What weeds tell us
Weeds can be used as indicators of soil conditions and as environmental indicators. You can then use this information to help create the best possible conditions for lawns and your turf grass
Weeds as indicators of wet soil conditions.
Plants like cat-tails, bulrushes (Cumbungi), and sedges show wet soils.
- Yellow Nutsedge.
- Common Purslane.
- Scarlet Pimpernell
- Oxalis sp
- Mosses and
Weeds and what they tell us about soil fertility.
Indicators of poor soil
- White Clover shows low fertility soil. It is a nitrogen-fixing plant that thrives in low-nutrient soils.
- Black Medic thrives in low-nutrient soils.
- The presence of redroot pigweed means that the Fe-Mn ratio is out of balance.
- Summergrass shows low levels of Ca and P and high levels of Mg and K.
- Dandelions show low Ca and very high levels of K.
- Oxalis sp shows low levels of Ca, and high levels of Mg.
Indicators of rich soil
- Stinging Nettles prefer nitrogen-rich soils.
- Chickweed shows nitrogen-rich soil. It also indicates very low Ca and P levels and very high K and Na levels.
- Chicory favours high nitrogen soils and so do lambs quarters
- Knapweed shows high soil K.
- Both mustard and purslane indicate high P levels.
- Shepherds purse
- Canada thistle
Indicator weeds for disturbed soils.
Weeds that indicate disturbed soils, include fireweed.
- Common Ragweed
- Shepherd’s Purse
- Field Thistle
- Japanese Knotweed
- Red root Pigweed
- Prickly Lettuce
- Wild Mustard and
Certain plants, such as mosses and lichens, are useful bioindicators of air quality and pollution. For instance, lichens are sensitive to air pollution.
Indicators of Soil pH.
Some weeds prefer acidic or alkaline soils. For example, mossy stonecrop (Sedum acre) grows well in acidic soils. In contrast, alkali grass funnily enough loves alkaline soils.
Acid soils (low pH)
- Velvet weed.
- Ox-eye daisies.
- Pearly everlasting.
- Sheep sorrel.
- Wild radish and
- and prostrate knotweed.
Alkali soils (high pH)
- Wild mustard and
- Black medic
- Broadleaf plantain prefers compact soil
- Ground Ivy.
- Crowsfoot is found on compact sports turf in warm-season grasses.
- Burdock has deep tap roots and likes compact soil.
- Knotweed is an excellent indicator of compaction.
- Inkweed will grow in heavy clay or compact soil.
After Graduating from Newcastle University with an Hons Degree in Soil Science in 1988, Jerry then worked for the Sports Turf Research Institute (STRI) before emigrating to Australia in 1993.
He followed this by gaining a Grad Dip in Business Managment from UTS and has worked in a number of managment roles for companies as diverse as Samsung Australia, Arthur Yates and Paton Fertilizers.
He has always had a strong affinity with the Australian sports turf industry and as a result he established Gilba Solutions in 1993. Jerry has written over 100 articles and two books on a wide range of topics such as Turf Pesticides and Nutrition which have been published in Australia and overseas.