What Weeds Tell Us About Soil Conditions

Weeding is likely everyone’s least-favorite garden chore. It’s time consuming and it seems unending. While there are some steps we can take to help keep weeds out of our gardens, the reality is that weeds are just part of the process and will appear in most gardens and lawns from time to time. But what if we told you that weeds could be useful? As it turns out, weeds can tell us a great deal about soil conditions. This may in turn be helpful in learning about the current status of your soil and what you need to do to improve it. So let’s dig in and learn what weeds tell us about soil conditions, and how we can make use of that information.

What is a Weed?

Let’s start with a quick definition—what is a weed? As far as we can tell, the only real definition of a weed is “a plant growing where you don’t want it”. We should point out that this is different from an invasive plant, which is an introduced, non-native species that takes over a natural space to the detriment of native plants or human health. While this article is officially about “weeds” we’ll be using other native plants as examples as well.

Weeds as Bioindicators

While weeds may not be the plants that we want in our gardens, they may function as bioindicators—organisms which provide clues as to the overall health of the ecosystem in which they’re found. While the science of bioindicators can be complex, with a bit of understanding we can learn to “read” the weeds and wild plants found in our yards and gardens and thus gather clues about soil conditions.

So what do weeds tell us about the soil they live in? That depends on the weed—all plants have a set of conditions they need to thrive, and a healthy population of a given plant suggests that those conditions are in place. For example, wet or saturated soils may host populations of jewelweed, dock, yellow nutsedge, horsetail, ground ivy, pitcher plants, cattail, or speedwells. Dry soils may be home to purslane, prostrate spurge, hawkweed, carpetweed, yarrow, sheep sorrel, prickly pear, or yucca. Soil with a poor nutrient content or compacted soil conditions are often covered with mullein, knotweed, dandelions, bindweed, or crabgrass. Rich, well-fed soils however might showcase chickweed, chicory, common groundsel, henbit, or knapweed. Careful observation can reveal which nutrients are either abundant or depleted, or may reveal your soil pH. We still think it is best to have your soil tested if possible—your county extension office may do that for free or for a nominal fee.

What to Do With Bioindicator Weeds

So now that we know what our weeds may be telling us, what do we do with that information? There are several possible approaches we can take to addressing what weeds tell us about our soil. Which one we choose depends on our space, our resources, and our goals.

One possible approach is to correct the problem. In some cases—saturated soil or poor nutrition in particular—that may be the preferred approach. We can build in drainage, loosen the soil, or apply fertilizer or compost as needed. Likewise, with overly dry soil we may consider irrigation and watering options. For issues localized to one particular part of our yard or garden, these approaches may be effective and may even prevent further problems later on.

Alternately, if the soil conditions are endemic to our geography or climate, we may choose to embrace them by planting native plants, or plants that are water-loving or which thrive in dry conditions. Even if you’re improving your soil, garden, or lawn, you may consider preserving some of the native conditions and native plants if space permits.  Gardening is always a balance between improving conditions and working with nature, so we suggest considering both when addressing your soil conditions.