Purple dead nettle (Lamium purpureum) is a common plant that appears in lawns and gardens every spring, often causing confusion about its true nature. Many people wonder if this fast-growing species is simply a nuisance weed or a more problematic invasive species. It is accurately classified as a highly successful non-native weed, and understanding its life cycle can help clarify its presence. This article aims to settle the debate about its classification and provide practical information on managing and utilizing this ubiquitous plant.
Identification and Growth Characteristics
Purple dead nettle belongs to the mint family, Lamiaceae, and is identifiable by its characteristic square stems. It is a winter annual that grows low to the ground, rarely exceeding 12 inches in height. Seeds germinate in the fall, the plants overwinter as rosettes, and then grow rapidly, flower, and set seed in the early spring before summer heat arrives.
The leaves are opposite, heart- or triangular-shaped, and covered in fine hairs. A defining feature is the color transition where the upper leaves turn a distinctive purplish or reddish hue. Small, tubular pink or purple flowers appear in the axils of these upper leaves.
Purple dead nettle is often mistaken for henbit (Lamium amplexicaule). Purple dead nettle has short leaf stalks (petioles) connecting all its leaves to the stem, while henbit’s upper leaves directly clasp the stem. The plant is a prolific seed producer, with a single plant capable of generating over 27,000 seeds in one season.
Determining the Status: Weed or Invasive Species?
The distinction between a “weed” and an “invasive species” is important. A weed is simply any plant growing where it is not wanted, while an invasive species is defined as a non-native organism that causes or is likely to cause economic or environmental harm. Purple dead nettle is native to Eurasia but has been widely introduced and naturalized across North America.
The plant is accurately classified as a non-native, naturalized weed. It is highly competitive, especially in disturbed soils, gardens, and thin turf. Its rapid spring growth allows it to outcompete desired plants for light, water, and nutrients before they have fully emerged.
It does not typically meet the regulatory threshold for an “invasive species” in most regions of the United States. Unlike true invaders, it generally dies back completely by late spring or early summer, allowing summer plants to take over. Some regional organizations, however, list it as a moderate threat due to its potential to spread rapidly in specific localized areas.
Practical Removal and Control Methods
Control is achieved by targeting the plant’s winter annual life cycle. Prevention is the most effective method, focusing on creating a dense and healthy turf that crowds out space for the weed to germinate. Proper cultural practices, such as correct mowing height and appropriate fertilization, can thicken the grass stand and provide natural suppression.
For existing, small patches, manually removing the plant before it flowers and sets seed is highly effective. Preventing seed drop is the key to long-term control since the plant dies after seeding. Hand-pulling is easiest when the soil is moist, ensuring the entire fibrous root system is removed.
In larger infestations, chemical control may be necessary, and timing is paramount. Pre-emergent herbicides are applied in the late summer or early fall to prevent germination. For plants already growing in the spring, a selective post-emergent herbicide containing compounds like 2,4-D or dicamba can be used, but this must be applied before the plant matures and releases its seeds.
Foraging and Other Uses
Despite its weed status, purple dead nettle has beneficial uses that lead some people to tolerate its presence. As one of the earliest plants to flower in the spring, it provides a vital, early-season source of nectar and pollen for pollinators, especially honeybees and bumblebees.
The plant is entirely edible and has been used for centuries in culinary and medicinal traditions. The leaves, stems, and flowers can be foraged, offering nutrients like Vitamin C, iron, and fiber. Although the leaves have a slightly fuzzy texture, they are often used raw in salads or cooked in soups and stir-fries like other leafy greens.
In herbalism, purple dead nettle contains polyphenol compounds, which offer antioxidant properties. It has been used externally as a poultice for minor cuts and wounds due to its mild astringent and anti-inflammatory properties. Internally, it is consumed as a tea or tincture, with traditional uses including relief from seasonal allergies.