Purple deadnettle (Lamium purpureum)

Common Names: Red deadnettle, purple archangel

Description:

Purple deadnettle (Lamium purpureum) is a low, square-stemmed winter annual in the mint family, native to Europe, the Mediterranean, and east into western Siberia [1]. It is not native to Michigan, and it grows in gardens, fields, ditches, woodland edges, and other disturbed ground [2][4]. MISIN tracks it because it carpets bare soil in early spring while almost nothing else is up, and because it hosts soybean cyst nematode ? a serious crop pest ? through the winter months when no soybeans are in the ground [3][7].

Habit:

Purple deadnettle is a small plant, with branches reaching up to about a foot tall from a spreading base [5]. Roll a stem between your fingers and you will feel four flat sides ? it is a mint, and square stems are the family's signature [4][5]. The stems are mostly smooth, and the lower part is often bare of leaves [4]. The leaves are opposite, triangular to egg-shaped, softly hairy but never shiny, deeply veined so they look crinkled, and scalloped around the edge [4][5].

The top of the plant is the giveaway. The upper leaves crowd together toward the stem tip, droop downward, and flush purple to reddish, so a patch reads as a low carpet with purple tops [4][5]. Tucked among them are small hooded pink-to-purple tubular flowers, arranged in whorls where the upper leaves meet the stem [4][5].

It runs on an upside-down calendar, and that is what makes it easy to find. Most plants come up in fall, sit low through winter, then flower and set seed in early spring ? and die off once hot, dry weather arrives in late May and June [3]. So look for it in March through May, when it covers bare gardens and field edges while the rest of the yard is still brown. By midsummer it has vanished, seed already in the soil [3].

At-a-glance cues:

1. Square stems you can feel by rolling one between your fingers [4][5]
2. Upper leaves crowded, drooping, and flushed purple to reddish toward the stem tip [4][5]
3. Small hooded pink-to-purple tubular flowers in whorls among the upper leaves [4][5]
4. Carpets bare ground in early spring, then disappears by early summer [3]

Leaves:

1. Arrangement: opposite ? two leaves per node [4]
2. Shape: triangular to egg-shaped [4]
3. Margin: scalloped [4]
4. Venation: deeply veined, giving a crinkled or quilted look [4]
5. Surface: covered in soft hairs, never shiny [4][5]
6. Color: upper leaves flushed purple to reddish near the stem tip; lower, older leaves dull green [4][5]
7. Attachment: lower leaves on long stalks; upper leaves on very short stalks that do not clasp the stem, and the leaves beneath the flowers bend downward [2][5]

Stems:

1. Habit: a low winter annual, usually branching from a spreading base [3][5]
2. Height: branches reach up to about a foot tall [5]
3. Cross-section: square ? four distinct flat sides, the mint-family trait [4][5]
4. Surface: largely smooth, with the lower portion often bare of leaves [4]
5. Rooting: lower nodes may put down roots where they touch the ground [5]

Flowers:

1. Color: pink to purple [4][5]
2. Shape: small and tubular, two-lipped and hooded, the lower lip split into two rounded lobes [4]
3. Size: the flower tube is roughly 9 to 19 mm long and straight, not curved [2]
4. Arrangement: in whorls where the upper leaves meet the stem, with a cluster at the top of each stem [4]
5. Bloom time: early spring, with seed set following shortly after [3]

Fruit and seeds:

1. Fruit type: each flower forms four small nutlets [4]
2. Color and surface: brown and slightly bristly [4]
3. Ripening: early spring, soon after flowering [3]
4. Output: roughly 27,000 seeds per plant [3]
5. Germination: seedlings come up mainly from the top inch of soil, chiefly in fall [3]
6. Dispersal: no wings or fluff ? seed drops near the parent and moves in soil, on tools, and on equipment [4]

Habitat:

Purple deadnettle is native to Europe, the Mediterranean region, and east into western Siberia [1]. It is not native to Michigan and is now widespread across North America [4][6]. Every one of the four Lamium species growing wild in Michigan came from Europe ? two are garden plants that escaped, and purple deadnettle is one of the two that behave as weeds [2].

It is a plant of worked and disturbed ground rather than intact habitat. Look for it in gardens, cultivated fields, ditches, drainage canals, woodland edges, waste ground, and other disturbed sites [4][5]. It does best on rich soil ? nutrient-rich, mildly humic loams and sandy loams suit it [3][5].

In farm settings it is chiefly a problem of small grains, alfalfa, and no-tillage systems, where the ground is not turned over between crops and its fall seedlings are left undisturbed [3]. Bare, rich, untilled soil in autumn is exactly the opening it needs.

Reproduction:

Purple deadnettle spreads by seed, and it makes a great deal of it ? roughly 27,000 seeds from a single plant [3][4]. The seed has no wings or fluff, so it mostly drops close to the parent rather than blowing away. It travels when soil travels: on boots, tools, tires, and tillage equipment. Lower branches may also root where they touch the ground, which lets an individual plant spread a little sideways, though the plant is still an annual [5].

The life cycle is the thing to understand, because it explains why this weed so often wins. Purple deadnettle is a winter annual. Seedlings come up mainly in the fall, from the top inch of soil [3]. They sit low through winter, green and inconspicuous. Then they flower and set seed in early spring, before most gardeners have started working, and die off when hot, dry weather arrives in late May and June [3].

That means by the time you notice the purple carpet in April, the plant may already be finishing its work. The control window is earlier than instinct suggests: fall, when the seedlings appear, or the very start of spring, before flowers open. Waiting until the patch looks like a problem generally means the next generation of seed is already in the ground [3].

Impact and Damage:

Despite the name, purple deadnettle is not a nettle at all ? it is a mint, in a different plant family from stinging nettle, and it has no stinging hairs [1][2]. The "dead" in deadnettle refers exactly to that: nettle-shaped leaves that cannot sting.

