What Weeds Can Tell Us About Our Soil

Years ago I bought a little booklet that was titled, ‘Weeds And What They Tell’ and then bought the book ‘Weeds of the West’ to help me identify them.


It went no further except to help me figure out my invasive thistle problem. Thistle is often an indication of lack of copper or iron. If the soil is alkaline then the plants can’t uptake iron from it even though it might be available. I treat with sulfur, lots of it because our soil is super alkaline. The seeds are still there but they don’t grow or don’t in areas I’ve finally gotten enough acidity. I’ve also observed that thistle does not grow in my yard except where the soil has been disturbed, then it shoots up in thick patches. I don’t disturb anymore than I have to now.

Dandelions: love disturbed soil and their presence indicates poor soil that is low in calcium, but high in potassium.

With my north garden rather barren from neglect, I’ve decided I’d better lower the livestock numbers and concentrate on amending my soil. But what kind of soil do I have. I could choose to have it tested but that would be a pretty penny as I’ve got lots of areas where I’m growing trees, bushes, and gardens and I know in Wyoming your yard can be sand in one spot and clay or shell in another. I heard in a nearby town that people have acidic soil on one side of their yard and alkaline on another. So instead of opening my pocket book, I’m going to test my soil by a far less expensive route.


These are just the foothill of a much larger mountain range behind of which we sit on a hill on the east side.

Location: According to Soils of Wyoming site, we most likely have sandy soil because we are on the East side. Which means water and nutrients flow out quickly.  The site tells of topographical features in Wyoming and because of your location to them which likely soil type you have. It also mentions types of vegetation to look for as an indicator. Check for a similar site about the area you live in. It may be a good place to start.

There is also a simple soil test you can do of your own involving a jar, water, soil, and a small amount of salt.

Taproots: The length tells us a great deal. Deep taproots break up soils and eventually as they decompose, they create pathways for water and nutrients so that weaker root systems can thrive. If you have lots of weeds with deep taproots then your soil is either heavy clay or compacted. Weeds with hairnet root systems or clumping grasses are likely where the soil is loose and prone to erosion. That is why our mountains have lots of pine trees with large hair roots.

Dock and goldenrod: grow in wet, poorly drained soil.

Bindweed: grows in crusty or compact soil.

Knotweet: grows where the soil is compacted.

Mustard: grows in dry, sandy soil, high in phosphorus.


Yarrow: grows where the potassium and fertility are low and the soil is sandy and dry.

Because of our location to the mountain and that the yarrow plant grows in abundance around our home, I know that our soil is low in fertility because it is very sandy. Knowing what I’m dealing with allows me to amend the soil. The soil needs plenty of animal manure, green manure, leaves if I had them, and mulched to protect against water evaporation. It also tells me I need to water more often.

Nutrients:  We’ve mentioned this above but I want to emphasize it here. Plants tell you what nutrients your soil is high in and low in. For instance if your yards is abloom every spring with dandelions then your soil is poor and low in calcium, but high in potassium.

Crabgrass: grows where the soil has been depleted of nutrients and is low in calcium.

Fragile fern: grows in near-neutral, dry conditions.

Lamb’s .quarters: indicate rich soil, high in nitrogen.

Plantain: grows in compacted, sour soil with low fertility and often indicates heavy clay.

What is sour soil? It is a term once used to indicate acidic and may even smell sour when tilled. Sweet soil is alkaline or neutral. It seems like from the internet that most people deal with acidic soil problems but most of Wyoming is alkaline.


But you can’t take that as a blanket approach to dealing with your garden. Mullein grows in acidic soil with low fertility and it grew down the hill from us by the creek until a neighbor leased the property and grazed it heavily with his heifers. The manure left has moderated the soil and their hooves tilled it. I wish I’d taken a before and after picture as the once sorry looking property is now a flush haven. So I know there are patches of acidic soil nearby, just not on our property.

I’ll take our sandy soil over what we had, heavy, heavy clay, and yes, it does have some advantages. Root crops like beets, radishes and other tap-rooted vegetables perform better in it. That is they would as soon as I figure out what nutrient my soil is so lacking in. Herbs are also suppose to like sandy soils. If I can get enough

You can be sure this summer I’m going to be observe what naturally grows where in my yard. Then look up not only what it is but what it can tell me about the soil. That way I’ll know what ways I can more effectively amend my soil.


3 thoughts on “What Weeds Can Tell Us About Our Soil

  1. Valerie

    I’m sure you have seen the way to test your soil with baking soda and vinegar. I have heard that comfrey is an amazing mulch that will do great things for your soil. The best part is all you have to do is pick the leaves and lay it on your garden bed.


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