Gardeners know that cultivated plants are adapted to certain conditions depending on the plant’s needs. That is why we use the phrase “right plant, right place.”
When it comes to weeds, just like all plants, the specific plant is associated with specific environmental conditions. Knowing which weeds thrive in which of these conditions can help with not only controlling the weeds through cultural practices, but also reveals underlying issues with the soil that is allowing the certain weeds to thrive. Improving the soil conditions can help mitigate the spread and growth of the weed in question but can also improve the health of the cultivated species one is growing.
Healthy soil is crucial for plants to flourish. There are several issues that arise in soil that can be detrimental to plant health.
Soil compaction is a problem in lawns and gardens alike. Proper soil will be half minerals and half water and air. As the soil becomes more compacted, water and air are pushed out, leading to poor drainage and poor root development. The soil becomes less aerated, which in turn inhibits root and invertebrate movement integral in soil health. This also impedes proper water filtration.
Another major issue, especially here in the Lowcountry, is water-logged soils. This creates areas that become anaerobic, or lacking oxygen, which is important to proper root development. Then there is the common complication of depleted soils, whether from heavy cropping or just nutrient leaching.
There are dozens of examples of weeds exposing soil trouble.
Crabgrass (Digitaria species) and goosegrass (Elusine indica) in the summer do well in compacted soils as well as drought-prone soils, while general turf grass will thin out.
Japanese stiltgrass (Microstegium vimineum) and poison ivy (Toxicodendron radicans) do well in low light areas where even the most tolerant turf will struggle.
Important weeds in the sedge family, such as yellow nutsedge (Cyperus esculentus) and green kyllinga (Kyllinga brevifolia), are often found in areas with compacted soil or waterlogged soils. This does not mean they are not found in other areas, but other plants struggle in these conditions while these weeds can thrive. This makes them important environmental markers.
Legumes such as black medic (Medicago lupulina) and white clover (Trifolium repens) also are great indicators of poor nutrient availability. Legumes can fix atmospheric nitrogen and can grow in soil that is lacking in such.
Dandelions (Taraxacum officinale) are a well-known soil health indicator in turf grass, as their presence can indicate a significant lack of available calcium in the soil as well as a lack of phosphorus, or even iron. An overabundance of broadleaf plantain (Plantago major) is a good indication of the soil’s overall lack of fertility.
While weeds are a nuisance in most gardens, they reveal problems in the soil. And by knowing these problems, we can moderate and reduce weeds through cultural practices.
Improving soil health through amendments and cover crops can reduce the weed pressure. Soil health is such an integral part of any garden that soil preservation is imperative.
Now the presence of any specific weed is not the perfect determination of a specific problem, but if weeds in general are thriving more than the intended plant, then they are a good indicator of problems within the soil itself. When it comes to soil compaction or poor drainage, pay attention when it rains and determine how long it takes to percolate into the soil.
Weeds are a sign that something needs to be adjusted, but the best way to know for sure is to have the soil tested. Knowing what is going on in the soil can go a long way to improving whatever type of garden you are trying to grow.
Whether it is turf or vegetables, soil health is important and can go a long way in avoiding spending too much time and money on fertilizers.
The best thing to do in any situation is to have the soil tested. For more detailed information regarding weeds and soil health, visit Clemson University Home and Garden Information Center at hgic.clemson.edu.