For a homeowner, the practical complaint is that it takes the ground when nothing else is competing for it. It carpets bare soil in gardens, beds, and field edges in early spring, and it favors exactly the rich, worked soil people cultivate [3][5]. It is a competitor for space and a nuisance rather than a plant that damages anything.

The serious impact is agricultural, and it is indirect. Purple deadnettle is an alternate host for soybean cyst nematode, one of the costliest pests of soybean. Because the weed is green all winter when no soybean crop is in the field, it acts as a bridge that carries the nematode across the gap between crops. In field experiments in continuous no-till soybean, plots where purple deadnettle emerged in early October ended with nematode egg population change factors of 7.28 to 11.41 ? three- to fivefold higher than weed-free plots or plots where the weed emerged in September [7]. The timing of emergence, not just its presence, drove how much the nematode population grew.

For natural area stewards, this is a low-tier concern. Purple deadnettle is a weed of gardens, crop fields, and disturbed ground, and it dies back on its own by early summer [3][5]. It turns up along woodland edges and other disturbed margins rather than sweeping through intact plant communities [4]. The management value is in cultivated and disturbed ground, not in the interior of a healthy natural area.

Similar species:

Purple deadnettle is easily confused with the other deadnettles, all of which came here from Europe [2]. The flowers and the way the upper leaves attach separate them.

Henbit (Lamium amplexicaule) is by far the most common mix-up ? both are low European winter annuals with square stems and small pink-purple hooded flowers, and they often grow side by side in the same field [2]. Look at the leaves just below the flowers. On henbit they have no stalk at all and wrap right around the stem, and they point upward or sit horizontal [2][5]. On purple deadnettle those same leaves have a short stalk, do not clasp the stem, and bend downward [2][5]. Henbit's floral leaves are also a bit wider than long, roughly kidney-shaped in outline, where purple deadnettle's are about as long as wide [2].

Spotted dead-nettle (Lamium maculatum) is a garden plant that escapes, and it is easy to separate once you look closely [2]. It is a perennial with much larger pink to purplish flowers ? the tube runs about 19 to 26 mm and curves upward, where purple deadnettle's is 9 to 19 mm and straight [2]. The clincher is on the leaf: spotted dead-nettle carries a white streak down the midvein, which purple deadnettle never has [2].

White dead-nettle (Lamium album) is the other large-flowered garden escape, and its flowers are white rather than pink or purple, which settles it at a glance in bloom [2]. It is a perennial with the same big, upward-curving flower tube of about 19 to 26 mm, its leaves are all plain green, and the upper lip of the flower is fringed with long hairs [2].

Monitoring and rapid response:

Signs to watch for:

1. In fall, small green seedlings coming up across bare, worked soil ? this is the stage most people miss [3]
2. From March through May, low carpets with purple-flushed tops across gardens, beds, field edges, and ditches while the rest of the yard is still bare [3][5]
3. Square stems and small hooded pink-purple flowers in whorls among the crowded upper leaves [4][5]
4. In no-till fields, small grains, or alfalfa, a green mat holding through the winter ? the situation that matters most agriculturally [3]

What you can do:

1. Act in fall or very early spring. This is a winter annual that flowers and sets seed in early spring, so by the time the purple carpet is obvious it may already be seeding [3]. Fall seedlings and pre-bloom spring plants are the targets.
2. Pull or hoe it. It is a shallow-rooted annual with no creeping roots, so it comes out easily and does not resprout from what you leave behind [3][4].
3. Hoe or till the top inch. Seedlings emerge from the top inch of soil or less, and tillage in late fall or early spring controls the plant readily [3].
4. Bag flowering plants rather than composting them. A single plant carries roughly 27,000 seeds, and pulled plants can still ripen what they are holding [3].
5. Cover the bare ground. Mulch or a dense planting denies the fall seedlings the open soil they need ? in small grains, planting at higher populations suppresses it [3].
6. Do not wait it out. The plant dies on its own with hot, dry weather in late May and June, but by then the seed is already in the soil for next fall, so letting it finish is not control [3].
7. Natural area crews can safely deprioritize this one relative to habitat invaders and focus effort where it matters: cultivated ground, garden beds, staging areas, and disturbed margins. It does not persist through the summer or push into intact plant communities [3][4].

When to call a professional:

1. You farm soybeans, or rotate into them, and purple deadnettle is overwintering in your fields. It is an alternate host for soybean cyst nematode and its emergence timing measurably drives nematode buildup, so an agronomist or extension crop advisor can build the rotation and timing plan around that [7].
2. The infestation covers cropland at a scale where hand tools and tillage timing are not keeping up [3].
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Plants of the World Online. Lamium purpureum L. Royal Botanic Gardens, Kew. powo.science.kew.org
2. Reznicek AA, Voss EG, Walters BS (2011). Lamium. Michigan Flora Online, University of Michigan. michiganflora.net
3. Michigan State University Extension. Purple deadnettle ? MSU Weed Science. canr.msu.edu
4. Michigan State University Plant & Pest Diagnostics. Purple Deadnettle ? Lamium purpureum L. canr.msu.edu
5. Washington State University Hortsense. Weeds: Purple deadnettle (red deadnettle) ? Lamium purpureum. hortsense.cahnrs.wsu.edu
6. USDA NRCS Plants Database. Lamium purpureum L. (purple deadnettle), symbol LAPU2. plants.usda.gov
7. Harrison SK, Venkatesh R, Riedel RM (2008). "Purple deadnettle (Lamium purpureum) emergence and removal time effects on soybean cyst nematode (Heterodera glycines)." Weed Science 56(2):327?335. semanticscholar.org

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