What plants are used as indicators?

Plants are commonly used as indicators in various fields, including environmental science, ecology, and agriculture, to monitor and assess specific environmental conditions, health, or changes. Here are several types of indicator plants and their uses:

  1. Indicator Species for Environmental Pollution:
    • Lichen: Lichens are often used to assess air quality. They are sensitive to air pollutants such as sulfur dioxide and can indicate the presence of pollutants in the atmosphere.
    • Mosses: Mosses can accumulate heavy metals and other pollutants from the air and water, making them useful in monitoring pollution levels in certain areas.
    • Aquatic Plants: Some aquatic plants, such as watercress, can be used to detect and monitor water pollution. Changes in plant health or growth can indicate water quality issues.
  2. Indicator Plants for Soil Health:
    • Clover and Legumes: These plants are known for their ability to fix nitrogen from the air into the soil, enhancing soil fertility. Their presence can indicate good soil health.
    • Sunflower: Sunflowers are used to extract heavy metals from contaminated soils, a process called phytoremediation. They can indicate soil contamination levels.
  3. Plant Species for Ecological Assessments:
    • Indicator Plants for Wetlands: Plants like cattails, sedges, and wetland rushes are used to assess the health and ecological quality of wetland environments.
    • Indicator Trees: Certain tree species, like the sugar maple, are used to assess the health of forest ecosystems. Changes in tree health can provide insights into the overall well-being of the forest.
  4. Phenology Indicators:
    • Flowering and Leafing Out: The timing of flowering or leafing out in specific plant species can be used to monitor changes in climate and seasonal patterns.
    • Migration Patterns: Some plants act as indicators for animal behavior, such as the blooming of specific flowers coinciding with the arrival of migratory birds.
  5. Agricultural Indicator Plants:
    • Weeds and Pest-Resistant Plants: The presence of certain weeds can indicate specific soil conditions or nutrient imbalances. Some plants are also resistant to certain pests, and their presence can suggest the potential for pest infestations.
  6. Native and Invasive Species:
    • The presence of invasive plant species can indicate ecological disturbances and can be used to monitor the spread of invasive species in an ecosystem.
    • The absence or decline of native plant species can also be an indicator of ecological disruption or degradation.
  7. Medicinal and Herbal Plants:
    • The presence of specific medicinal or herbal plants can indicate the suitability of soil and environmental conditions for their growth. Traditional herbalists often use indicator plants to locate valuable herbs.
  8. Plant Health Monitoring in Agriculture:
    • Farmers use indicator plants to monitor crop health and nutrient deficiencies. For example, certain plants like clover can indicate nitrogen levels in the soil, benefiting crop management.
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These are just a few examples of how plants are used as indicators in different contexts to assess environmental conditions, ecological health, and other factors. The choice of indicator plant depends on the specific information or conditions being assessed.

Chickweed and franciscus: nutrient-rich soil

Soil in which chickweed grows is also ideal for many useful and ornamental plants, because the inconspicuous herb indicates nutrient- and humus-rich, loose soil. When you pull out chickweed, don’t throw it away, but process it into chickweed pesto and other goodies.

The franciscus herb also feels comfortable only on nutrient-rich humus. It can also be used in many ways for smoothies, pesto and as a substitute for spinach, as well as for medicinal purposes. Other plants that display lots of nutrients and humus in the soil include chamomile, white goosefoot and Persian speedwell. You can use a piece of soil with these properties without further preparation. Since “weeds” also thrive here, it is advisable to plant the soil between each crop with ground covers that inhibit the growth of unwanted herbs.

Nettle and goutweed: nitrogen-rich soil

If there are a lot of nettles growing on the soil you want to plant, you can rejoice! They indicate a nitrogen-rich soil, which favors the growth of many plants. Plus, you can turn nettles into nutrient-rich nettle liquid manure or use them as a wonder herb for cooking and health. Goutweed also feels at home exclusively in nitrogen-rich soil. It can be made into spreads, salads and pesto.

A soil where chickweed grows is also perfect for many useful and ornamental plants, because the inconspicuous herb indicates nutrient- and humus-rich, loose soil. When you pull out chickweed, don’t throw it away, but process it into chickweed pesto and other goodies.

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Other nitrogen-loving wild plants include burdock ragwort, sharp buttercup (also known as buttercup), field bindweed, shepherd’s purse, purple deadnettle, white deadnettle, and black nightshade. A nitrogen-rich soil is a good place for high- and medium-nutrient vegetables. To provide other important nutrients such as phosphorus, potassium and magnesium, the soil can be amended with mature compost and banana peels. The leaching of the soil is counteracted by green manuring after harvest.

The pungent stonecrop, which can be recognized by its fleshy leaves and bright yellow flowers, is a plant that grows in soil that is poor in nitrogen and often dry. It likes to grow as a pioneer plant in fallow areas and along railroad embankments, in wall cracks, and in dry woods. Where wall pepper grows, few nutrients are found, especially little nitrogen.

Nutrient-poor soils are also colonized by daisies, meadowfoam, and wild carrot.

To enrich such soil with nutrients, you can undermine mature compost soil. If the soil is to be prepared for the next season already in autumn, immature fresh compost is also suitable, which attracts earthworms and microorganisms. They loosen the soil and provide nutrient-rich humus. Autumn green manuring is also recommended. For Mediterranean herbs and other plants that prefer nutrient-poor substrates, on the other hand, the soil can be used without further fertilization.

Field horsetail and coltsfoot: loamy soil

Coltsfoot also indicates heavy soil and moisture to waterlogging. Other plants that need loamy soil are field mint, broadleaf plantain and goose cinquefoil. To prepare the soil for other plants, it can be dug up or loosened with a cultivator and sand and compost incorporated. Earthworms attracted to the compost also loosen the soil structure. Crops that tolerate loamy soil and moisture well include watercress, ivy, funkias and ferns. Sorrel and bracken: acid soil If you find a lot of sorrel in your garden, you have acid soil. Before you pull out the plants, consider leaving some of it. In fact, sorrel has many uses in cooking, medicinal purposes and in the home.

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The bracken also indicates an acidic soil. Other wild plants that signal an acidic substrate include heather and various mosses. An acidic soil can be improved by sprinkling baking soda. By watering, it spreads through the soil and neutralizes the acidity. Eggshells in compost also make the soil less acidic with their lime content. Instead of taking the acidity out of the soil, you can also cultivate suitable plants, for example blueberries, quince, kiwi and arnica.

Field bindweed and field mustard: alkaline soil An alkaline soil, usually very rich in lime, is present when field bindweed and field mustard grow. Common kidney vetch also prefers an alkaline soil, as does hare clover. Coffee grounds and conifer soil can lower the pH of the soil. Grape pomace, a by-product of wine pressing, can also be used. It’s best to ask a local winemaker about it. Oak leaves and tree needles provide more acidity in the soil when used as mulch. Mulching also prevents the soil from drying out or unwanted weeds from taking over.

Herbs such as rosemary, thyme or sage do well not only with nutrient-poor but also with calcareous soils. Lovage requires more nutrients, but also loves a calcareous soil.



  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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