Why There Is No Such Thing as a Weed

Table of Contents

How a term shapes our perception of wild plants—and why some supposed “weeds” are now themselves under threat.

“How to get rid of ground elder,” “Strategies for controlling thistles,” “How to eliminate weeds from your lawn for good,” or “How to get rid of weeds forever”: As gardening season begins, headlines like these regularly return to magazines and online guides. Hardly any other group of living organisms is so routinely associated with words such as control, eradicate, or eliminate as so-called weeds.

But what exactly is a weed? From a botanical perspective, the answer is simple: there is no such thing. “Weed” is not a scientific category of plants, but a human value judgment. Dandelions, nettles, thistles, and ground elder are distinct species with a long evolutionary history, special adaptations, and diverse relationships with other organisms. They become undesirable only because of where they grow—or, more precisely, because of our expectations for that place.

A dandelion is considered a nuisance on a closely mown lawn, while a thistle in a wheat field is seen as competing with the crop. On a dry meadow, however, that same thistle can be a valuable source of nectar. For the caterpillars of various butterflies, the stinging nettle is not a bothersome wild plant, but food. And for the European goldfinch, thistle seeds are not a nuisance, but a vital resource.

The term “weed” therefore says less about a plant than it does about the person looking at it. We decide which species seem useful, beautiful, and desirable and which are growing in supposedly the wrong place.

Where does the term “Weed” come from?

The history of the weed concept begins with agriculture. When people started deliberately cultivating plants, other species growing in the same area became competitors: they competed for light, water, and nutrients, made harvesting more difficult, or contaminated seed and harvested produce.

About 7,000 years ago, the first farmers also brought typical arable wild plants from the Middle East to Europe. Later, more species arrived through trade and the transport of seed. Plants that became established before 1492 are known as archaeophytes, while those introduced later are called neophytes.

Originally, then, “weed” referred to plants that interfered with the cultivation of crops. The term becomes problematic when it is applied indiscriminately to every plant that grows spontaneously.

When even “Weeds” become rare

The success of efforts to control unwanted plants is evident, ironically, in some of the formerly typical “weeds.” Many arable wild plants that once regularly grew among cereal crops are now rare or have almost disappeared.

For centuries, these species were part of the European cultural landscape. They were adapted to regular soil cultivation, open spaces among crops, and nutrient-poor fields. Modern agriculture fundamentally changed these conditions.

The current Red List of ferns and flowering plants in Germany lists numerous traditional arable wild plants as threatened:

• Common corn-cockle (Agrostemma githago) – endangered
• Hybrid Venus’s looking-glass (Legousia hybrida) – endangered
• Summer pheasant’s eye (Adonis aestivalis) – endangered
• Large pheasant’s eye or flame adonis (Adonis flammea) – critically endangered
• Small bur-parsley (Caucalis platycarpos) – endangered
• Shepherd’s needle (Scandix pecten-veneris) – endangered
• Wild fennel flower (Nigella arvensis) – critically endangered

Cleaner seed, herbicides, denser crop stands, heavier fertilization, and altered crop rotations have drastically reduced arable flora. The same changes that made cultivation more productive and predictable also eliminated the habitats of many specialized species.

The corn-cockle, for example, was once a problematic weed in cereal fields because its poisonous seeds could contaminate the harvested grain. Today, modern seed cleaning and weed control mean that it is rarely found in fields. A once-targeted “weed” has become an endangered species.

Wild plants are also disappearing outside fields. White horehound (Marrubium vulgare) is considered critically endangered in Germany, motherwort (Leonurus cardiaca) endangered, and Good-King-Henry (Chenopodium bonus-henricus) vulnerable. They were once part of the characteristic flora of old villages, farmsteads, roadsides, and walls.

Their habitats are lost when farmyards are paved over, walls are renovated, roadsides are mown frequently, and unmanaged areas are systematically tidied up. What disappears is not just wild growth, but an entire plant community that has long been associated with human settlements.

The word “weed” conveys an impression of abundance and indestructibility. Yet there is no way to tell by looking at a plant how rare it has become. What appears to be ordinary wild growth on a wall may already have almost disappeared from a region. A plant can be unwanted in one place while simultaneously being at risk of disappearing throughout Germany.

What “Weeds” do for ecosystems

When wild plants disappear, we lose not only individual species, but also their functions in the ecosystem. Many provide nectar, pollen, leaves, or seeds over long periods. Thistles first feed pollinators and later seed-eating birds such as the European goldfinch. Stinging nettles provide food for the caterpillars of several butterfly species. Plantains, dandelions, and numerous inconspicuous herbs are used by insects that, in turn, serve as food for birds and other animals.

