Indicator plants: what are they & what can they tell us?

Edward

With a passion for growing installed at an early age, I have always been happiest outdoors in nature. After training as a professional gardener and horticultural therapist, I currently run horticultural therapy and community kitchen gardens in the UK, helping others access the many physical and mental health benefits of growing vegetables, fruit and plants.

Favourite fruit: apples and pears
Favourite vegetable: asparagus

Along with doing a soil test, you can get an indication of the soil’s nutrients and type from what plants naturally grow there. Learn all about indicator plants and their uses.

Plants growing naturally together — Indicator plants can help analyse the soil type [Photo: AliaksaB/ Shutterstock.com]

Indicator plants can be helpful in a quick analysis of the soil. Read on to discover the theory behind indicator plants, with some examples of the most commonly used soil indicator plants.

Contents

What are indicator plants?
What do indicator plants tell us?
An overview of important indicator plants

What are indicator plants?

If you are wondering what indicator plants are, they are simply naturally growing plants that can suggest the type of soil and its quality by their existence. For example, if a few or more types of nutrient-hungry plants are growing, you could assume that the soil they are growing on is rich and fertile.

Indicator plants cannot give an exact analysis like a soil test, but if several species are present, they can give a good indication of the soil’s properties.

Stinging nettles growing naturally — Stinging nettles can indicate that the soil is rich in nutrients [Photo: Orest lyzhechka/ Shutterstock.com]

What do indicator plants tell us?

Indicator plants can supply a surprisingly large amount of information about the soil they are growing in. Not only can they indicate nutrient and moisture levels, but the pH of the soil as well. For instance, if you identify ericaceous-loving plants like foxgloves (Digitalis purpurea), rhododendrons or azaleas (Rhododendron spec.) growing naturally, you can be pretty sure that the soil is acidic.

Here is a list of soil attributes that indicator plants can help identify:

Nutrient-poor soils
Nutrient-rich soils
High nitrogen content
Alkaline soils/high pH
Acidic soils/low pH
High water content
Lack of moisture
Light and sandy soil
Heavy or compacted ground

Mare’s tail growing in soil — Mare’s tail (Equisetum arvense) can indicate that the soil is damp and low in nutrients [Photo: Manfred Ruckszio/ Shutterstock.com]

An overview of important indicator plants

Daisies (Bellis perennis) and buttercups (Ranunculus) are perhaps two of the most commonly known indicator plants. Here is a table of other plants that can be used as indicators and the soil’s characteristics that they imply:

Indicator plants for poor soils	Field horsetail (Equisetum arvense), ice plant (Hylotelephium), lavender (Lavandula), ox-eye daisy (Leucanthemum vulgare), salad burnet (Sanguisorba minor)
Indicator plants for nutrient-rich soil	Bramble (Rubus fruticosus), chickweed (Stellaria media), dandelion (Taraxacum officinale), dead-nettle (Lamium), garlic mustard (Alliaria petiolata), stinging nettle (Urtica)
Indicator plants for nitrogen-rich soil	Cow parsley (Anthriscus sylvestris), dandelion, docks (Rumex), ground elder (Aegopodium podagraria), speedwell (Veronica), stinging nettle
Indicator plants for chalk or limestone soil	Betony (Betonica officinalis), bugloss (Echium vulgare), docks, meadow cranesbill (Geranium pratense), meadow clary (Salvia pratensis), salad burnet, toadflax (Linaria)
Indicator plants for acidic soil	Bracken (Pteridium aquilinum), corn chamomile (Anthemis arvensis), daisies, heather (Calluna vulgaris), mat grass (Nardus stricta), speedwell, wood sorrel (Oxalis)
Indicator plants for high water content	Butterbur (Petasites hybridus), creeping buttercup (Ranunculus repens), lesser celandine (Ficaria verna subsp. verna), mare’s tail, marsh marigold (Caltha palustris)
Indicator plants for dry soil	Bugloss, campion (Silene), Dyer’s chamomile (Anthemis tinctoria), ice plant, kidney vetch (Anthyllis vulneraria), ribwort plantain (Plantago lanceolata), spurge (Euphorbia), thyme (Thymus)
Indicator plants for light and sandy soils	Bird’s foot (Ornithopus perpusillus), chickweed, common knapweed (Centaurea nigra), mullein (Verbascum), spurge, wild carrot (Daucus carota), yarrow (Achillea)
Indicator plants for heavy, compacted soils	Creeping buttercup, creeping thistle (Cirsium arvense), dandelion, greater plantain (Plantago major), mare’s tail, silverweed (Argentina anserina)

Large dock weed plant growing — Dock weeds can indicate that the soil is high in nitrogen [Photo: Kazakov Maksim/ Shutterstock.com]

Although indicator plants can be helpful in analysing the soil, some are also considered a weed. Learn more about weeding and what are the best tools available for it in our separate article.