by Marshall Grain Co.
How to Choose the Right Organic Weed Killer
People often bring us a weed they've dug out of their lawn and ask us what kind it is. They may have even already spent hours searching through online photographs of "weeds" trying to precisely identify the plant they've pulled.
What they really want to know is how to kill it. And that question is much easier to answer. For most purposes, there are really only 2 types of weeds: grassy weeds and broadleaf weeds.
Grassy or Broadleaf?
Grassy weeds include annual #Ryegrass, annual #Bluegrass, #Dallasgrass, #Johnsongrass, and #Crabgrass. Some grassy weeds grow in clumps while others spread out into a mat, but generally speaking they look similar to our beloved St. Augustine and Bermuda lawn grasses.
Broadleaf weeds include Dandelions, Aster, Groundsel, and White Clover. Some, like Dandelions, are annuals that form a single plant that lives for a single season and then dies, leaving behind seeds that will make up the next generation. Others, like Aster, are perennials that grow back from the root. They also drop seeds that grow into more Aster the following year.
When it comes to formulating weed killers, it's much easier to distinguish between a grassy plant and a broadleaf plant than it is to tell the difference between two grassy plants. In other words, it's much easier to make a product that kills plants different from your lawn than it is to make one that targets plants similar to your lawn. Weed killers are generally unable to make that distinction and so they will kill your lawn along with the grassy weeds. Then there are non-selective killers that can also harm your lawn if used incorrectly.
Not what you want!
The good news is that there are a growing number of organic options and they continue to improve in effectiveness.
Non-Selective Organic Herbicides
Non-selective weed killers are great for killing all the shoots that come up through the cracks in your sidewalk, between stepping stones, and other places where you just want to clean out unwanted growth. If you're careful, you can also use them in your lawn to spot spray weeds. Using a handheld squirt bottle or pump-up sprayer, hold it close to the target weed and saturate the plant thoroughly with the product.
One way to make sure you spray only the weed and not your grass is to place a toilet paper roll over the weed to be sprayed and use that to direct the flow of the product onto the weed.
Still one of the best non-selective weed killing choices is 20% (or 30%) Horticultural Vinegar. A strong acid, it reacts with sunlight to burn plants back to their roots. It also acidifies the soil, which helps kill alkaline-loving plants. Because it requires sunlight to be effective, it's not as effective in shaded areas, and it works better on younger, smaller weeds than on larger established plants. It also works better on broadleaf weeds than grassy ones. Make sure you thoroughly saturate the foliage of the plant as well as the soil around it.
You can improve the effectiveness of the product by adding an ounce of Orange Oil and a few drops of liquid dish soap. Orange Oil is also an herbicide (among other uses) while the soap helps make the mixture stick to the foliage of the plant. (Get the recipe.)
Horticultural Vinegar is also the fastest acting weed killer available. Most other products take up to 2 days to work. Vinegar kills within a couple of hours.
It's important to note that grocery store vinegar is not suitable for killing weeds. Consumable vinegars are only about 5% - 7% vinegar. (Any more than that would burn your mouth!) A dilution rate of less than 20% is not effective and in some cases can actually encourage plant growth. So make sure you buy Horticultural Grade vinegar that is at least 20% strength. Because it is such as strong acid, some states won't allow the sale of anything higher than 20% concentration. Fortunately, the State of Texas allows the sale of both 20% and 30% Horticultural Vinegar for garden (and other outdoor) uses. And of course, both are available at Marshall Grain Co.
Another non-selective option is Puregro's Weed Crush. Weed Crush is a relative newcomer to the organic weed control market, but has won the recommendation of local organic landscape expert, Howard Garrett, also known as "The Dirt Doctor."
Weed Crush is a general-purpose vegetation killer that knocks out both grasses and weeds. It acts through contact and protects the soil, flora, and fauna -- meaning it will not be toxic to humans or animals.
Since it is non-selective, take your toilet paper roll out with you and be careful not to damage your turf.
Broadleaf Weed Killers
There are quite a few highly-effective organic broadleaf weed control products available. Our recommendations include Pulverize Green weed killer for lawns. It's available as a spot spray or as a much easier to apply hose-end dispenser that can be broadcast over your entire lawn in one easy step. Be careful to choose the right formula. The company also makes a weed AND grass killer that should not be used on your lawn. They also make a brush a vine killer for poison ivy and other tough plants.
Grassy Weed Killers
So far we've mainly talked about easy-to-kill broadleaf weeds, but what about grassy weeds? As we mentioned earlier, it's much harder to come up with a product that will kill "bad" grass without harming your "good" grass. Luckily there is all-natural AgraLawn Crabgrass Killer. AgraLawn, which is also recommended by The Dirt Doctor, kills not only Crabrass but also #Basketgrass, #Chickweed, #Clover, and #Dollarweed without harming turf grasses such as St. Augustine, #Bermudagrass and #Zoysia. The active ingredient is Cinnamon.
When used properly, AgraLawn Crabgrass Killer causes very little reaction or yellowing to St. Augustine lawns. Applying during the a.m. hours while morning dew is present works best, or you can wet the affected area with a hose, irrigation or spray bottle. The product will change color from white to bright yellow to indicate adequate moisture has been applied. Results will become visible in 2 to 4 days.
All of the above products are "post-emergent" weed killers designed to get rid of existing weeds. But obviously it's to better to prevent weeds from cropping up in the first place. The two most important things you can do to discourage weeds is to 1) Maintain a healthy, organic lawn; and 2) Use Corn Gluten Meal as a pre-emergent herbicide.
A lush, healthy lawn will crowd out a majority of weeds because their seeds will not be able to penetrate through the grass down to the soil.
North Texas is notorious for its poor soils, which hamper plant growth and cause lawns to grow less vigorously. The more you can improve your soil with organic soil amendments and fertilizers, the better. Follow our recommended organic lawn maintenance program to improve your lawn. (See link below.) By improving your soil and regularly fertilizing, your lawn will grow in thicker and denser to help keep weeds out.
Corn Gluten Meal Pre-Emergent Herbicide
Keep in mind that the weeds you see today germinated several months ago. Tiny weed seeds can take 6 months or more to germinate and grow large enough to become visible in your lawn. You don't have to wait until they're established to deal with them. Kill them before they ever sprout with Corn Gluten Meal. When used regularly and correctly, it can significantly reduce the total number of weeds in your lawn and beds. Corn Gluten Meal should be applied at least twice a year -- once in the spring and once in the fall. Depending on the weather, more applications may be necessary.
For an in-depth discussion on how to care for your lawn organically, read our Ultimate Organic Lawn Care Guide. You can also refer to the printable Marshall Grain Lawn Care Guide below which includes the complete lawn maintenance schedule used by our own Organic Lawn Care Services team.
While your lawn may never be 100% weed free, following our suggested program and using the products discussed in this article will make your lawn care job much easier, while keeping your landscape organic.
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