Reading Weeds to Identify Your Garden’s Needs

Bedded down for winter

After pulling weeds and tending to plants all summer, it’s tempting for a gardener like me to hang up the hoe as soon as the last bunch of kale is gathered and the last tomato is picked–or frost-bitten, as is often the case in Montana. Finally, a break from the daily maintenance of a 52-foot plot!

But before stowing away all of my implements for the winter, I have a few final tasks to tend to. In a plot like mine, sewn on soil that is far from ideal for planting, it is critical to take measures to improve the soil a little bit each year so that its clay-like, calcium-poor quality will gradually transform into a carbon-rich, nutrient-dense bed for my fruits and vegetables.

This past May I attended a soil seminar by international specialist Nicole Masters, who has been consulting with a local rancher in my area to improve the health of his grazing range. I gleaned numerous takeaways from Masters’ workshop, which focused on practices engineered to get carbon back into our soils and out of the atmosphere, where it contributes to global warming. Most of these practices must be implemented well in advance of planting in order to reap their benefits, making fall just as important a season for gardeners as spring and summer.

During her seminar, Masters discussed the critical role that carbon plays in retaining moisture and nutrients in our soil as well as the consequent decline in fertility that occurs when topsoils are mistreated, as they commonly are in industrial agricultural operations (not to mention the disruption caused by urban and suburban land uses). In the middle of the last century in Montana, where I live, soil carbon levels hovered around 20% whereas today those levels linger between just 1.5 and 2.5%, resulting in reduced moisture and nutrient content. No wonder we are not getting enough minerals such as magnesium in our systems for healthy sleep!

Masters shared numerous soil-building practices that can help reverse this trend such as minimizing tillage, herbicides, pesticides, and chemical fertilizers and replacing them instead with natural soil amendments such as organic compost, compost tea, cover crops, fish meal, manure, mulches, and lime, all of which provide food for the microorganisms that play a critical role in soil health as well as add the nutrients necessary for plant growth (man-made amendments simply furnish isolated minerals without feeding soil organisms). Much of this I already knew; I bed my garden down with leaf and grass clippings every fall (as shown in the photo above), underneath which I leave the remains of any plants I pulled up. The clippings and plant remains feed the earthworms and microorganisms beneath the surface throughout the winter. In the spring, I add a handful of organic compost along with each seed that I sow.

But one thing I DIDN’T know before attending Masters’ seminar was how to read the weeds in my yard to determine just what types of soil amendments I should be adding to my soil to correct its unique imbalances. According to Masters, every weed species has evolved to thrive in very specific soil conditions, a fact that can be a boon to gardeners rather than a bane. By identifying the weeds in our plots and determining the types of conditions that those weeds thrive in, we can learn a great deal about the types of soils we are dealing with.

As for me, the dandelions, Canada thistles, lambs quarters, and scouring rushes that populate my plot indicate that my soil is low in calcium and phosphorous and high in potassium and magnesium (most soils in eastern Montana actually have the opposite problem: they are too high in calcium and too low in magnesium). Note that just because a soil is high in a particular mineral doesn’t mean that the mineral is necessarily available for plants to absorb; without a healthy balance of soil organisms, minerals remain bound up in an unavailable form.

So how did I read my weeds? I purchased a publication Masters recommended entitled When Weeds Talk, by Jay L. McCaman. The text includes table after table detailing the conditions in which hundreds of species of weeds thrive (you can likely find similar information online). The downside to the publication is that it doesn’t include images, so I purchased a copy of Edible & Medicinal Plants of the Rockies, which has the pictures and descriptions I needed to identify my weeds.

To identify the weeds in your own yard, you can talk to neighbors and friends who have lived in your area for awhile; to other gardeners and farmers; and to extension agents from your state’s university system. If you don’t live near an extension office, you might be able to mail specimens of your weeds to the nearest extension office for identification, which may or may not entail a fee. Once you identify your weeds and figure out what they tell you about the nutrients (or lack thereof) in your soil, you can develop a plan appropriate for your own plot’s improvement.

After identifying your garden’s needs, I recommend doing a Google search for organic or natural soil amendments, making sure to include the specific nutrients you need in your search query. In the search results you’ll find options for purchasing amendments online as well as gardeners’ tips for making your own amendments at home. As for me, I discovered that saving up all of my eggshells throughout the summer, boiling them (to kill any potential salmonella), air-drying them, then crushing them and adding them to my soil in the fall will fix calcium back into my soil by spring (the microorganisms and earthworms need about three months to break the eggshells down and release the nutrients). I keep a jar next to my sink so that I can store my eggshells there after rinsing them out; once the jar is full, I boil the shells then dry them on a cookie sheet in the sun (you can do this in the oven as well). Once they’re dry, I crush them in my fists and add them to a tub full of crushed eggshells that I build up during the winter, spring, and summer.

In a few weeks, once nighttime frosts set in and my kale finally kicks the bucket, I’ll work the crushed eggshells into my soil and cover my bed with a layer of leaves and grass clippings to feed the earthworms and microorganisms that will work their magic throughout the winter to make my soil just a little bit better next spring than it was in springs past, thereby making my fruits and vegetables evermore nutrient dense.