Know your Garden Weeds

Discover the benefits of red clover, dandelion, burdock and more for improving your garden soil.

Burdock

Burdock's presence in the garden may mean that your soil needs more mineral content.

Photo by ArgenLant (iStock)

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Weeds are traditionally the bane of the gardener’s existence. The prevailing garden wisdom is that the weed is an interloper that will compete for water and nutrition, leaving our beautiful vegetables to wilt and die. The EPA estimates that in 2007, home gardeners in the United States used between 5 and 8 million pounds of glyphosate to eradicate weeds. That’s a lot of time and money spent fighting a battle with Mother Nature that is, at the very least, wasted time (not to mention that glyphosate is well-documented to be harmful to us).

What if I told you weeds could actually be here to help? One of the first things I learned as a gardener was that I am much more successful when I work with Mother Nature rather than against her. In that spirit, I began to research my weed enemies, and learned that weeds can be indicators of soil health.

In order to thrive, weeds require a certain nutrient profile in the soil. Some weeds feed off of a surplus of one nutrient that is created by the deficiency of another. This gives us plants that are capable of both mopping up surpluses and gathering small amounts of deficient nutrients and concentrating them in a given area.

If we fight these weeds by pulling and removing them, or spraying herbicides, the battle rages on. Until its nutrient profile changes, your garden will still be a great place for that particular weed to grow. But when we learn from the weed what the soil needs, we can address the underlying issue.

It became clear to me that if I could learn about my weeds and their talents, I could use them to do some of my gardening work for me. I could make adjustments to my fertilization plan, for instance, if I knew the presence of dandelion suggested that my soil was deficient in calcium. As I progressed, I even found ways to keep my garden looking neat and tidy by using the weeds themselves as green manures in a targeted way.

Here are a few weeds you should get to know if you would prefer to have a free workforce in your garden rather than enemy combatants. Learn to work with these plants, and you might just find yourself spending less time weeding and more time in the hammock watching the garden grow!

Burdock (Arctium lappa)

Burdock is probably best known for its Velcro-inspiring burrs. Instead, it should be known as hands-down one of the most effective plants for improving soil devoid of minerals. The deep roots of burdock can reach down about two feet, pulling buried nutrients up into the topsoil where they are accessible by shallow-rooted garden plants. Burdock is a biennial. In year one, the plant is just a rosette of leaves and the root extends down into the subsoil to pull nutrients. Burdock continues this work in its second year, producing a flower stalk and seeds while widening its path through the soil. At the end of the second year, the roots rot inside the new spaces they have created, releasing the nutrition they have stored, plus leaving new space open for air, water and soil workers such as worms to get in.

Work with this Weed: Burdock should be allowed to decompose in place. Provided the seeds are gathered before they have a chance to disperse, each plant that shows up in your flowerbeds will die of its own accord in the fall of the second year.

Read the Weed: If you’ve just got to remove your burdock, take a hint from its presence and add in some rock powder. Get a detailed soil test to know what minerals you are lacking and then fold them back in.

Chamomile (Matricaria chamomilla)

German chamomile is an annual that self-seeds along the surface of the soil. This makes it effective at breaking up crusty soils. Chamomile is more likely to show up as a weed where the soil is especially acidic. These annual plants grow from spring through the first light frosts and then fall back to the soil where their high levels of potassium and calcium enrich the topsoil. Stirring the whole plant into compost activates decomposition, a fact that has not escaped the notice of biodynamic farmers, who use this practice routinely.

Work with this Weed: Chamomile should be allowed to decompose in place. Harvest a handful whenever you are making a new batch of compost to add to the pile as an activator.

