Weeds: What they tell us about the soil

We established that, though weeds are often unwanted and can compete with your crop for nutrients and water, they can have multiple uses. One of the amazing things about weeds is that they tell us about the health of the soil. The weeds that are growing on our soil can indicate pH levels, drainage capacity, and amount of compaction in the soil. "Weeds grow in soils that are minerally deficient, bringing the minerals from within the soil up to the surface" (Palmer, 91). Weeds have the power to change the soil they are growing in over time and can tell us what is happening below the surface.



First, it is important to have an accurate way to identify weeds. In North Carolina, we have a guide published by NC State. There are apps that are helpful when identifying plants. Chime in if you have one you love. I like to use the Google lens on photos I take to help me identify plants. I also appreciate my local library as a resource for books on weeds. I have checked out and found helpful Weeds of the South, ed. by Charles T. Bryson and Michael S. DeFelice. Other books that have been useful to me in my search on weeds are The Regenerative Grower'sGuide to Garden Amendments by Nigel Palmer, Weeds and What They Tell Us by Ehrenfried Pfeiffer and Weeds: In Defense of Nature's Most Unloved Plants.



In an effort to figure out what weeds are growing on my farm and what they indicate, I have photographed and cataloged the main weeds I found growing on the farm. Of course, there are many more; but these ten weeds give me a good idea of the conditions of the soil and what is happening.



1--Black Nightshade is a particularly nasty weed with spiny stems. It grows in one section of my farm. It is a "typical weed in gardens and potato fields. They indicate a soil used up with excessive potato cropping and cultivation, a soil that is too loose" (Pfeiffer). While I have not grown potatoes where it is growing, it indicates to me that there was excessive cultivation where it is growing.


2--Dandelions are dynamic weeds. Pfeiffer defines a dynamic weed as "those which influence their surroundings in a specific way, so that other plants change their properties, or that a soil changes its character" (85). Dandelions transport minerals like calcium through their long taproot to the surface. Earthworms love dandelions, and the plants help to change the mineral deficiencies in the area in which it is growing.


3--Crabgrass seeds can lay dormant for 30+ years. As much as you pull it out, it can come back next year. It grows in compacted soil and will take over areas that are not properly mulched or already growing a crop.


4--Spurge "Many of the spurge family have a preference for dry, light, sandy soils, but spread out in yards, gardens, pastures, and other good land when given a chance" (Pfeiffer, 52). Thankfully, I have found spurge easy to pull out of the ground.


5--Virginia Copperleaf is the most prolific weed on the farm. It grows in beds, on pathways, and anywhere in between. It can be found in areas that have been cultivated or disturbed.



1--Pigweed is drought resistant and has seeds that can "remain inert for decades" (Pfeiffer). It thrives in areas that have been disturbed for cultivation. This weed grows in heavy clay soils but can also indicate soggy soil with poor drainage.


2--Nutsedge grows in wet areas with poor drainage. It spreads through rhizomes underground. I try to pull it out as soon as I see it in order to get the "nutlets" out of the ground.


3--Ladysthumb can grow in many different settings, including in the midst of crops and in meadows. "It indicates a slight acidity [in the soil], caused by insufficient surface drainage of the soil and lack of air" (Pfeiffer, 35).


4--Green carpetweed forms a mat on the pathways of my farm and "thrives in lighter, sandy soils" (Pfeiffer, 50). It has been easy to pull.


5--Plantain is growing prolifically in the living pathways of my farm. "They increase when standing moisture in the surface layers hardens the soil, but this indicates neither good nor bad soil, just that they like to be near it" (Pfeiffer, 48). They tend to grow in heavy clay and compacted soils.


The good news is that I was able to rid the above path and beds of the weeds shown this last weekend by pulling them out by hand. The bad news is that more will be back. I will apply mulch to the pathway and compost to the beds to help stop the spread of more weeds, but it is a constant struggle. I am thankful to learn more about the health of the soil at the farm and what may be needed for future growing seasons. I am not an expert on weeds and welcome any thoughts, observations, or comments on the subject. Thanks for reading!