Purple Deadnettle (Lamium purpureum L.)

↑Habitat

Mostly found in moist, exposed areas with fertile soil.

This plant has benefitted hugely from human management of the landscape. It thrives in agricultural areas, where it is often found in fallow fields and often is able to complete its lifecycle over the winter. In urban and suburban areas, it benefits from management practices which expose the soil.

It is often able to set seed before mowing begins in spring, so it is sometimes found in lawns, especially small patches of grass and at margins of lawns.

↑Life Cycle

This plant is an annual, usually a winter annual, less commonly growing at other times of year.

Seeds usually sprout in fall but the plant remains small. Young plants have rounded leaves of a solid green color, very different from what the plant looks like at maturity. Initially, the plant usually grows out against the ground in a sprawling habit. Unlike many mint-family plants, it does not frequently root at the nodes, instead usually staying connected to its root system only at a single point where the plant sprouted.

The root system is often quite shallow, forming a mat that follows areas of moist, rich soil.

In late winter and early spring, the plant begins growing upright, and the leaves take on a more pointed shape and purplish hue, and it then blooms. Plants usually die down in summer after producing seeds.

Some late-sprouting plants, however, can grow in summer, especially in cooler years. In summer, the plant prefers more shaded, protected, and moist locations than in winter where it can grow in more exposed areas.

Seeds require exposed conditions to germinate.

↑Control

This plant can be difficult to completely remove from a site because it has high seed production, tiny seeds, and its seeds can remain viable for many years. It is also abundant in areas where it is established, and its tiny seeds spread readily, leading to a high likelihood of reestablishment. However, reduction strategies can be effective and usually reduce this plant to isolated individuals that can be easily hand-pulled. Control is most effective if surrounding property owners or land managers cooperate and carry out removal at the same time.

Control of this plant must be targetted before it sets seed, as it has a short lifecycle and produces much seed rapidly through self-pollination. Because the bloom time is staggered and can sometimes be irregular, it is safest to remove it before the first blooms appear; waiting until you notice blooms may enable some plants to set seed. Warm spells during winter are often the best time to conduct control. Monitoring the area year-round and acting quickly to pull plants is also important because some plants can occasionally bloom and set seed in fall, or rarely, at other times of year.

Isolated plants can be pulled by hand. Because this plant tends to occur in loose, rich soil and have a shallow, spreading root system, and benefits from soil disturbance, it is important to minimize soil disturbance when pulling it. One hand can grab the base of the plant's stem while the other remains closed under it to keep soil from being pulled up as you pull individual plants. Alternatively, plants can be cut to the base, and will not usually resprout. Although plants are capable of re-rooting, they are fragile and will usually die rapidly if left in place on a dry spot. Cutting to the base is most effective if done right before plants bloom. Larger infestations can be reduced by mowing or weedwhacking right before plants begin to bloom.

Although this plant is vulnerable to numerous herbicides, herbicides can often worsen infestations of this plant by killing non-target species that compete with it and creating more spaces for its seeds to germinate. Herbicides are most suitable for dealing with large infestations on sites where all native plants are fully dormant at the time of application.

This plant can be suppressed by establishing native plants with evergreen or semievergreen basal foliage, which will prevent its germination and establishment, and by minimizing soil disturbance and vegetation-removing disturbance such as mowing or weedwhacking in fall and winter. Thick, coarse, slow-decomposing leaf litter can also inhibit this plant, although it can thrive in faster-decomposing leaf litter as it often has enough space to germinate and can take advantage of the high nutrient availability.

↑Links & External Resources

• Lamium purpureum (Purple Dead Nettle) | Illinois Wildflowers (About This Site)

• Lamium purpureum (Purple Deadnettle) | USDA PLANTS Database (About This Site)

• Lamium purpureum | Go Botany (About This Site)

• Lamium purpureum | Biota of North America Project (BONAP) (About This Site)

• Lamium purpureum | NatureServe Explorer (About This Site)

• Lamium purpureum | Missouri Plants (About This Site)

• Purple Deadnettle | Maryland Biodiversity Project (About This Site)