead brown spot in your lawn.
- Mowing Without Bagging: If the deadnettle has already produced its purple flowers, do not mow over it and leave the clippings on the lawn. You are just spreading millions of seeds. Bag the clippings and throw them away.
The Ultimate Cure: Turf Density
Nature hates a vacuum. If you have bare dirt in your lawn, weeds will fill it. The absolute best, long-term defense against purple deadnettle is having grass so thick that weed seeds cannot reach the soil.
- Overseed in the Fall: After you apply your pre-emergent and it has run its course, overseed your lawn with high-quality grass seed to fill in the bare patches.
- Mow High: Set your mower deck to 3 or 3.5 inches. Tall grass acts as a canopy, blocking the sunlight that weed seeds desperately need to germinate.
- Aerate: Deadnettle loves compacted soil. Renting a core aerator relieves soil tension, allowing your grass roots to breathe and spread.
Losing the War Against Lawn Weeds?
If your yard is completely overrun and you don’t want to handle chemical herbicides yourself, it is time to call in the professionals. Local lawn care experts can safely apply commercial-grade treatments, aerate your soil, and overseed your lawn to restore its thick, green glory.
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Final Thoughts
Purple deadnettle may be a persistent and annoying weed, but with the right timing, it is highly manageable. Hand-pull small patches, spray broadleaf herbicides early in the spring, and focus heavily on overseeding your lawn in the fall. A thick, healthy lawn is the ultimate weed killer!
Frequently Asked Questions
When is the best time to apply herbicides for purple deadnettle?
Timing is everything. Post-emergent herbicides are most effective in early spring (March or April) when the weeds are young and actively growing. Pre-emergent herbicides must be applied in early fall (September) to prevent the seeds from germinating over the winter.
Can I use household vinegar to kill purple deadnettle?
Household white vinegar (which is only 5% acetic acid) will burn the leaves of the weed, but it rarely penetrates deep enough to kill the root system. Horticultural-grade vinegar (20% to 30% acetic acid) is much more effective, but use extreme caution as it is a non-selective acid that will also burn your grass.
Is purple deadnettle harmful to pets or humans?
No, purple deadnettle is not considered toxic to humans, dogs, or cats. In fact, it is an edible foraging plant often used in salads or teas. However, consuming large quantities could cause mild stomach upset in pets. Always keep pets off the lawn for 24-48 hours after applying chemical herbicides.
What is the difference between purple deadnettle and henbit?
While they look almost identical from a distance, the leaves are the giveaway. Purple deadnettle leaves are distinctly triangular, point downward, and turn a purplish color at the top of the stem. Henbit has deeply scalloped, rounded leaves that clasp directly around the stem without a petiole (leaf stalk).
