Weed Suppression

An image of weed suppression techniques being applied to a garden.

Weed pressure in the garden can be daunting. Successful weed management in organic agriculture is a challenge that requires patience, preventative measures, dedication, and a commitment to following through with the systems put into place.

By Crystal Stevens

[This article was first published in The Gateway Gardener June 2018 issue.]

Weed pressure in the garden can be daunting. Successful weed management in organic agriculture is a challenge that requires patience, preventative measures, dedication, and a commitment to following through with the systems put into place. Weed seeds germinate quickly, causing an influx of weed growth during spring and summer. Weed management strategies are crucial for crop integrity, to help decrease pests and diseases, and to decrease the potential for pathogens.

Luckily, there are several techniques that can prevent the potential for weeds to overtake crops. EarthDance Organic Farm School has implemented a myriad of tried and true methods of soil building, mulching, and innovative methods of weed suppression to maximize crop yields and vitality therefore increasing profits.

No-Till. The no-till method creates living healthy soil in which microbes, beneficial bacteria, and fungi are provided an environment to carry out their intrinsic functions, allowing them to complete the process of nutrient absorption, decomposition, and in turn building healthy soils.

Adding clean, weed-free soil to garden beds can maximize the long-term health of soil, reducing the reliance on tillage.  Maintaining the permanent raised beds is important. They should be weeded regularly during the first few months.

Mowing. When facing large weeds initially, it is best to mow those first. It is crucial to not let weeds go to seed.

Start with Transplants.Transplants are often more successful in an organic farm setting. First, they are off to a great start as their roots are established before they go in the ground. They achieve canopy quickly meaning that they will cover the soil, shading out the weed seeds.

Add Compost. Heavy compost is a great way to use stacking functions, feeding the plants, adding nutrients to the soil, moisture retention, and weed suppression.  Adding several inches of weed-free compost on your existing bed is not only wonderful for the soil but can smother out the weed seeds buried below. 

Occultation. Occultation is a weed suppression method which is done by smothering the weeds using a thick black silage tarp. Occultation can be done throughout the growing season and is most successful when left for 3-4 weeks.

Solarization. Solarization involves covering the soil with clear plastic for 6-8 weeks in order to kill soil pests.  According to Beth Hanson in an article published in Rodale’s Organic Life Magazine,  “Solarization involves concentrating the sun’s energy in the top 12 to 18 inches. The heat trapped below the plastic can reach highs of 140°F in the top 6 inches, killing weed seeds, insects, nematodes, and many fungal and bacterial pathogens, including those that cause verticillium wilt, fusarium wilt, potato scab, damping off, crown gall disease, and phytophthora root rot. The beneficial effects from solarization are greatest near the soil surface and decrease with depth.”  

Cover Crops. Cover crops are a cost-effective way to add soil amendments and living mulch. They offer a protective layer for the soil,  help to loosen soil without tillage, allowing aeration, and water absorption. Cover crops increase soil health and diversity, water retention, soil organic matter, and nutrient uptake. Cover crops also help to prevent soil erosion. Some common cover crops include red and white clover, oats, mustards, tillage radishes sorghum-sudangrass, wheat, winter rye, buckwheat, cowpeas, barley, hairy vetch, and field peas.

Landscape Fabric. The use of landscape fabric offers a long-term strategy for perennial plantings, such as permaculture berm and guild plantings. Biodegradable plastic is another effective yet expensive way to suppress weeds. Though it is biodegradable, it takes years to break down fully. Another downside is that bits of plastic will start to accumulate as it breaks down. Non-biodegradable plastic is effective, but also expensive, and is not environmentally friendly. The plastic goes to the landfill. 

Sheet mulching, heavy mulching, mulched pathways and living pathways are other methods of suppressing weeds that were discussed in the May issue.

Weeding requires regular observation and attention. The optimal time to weed is when a weed seedling is less than an inch tall, even better, when they first sprout.  A tine weeder rake and a wire weeder are best used when weeds are at their white thread stage—the root looks like a white thread when pulled up.