A 2022 study by Nicholas Balfour and Francis Ratnieks demonstrated just how great this value can be. Some of the “weeds” officially classified as harmful in the United Kingdom supported a particularly large number of pollinator species—in some cases more than did plants specifically selected for agri-environment schemes. A plant’s poor reputation therefore says little about its importance to insects.

Wild plants can also protect the soil. Continuous plant cover can reduce drying, surface runoff, and erosion. In fields and vineyards, on embankments, and even in the joints between paving stones, it covers bare soil and breaks up surfaces that become intensely hot. In cities, such small islands of vegetation can retain moisture and help cool the local environment.

Mosses also perform important functions. They store water, protect their immediate surroundings from drying out, and create habitats for microorganisms and small invertebrates on soil, walls, rocks, or between paving stones.

Even in agriculture, wild plants are not exclusively competitors. Flowering arable wild plants provide food for parasitoid wasps, hoverflies, and other natural enemies of pests. This means they can support biological pest control and help reduce the need for insecticides.

Another important role is that of a genetic reservoir. Wild plants and wild relatives of our crops preserve a great diversity of genetic material. This may include traits that will become important for future breeding—such as resistance to drought, disease, or changing climate conditions. Other supposed weeds, such as chamomile, ribwort plantain, and ground elder, have long been used as medicinal or food plants.

This does not mean that every species is unproblematic in every location. In fields, individual plants can cause substantial yield losses, while invasive species can alter native ecological communities. The crucial question is therefore not whether a plant is categorically “good” or “bad,” but which species is growing where and what effects it has there.

Why we remove them anyway

Why are wild plants removed so frequently despite their ecological value? Often, it has less to do with the plants themselves than with our idea of order. We recognize a flower bed with roses or dahlias as designed and well maintained. A diverse plant community on a vacant lot, against a wall, or between paving stones, by contrast, appears to be wild growth or neglect.

This applies not only to wild herbaceous plants. Mosses are also removed from sidewalks, walls, or roofs, even though they generally pose no ecological problem there, but instead retain moisture and form small habitats.

The 2021 study Just weeds? compared the measured species richness of spontaneous urban vegetation with how observers perceived it. These plant communities made a substantial contribution to biodiversity, yet their ecological value was often underestimated.

How valuable unplanned vegetation can be is also demonstrated by urban wastelands. In a 2025 study from central Germany, they were at least as valuable to wild bees as the Natura 2000 sites examined.

Language also shapes how we see things. Hardly anyone would campaign to protect “weeds.” Call the same plant a wild plant, crop-associated plant, or nectar plant, and it appears in a different light. The word “weed” therefore does not merely describe a plant; it already contains a judgment about it.

Less derogatory alternatives often used in German include Beikraut, Wildkraut, and Kulturpflanzenbegleiter. However, they emphasize different aspects. “Beikraut” mainly refers to plants that grow alongside crops. “Kulturpflanzenbegleiter” emphasizes their connection with agriculture. Outside agricultural land, “wild plant” or “wild herb” is usually more accurate.

None of these terms automatically makes a plant valuable or unproblematic, but they avoid the premature judgment already inherent in the word “weed”. Before deciding whether a plant is a nuisance, we should first find out what species it is and what role it may play in that location.

A weed is in the eye of the beholder

“Weed” is neither a botanical category nor a characteristic of a plant. Rather, it is a judgment about whether a plant is desirable in a particular place.

That judgment can sometimes be reasonable—for example, in a field, along a road or path, or in the case of invasive species. It becomes problematic when a specific assessment turns into a blanket attitude and every plant that grows spontaneously is automatically considered a nuisance.

Perhaps the first question should not be how to get rid of a plant, but rather: What species is growing here, why is it growing in this particular place—and what would disappear along with it?

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Sources

• Balfour, N. J., & Ratnieks, F. L. W. (2022). The disproportionate value of ‘weeds’ to pollinators and biodiversity. Journal of Applied Ecology, 59, 1209–1218. https://doi.org/10.1111/1365-2664.14132
• Phillips, D., & Lindquist, M. (2021). Just weeds? Comparing assessed and perceived biodiversity of urban spontaneous vegetation in informal greenspaces in the context of two American legacy cities. Urban Forestry and Urban Greening, 62, 127151. https://doi.org/10.1016/j.ufug.2021.127151
• Theodorou, P., Osterman, W. H. A., Mrozek, J. H., et al. (2025). Protected areas do not outperform urban wastelands in supporting insect pollinators and pollination in central Germany. Basic and Applied Ecology, 84, 29–39. https://doi.org/10.1016/j.baae.2025.02.001