Summer of Weeds: Henbit and Purple Deadnettle

There are weeds for every season. Now that we are heading into the hot days of summer, spring weeds (if they haven’t already) are fading. There is a parallel between them and the spring wildflowers we love. They start early, greening up and flowering even before there are leaves on the trees. They exploit the sun made available before deciduous trees and shrubs can hog it all, and they take advantage of the moisture in the soil brought by winter snowfall and spring rain. They thrive in cool temperatures, and their flowers provide early pollen and nectar for emerging pollinators. One major difference between spring ephemeral weeds and spring ephemeral wildflowers is that, despite having similar strategies and providing similar services, the spring weeds aren’t from here; and so we look down on them.

Two common, annual, spring weeds that are easily recognizable – but often mistaken for one another – are henbit and purple deadnettle. Both are in the genus Lamium and the family Lamiaceae (the mint family) and both arrived from Europe. Looking closely at the leaves is the best way to tell these two apart. The upper leaves of henbit (Lamium amplexicaule) lack petioles and are round or oval with rounded teeth. The upper leaves of purple deadnettle (Lamium purpureum) are crowded around the stem, have short petioles, sharper teeth, and are more spade-shaped, coming to a point at the tip. The uppermost leaves of purple deadnettle are a distinct reddish-purple. Identify That Plant offers a great tutorial to help tell these and groundy ivy (another spring-occurring, annual weed in the mint family) apart.

henbit (Lamium amplexicaule)

Henbit prefers full sun and moist, rich soils. It can have either a prostrate or an erect growth habit. In urban environments it is commonly found in lawns, garden beds, and drainage ditches. It is common in agricultural crops and fallow fields as well. According to Weeds of North America, “henbit is poisonous to livestock, especially sheep, causing the animal to stagger;” it is also a host for aster yellows, tobacco etch, and tobacco mosaic viruses. Purple deadnettle inhabits similar sites, often forming a dense groundcover. While henbit and purple deadnettle are highly attractive to bees, they do not always require insect pollination and can self-pollinate instead. Each plant can produce dozens of seeds, and seeds remain viable in the soil for as long as 25 years.

Plants in the genus Lamium are commonly referred to as dead-nettles because they resemble stinging nettle (Urtica dioica) and other plants in the genus Urtica. Lamiums do not posses the stinging quality, and so they are “dead.”  The young leaves, shoots, and flowers of henbit and purple deadnettle are edible and can be eaten raw or cooked. Check out Eat the Weeds for more details.

Illustration of henbit (Lamium amplexicaule) from Selected Weeds of the United States (Agriculture Handbook No. 366) circa 1970

More Resources:

purple deadnettle (Lamium purpureum)

Quote of the Week:

From Wild Urban Plants of the Northeast by Peter Del Tredici

From a utilitarian perspective, a weed is any plant that grows by itself in a place where people do not want it to grow. The term is a value judgment that humans apply to plants we do not like, not a biological characteristic. Calling a plant a weed gives us license to eradicate it. In a similar vein, calling a plant invasive allows us to blame it for ruining the environment when really it is humans who are actually to blame. From the biological perspective, weeds are plants that are adapted to disturbance in all its myriad forms, from bulldozers to acid rain. Their pervasiveness in the urban environment is simply a reflection of the continual disruption that characterizes this habitat. Weeds are the symptoms of environmental degradation, not its cause, and as such they are poised to become increasingly abundant within our lifetimes.

A patch of dead-nettle (Lamium sp.) – photo credit: Amy Trampush (Thank you, Amy!)

Introducing the Summer of Weeds

I spent the first five months of this year posting almost exclusively about invasive species. There is still plenty more to say on the topic, and I’m sure I will get back to that. However, it is time now to dive into the topic that I really want to explore. Weeds.

There is definitely crossover between the two topics – many weeds are invasive species – but there are clear distinctions, too. Oftentimes, weeds as a category of plants are unfairly and unjustly lumped under the title “invasive,” but any plant can be a weed at any moment in time if a human says so. That’s the difference. A plant does not have to prove that it is causing any sort of ecological or economic damage to be called a “weed;” it just has to be growing where a human doesn’t want it to. Yet, too quickly a plant “out of place” is cursed at using words like “invasive” or “noxious” regardless of its origin or behavior. I know I’m being overly semantic about this, but it seems unfair (and incorrect) to lump any and all plants that are bothering us for whatever reason into categories that have legal definitions.

If you can’t already tell, I am obsessed with weeds. It’s a topic I have been thinking about fairly consistently for much of my adult life. For one thing, as part of my career I spend a huge portion of my time killing and controlling weeds. I comprehend fully the visceral reaction of seeing a garden overcome by weeds – the vile thoughts one can have towards a group of plants that are soiling what could otherwise be a beautiful landscape – and I know very well the backbreaking work and countless hours that go into removing uninvited plants (cursing the intruders along the way). I get why weeds are a problem, and I understand why they are a subject of so much vitriol. Yet, over the years I have developed a respect – even a love – for weeds (despite the fact that I still must remove them and that removing them continues to be an overwhelming task).

Unwanted plants have been following us around and getting in our way for millenia. Essentially, we are partners in crime. We intentionally and unintentionally bring plants from various parts of the world on our travels, and through disturbance we create conditions where introduced plants can settle in and thrive. Over time, some once beloved plants grow out of favor and transition from desirable to weedy. As our cycles of disturbance continue, we give early successional, opportunistic plant species a chance to perpetuate themselves, guaranteeing that we will keep such “weeds” with us forever. We reap what we sow; even though we generally don’t plant weeds on purpose, other actions ensure that they will be our constant companions.

The importance of weed control goes beyond the aesthetic. In horticulture and agriculture, weeds compete with crops for light, space, water, and nutrients. They also harbor pests and diseases, and their seeds can contaminate crops. In pastures and rangelands, some weeds poison livestock. Certain weeds are harmful to people, too. Other weeds are simply disruptive – getting tangled up in machinery, damaging infrastructure, blocking our vision along roadways, and even giving cyclists flat tires. Apart from all that, even if all weeds did was make our gardens look unsightly, I imagine we would still be pretty angry with them.

I am interested in weeds wherever they are, but the weeds that fascinate me the most are those that thrive in urban environments. Not necessarily the weeds in our yards, but the weeds that have escaped our fences and property lines; the ones in the margins. We see them in abandoned lots, along roadways, near irrigation channels, and in other neglected spaces. They pop up in the cracks of sidewalks, on rooftops, in the middle of decaying buildings, and anywhere else that people haven’t paid attention to in a while. Urban areas have, for the most part, been scraped of their native flora. Introduced species move in to fill that void. As Richard Mabey writes in his book about weeds, these plants “insinuate the idea of wild nature into places otherwise quite shorn of it;” they are “the very essence of wildness.” Novel ecosystems, like those created by urbanization and human development, are with us whether we like it or not. There is a “wildness” to them that is unlike other cultivated and manicured areas maintained by humans. These urban wild places are worth a closer look.

So, what is the Summer of Weeds?

Put simply, it’s an exploration of weeds. Throughout the summer I will be profiling some of the weeds I come across in my daily life. I will include photos, a brief description, and some interesting facts about each species. I will also include quotes about weeds from various sources, as well as videos, links, resources, and whatever else I come across that seems worth sharing. I hope you enjoy it. If you have anything to add along the way – specifically any personal thoughts or stories to share about weeds – please do. You can contact me via the usual ways: in the comment section below, through the Contact page, or on Twitter, Tumblr, Facebook, or Instagram. Happy Summer!