Read the Weed: If chamomile is taking over, its presence may be telling you to add some potassium and/or calcium fertilizer to the top layer of your garden. Great options are potassium sulfate, oyster shell lime or a high-calcium compost blend. Furthermore, it may be a great time to research methods that do away with a need to till constantly. Look into a broadfork!  >>

Red Clover (Trifolium pratense)

Red clover shows up in newly disturbed soils, such as those that have been recently tilled. Tilling disrupts mycorrhizal fungi relationships by physically breaking them apart and encourages a loss of nutrition as they are no longer available to bring nutrients to the root zone. Red clover is one of the best-known plants for fixing atmospheric nitrogen into a form usable in the soil by plants such as beans and peas. This process happens at the root zone, because of a symbiotic relationship with mycorrhizae. In red clover’s presence, mycorrhizae create networks of threads that move both macro- and micronutrients to where plant roots need them. Letting red clover grow will bring about the same result as buying a nitrogen-fixing inoculant, improving the nitrogen content in the surrounding soil for the benefit of neighboring plants.

Work with this Weed: Red clover may appear on its own, or you may plant it as a cover crop. The plants should be allowed to decompose in place.

Read the Weed: I find it difficult to replace exactly what the red clover plant can do for my garden, but if you can’t keep the weed, your best option is to add good compost and avoid tilling your soil.

Dandelion (Taraxacum officinale)

Americans have benefited greatly from this European import, though many people would disagree. Dandelion is a beneficial companion plant, breaking up hardpan, pulling up deeply buried nutrition (calcium especially) and creating channels for earthworms to move freely. As the dandelion roots loosen the soil, they also ensure that water can move freely, allowing toxic salt levels to leach downward and prevent unhealthy accumulation. Contrary to popular belief, the roots of dandelion do not compete with shallower root systems, as they are not feeding in the upper three feet of topsoil. It is only when the flower blooms that the plant begins to cause a negative effect, slowing growth in the plants nearby. Managed well, dandelion is a valuable asset to the garden.

Work with this Weed: Dandelion can be allowed to grow in the garden, but should be scrupulously dead-headed or simply harvested before it is allowed to turn into that familiar white puffball. Turning the leaves and roots back into the garden as mulch or via compost teas can be highly beneficial.

Read the Weed: If you can’t keep up with them, or just can’t abide them, learn from dandelion that your soil is packed too tightly. You might want to invest in a good soil test and look into adding some rock powders to bring in minerals and loosen things up, and you might also want to try a broadfork instead of a tiller in the rows.

Thistle (Cirsium spp., Carduus spp. and Silybum spp.)

In the Midwest, where I live, one of the most prolific weeds is thistle, because of the high clay content of our soils. As water lays on top of these hard soils, we end up with a crust on the surface and compressed hardpan below. Thistles tend to grow where potassium is lacking, pulling it up into their roots while they bust up the
hardpan layers.

Work with this Weed: If you cut off the top half of thistles after they’ve bloomed throughout the season, they will wither and die, preventing the spread of seeds and readying the plants to be turned back into the soil with all of their accumulated “green manure.” Alternatively, collect the seeds, then allow the plants to decompose in place.

Read the Weed: If you’ve got to pull the thistles, take a cue from them and consider adding some potassium fertilizer (potassium sulfate is a great option) to your garden. You might also look into the biodynamic technique called ashing. We’ve had great success burning our thistle and applying it in this particular way back onto the soil.


Want some more innovative uses for weeds? See Making Compost Tea!


Dawn Combs is an ethnobotanist and the co-owner of Mockingbird Meadows Farm, which has applied biodynamic principles for more than a decade. She is a frequent speaker at organic and biodynamic farming conferences and Mother Earth News Fairs around the country. Dawn is the author of Heal Local, 20 Essential Herbs for Do-it-Yourself Home Healthcare.


To explore this topic further, check out the books Weeds and What They Tell Us by Ehrenfried E. Pfeiffer; Weeds: Guardians of the Soil by Joseph A. Coannouer; A Manual of Weeds by Ada Georgia; and The Intelligent Gardener: Growing Nutrient Dense Food by Steve Solomon.