The species of weeds invading your farm / nursery / garden can tell you a lot about the soil conditions. This is because each weed species thrives because it is better suited to the conditions than your cultivated plants. Many weeds are termed ‘indicator weeds’ which tell you that one particular feature is dominating your soil. An non-exhaustive list includes:
Wet/waterlogged soils: spore-producing plants, especially horsetails (Equisetum), bracken (Pteridium aquilinum), and mosses thrive in these conditions. Especially if it is also shaded. Plantains (Plantago) and creeping buttercup (Ranunculus repens) in turf, and redshank (Persicaria maculosa) and pale persicaria (Polygonum lapathifolium) in field crops / vegetable plot.
Compacted soils: rough meadow grass (Poa trivialis) and bromes (Bromus). You will often see pineapple weed (Matricaria discoidea) next to gates on diary farms where the cattle have compacted the soil around the gate entrance.
Sandy soils: common storks-bill (Erodium cicutarium) and bugloss (Anchusa arvensis).
Good fertility: ivy leaved speedwell (Veronica hederifolia), creeping thistle (Cirsium arvense), dead nettles, broadleaf dock (Rumex obtusifolius), cleavers (Galium aparine), chickweed (Stellaria media) and fumitory (Fumaria officinalis).
High phosphorus: stinging nettles (Urtica dioica). In fact nettles can be signs of human habitation on land that hasn’t been cultivated for centuries, due to the excess phosphorus tied up in the soil from human waste!
Low nitrogen: nitrogen-fixing legumes, particularly medics (Medicago) and clover (Trifolium), as well as black nightshade (Solanum nigrum).
Alkali soils: shepherd’s needle (Scandix pecten–veneris), onion couch (Arrhenatherum elatius), and weeds related to Brassica, particularly charlock (Sinapis arvensis) and shepherd’s purse (Capsella bursa–pastoris).
Pineapple weed (Matricaria discoidea): a common sight around farm gates on diary farms. The cattle compact the soil around the gate and this leads to the perfect conditions for this chamomile relative to thrive.
So if you are struggling to control one of these species, perhaps consider tackling the underlying reason for its presence, rather than reaching for the herbicide (weedkiller) straight away. For example, if you have Perennial sow thistle in clay soils, consider using Liquid Gypsum to open the soil structure up. Or if you have a garden lawn dominated in medic and clover, perhaps add some nitrogen fertiliser.
For more information on any of these topics, feel free to contact our technical team.
