Help your lawn thrive with these effective treatments for unwanted weeds.
Caring for a grass lawn can sometimes seem like a losing battle. No sooner have you fertilized and tended your lawn for the spring, when dandelions and other weeds start popping up everywhere. Yet science has proven again and again that common commercial herbicides aren’t safe—for pets, wildlife, and people. Where does that leave you?
To tackle weeds organically, you need to think differently. Understanding how weeds and their controls work is the first step to minimizing their presence. Creating an environment where your lawn can thrive will support getting rid of weeds for the long-term.
What makes a product organic?
Most of us know that organic growing means avoiding synthetic fertilizers, pesticides and herbicides. But what products can help us do this effectively? In the United States, the Organic Materials Review Institute (OMRI) reviews ingredients and product manufacturing to compile a list of products suitable for use in organic gardening. If you’re buying a commercially prepared, organic weed killer and you want to be certain it’s safe, look for the “OMRI-listed” label. You can also search products or ingredients on the OMRI website.
How do weed killers work?
Weed killers act on plants to prevent them from performing different life processes needed to survive. Most fall into one of two categories: pre-emergent and post-emergent.
Pre-emergent
Pre-emergent weed killers stop plants from sprouting and taking hold in the soil. They must be applied to the soil before germination takes place. Since seeds may sprout over a period of weeks, pre-emergent herbicides may need to be applied more than once in a season.
Post-emergent
Some weed killers work by damaging the cell wall or waxy cuticle of plants, leading them to dry out and die. These are known as post-emergent, because they act after the plant has already emerged from the soil and started to grow. Most post-emergent organic weed killers have one or more of the following as their key ingredient:
- Acetic acid
- Fatty acids
- D-limonene (orange oil)
- Other essential oils
The following organic weed killers have proven effective in different situations.
1. Corn gluten
Corn gluten is a pre-emergent herbicide that works on germinating plants to stop them from sprouting. It’s primarily made up of a natural protein from the endosperm of the corn kernel and is a by-product of ethanol manufacturing.
Corn gluten will stop new weeds from germinating in your lawn, but it must be applied early in the spring, before weeds emerge. Once applied, it will keep working for up to six weeks. If you are planting a new lawn or overseeding bare patches in your lawn, be sure to apply corn gluten at least six weeks before your grass seed. Corn gluten isn’t selective, and will stop grass seed from germinating, too.
Like other manufactured garden meals, corn gluten also makes an excellent fertilizer thanks to its high concentration of nitrogen. Given this quality, it’s important to apply corn gluten at the right time of year for weed control. When applied too late, corn gluten can feed the weeds instead of killing them.
2. Horticultural vinegar
Vinegar has long been a staple ingredient in homemade weed killers because of the quick damage it causes plants. At regular concentrations (4 to 5% acetic acid), household vinegar has been proven effective when used on young weeds. Made specifically for gardening, horticultural vinegar contains higher concentrations of acetic acid (20 to 30%) than household vinegars, so it compounds the damage.
While this concentration of vinegar will affect most plants, some studies indicate it’s more effective on broad leaf plants than on grasses. It’s also known to be more useful on immature seedlings than mature weeds. More recent information suggests that horticultural vinegar is most effective when used in dry climates (e.g. Texas, Arizona, California) or on a bright, sunny day when the soil is dry.
Use horticultural vinegar as a spot treatment on lawns as soon as weeds emerge. It’s most effective within two weeks of germination. Mixing with a surfactant like liquid dish soap will help the vinegar adhere to the plant. In many cases, surrounding lawn grasses will grow back after a brief setback. In others, you’ll need to reseed treated portions of your lawn. Avoid applying near aluminum or iron gates or fences and around masonry surfaces that may react or suffer from the acid content.
3. Burnout
If you’re looking for a safe, non-toxic solution to killing weeds where vinegar fails, consider this commercial preparation of Burnout. The main ingredients are citric acid (24%) and clove oil (8%), which make a lethal combination for weeds. Dandelions, thistles, pigweed, moss, morning glory, ragweed, clover, quack grass and more will wither and die when sprayed with a solution of water and Burnout. Taproots may require two treatments, but you’ll see results in a few hours. Plus, it smells nice!
You can replant an area treated with Burnout within 24 hours, because the preparation quickly breaks down in the soil. It’s also safe around pets. Keep in mind that Burnout isn’t selective and will kill grass, too. Use for spot treatment only on lawns.
4. Citrus Oil
Citrus oil (also known as D-limonene) is the active ingredient in many eco-friendly household cleaners thanks to its ability to break down grease and grime. This same ability works well on weeds, destroying the waxy coating that helps plants retain moisture. Made from the main ingredient found in the essential oils of citrus rinds, citrus oil makes an effective organic weed killer when diluted with compatible ingredients.
DIY preparations of straight D-limonene and water can be costly, but many people have found mixing a citrus-oil based cleanser (like CitraSolv) with household vinegar, water and dish soap works very effectively. Here’s one version of that simple recipe used for targeting dandelions.
Like other preparations above, spot treat your lawn as early in the season as possible. Be prepared to overseed areas around targeted weeds.
Tips for using organic weed killers
Just because a product is suitable for organic growing, that doesn’t mean it won’t cause harm. Consider the following suggestions to make sure you get the most from your products and stay safe at the same time.
- Treat problem weeds when they are young: two to five leaves only.
- Double-treat more mature weeds, especially those with established roots.
- Be sure to spray the entire plant and all growing points.
- Read the safety precautions on all products. Protect yourself with gloves.
- Avoid using salt, which can persist in the soil and prevent your grass from recovering quickly.
Other solutions for organic weed control
Post-emergent weed treatments won’t prevent future weeds from sprouting in your lawn. However, there are other ways to tackle weeds over the long term.
Prevent weeds from taking hold
A proliferation of weeds in your lawn is usually a sign your yard needs some tending. Know the reasons behind your weed problem and treat your soil accordingly. Once you have, mow your lawn on the highest setting your lawnmower will allow. This will help your turf develop deep roots and outcompete most weeds. Overseed yearly to keep weeds from taking hold.
Minimize your lawn
Having more beds dedicated to trees and shrubs can lessen the work involved in maintaining your lawn. Adding flowering or fruit trees to your landscape can also increase your enjoyment of your yard—and your harvest. Read more ideas for reducing your lawn size.
Consider lawn alternatives
Lawns made from a single grass species aren’t natural and are a lot of work to maintain. Ground covers and micro-clovers or micro-clover blends are available to help you keep the green look with less work. If you love your lawn, consider sowing low maintenance grass blends that support wildlife, especially pollinators. You’ll save time and money.
Related: How to Grow a Microclover Lawn
Treat large areas
If tenacious weeds colonize large patches of your lawn, consider treating the entire area by solarizing, smothering, or torching. These methods will bring you back to square one by destroying everything in the affected area, but they can help you get a handle on a large problem—with minimal work. For more information, read How to Get Rid of Weeds Naturally.
Thinking differently for a beautiful backyard
We can’t tackle the weed problem using old ideas. In many cases, targeted, organic weed killers will spot treat the problem and prevent it from recurring. In others, we need to think holistically about the ecosystem supporting our lawn and give it everything it needs to thrive.