5 Best Weed Killers for Lawns, Driveways & Overgrown Areas

How Do Weed Killers Work?

Shepherd’s Purse, Lamb’s Quarters, Buckhorn Plantain…

No this isn’t a pretentious menu you’re reading, it’s a list of troublesome weeds that love squatting in your garden each year!

So if you’re like me, and the thought of picking them out one-by-one is enough to make you want to move into a high-rise flat, you’re going to need a the best weed killer on the market.

Weed killers, well, kill your weeds. However, there are several different types on the market, and they all work in different ways. For instance, systemic weed killers are absorbed into the plant itself, and then travel down the root, killing the plant from the inside out. Residual weed killers are applied to the soil itself, and prevent weed seeds from germinating.

Contact weed killers are herbicides that kill on contact, and will often affect all plant species (not just weeds). Selective weed killers are contact formulations, but generally target broadleaf weeds only and are often applied to an entire lawn.

In general, the actual method of action in a weed killer could be one (or more) of several different options.

Stopping Photosynthesis: Plants need light in order to survive and create food, a process known as photosynthesis. Some weed killers work by stopping the plants ability to photosynthesise. Deprived of this food source, the plant essentially starves to death.

Stopping Protein Production: Protein production is an essential element of plant growth and health. Some weed killers stop a plant from being able to produce proteins, which ultimately causes the plant to die. Glyphosate, the chemical you’ll find in Roundup weed killer, works in this way.

Hormones: Plants do have hormones, and those chemicals dictate growth. Some weed killers contain plant hormones (either natural of synthetic), such as 2,4-D (Trimec). When applied to the plant, the hormone is absorbed, and confuses the plant’s growth system. It eventually becomes deformed and then dies.

Note that different types of weed killers target various plants. Some are specifically designed to kill broadleaf weeds like dandelion, while others might target grasses. Yet others target all types of plants. There is also no such thing as a dog-friendly weed killer, at least not until the application has dried completely, so always keep pets and children away from treated areas during and immediately following the application of any weed killer. Check the safety precautions and application instructions on the bottle, as well.

Types of Weed Killers

Again, there are multiple types of weed killers on the market. Selective weed killers are usually safe for application on lawns, and will target only specific plant types. Non-selective weed killers will kill any plant with which they come in contact. It’s down to you to find the best weed killer for your needs.

Systemic weed killers are slower than others, but can kill even resistant plants like brambles and briars. Note that systemic weed killers are sometimes called industrial weed killers. Post-emergence weed killers are designed to be applied to the weed after sprouting, while pre-emergence weed killers are applied before growth begins.

Note that there are some “natural” weed killers on the market. For instance, corn gluten is one such product, and you’ll find it used in some selective, pre-emergent weed killers. Corn naturally secretes a chemical that makes other nearby plants die (fighting off competition). That chemical is found in heavy concentrations in corn gluten. However, it is generally not effective against regular lawn grasses, which is what makes corn gluten an excellent option for pre-emergent weed control in lawns.

Finally, there are industrial weed killers, also called “soil sterilisers”, that were once available on the market. While these are not usually sold any longer, they can sometimes be found. Soil sterilisers are not recommended for use, as they kill pretty much everything in the area, and can linger for years to come. They can also wash into other areas through rainwater runoff, find their way into streams and rivers, and eventually reach the ocean.

What’s in Weed Killers?

Weed killers use chemicals (herbicides) to control, limit and stop plant growth. The actual chemicals in the formulation can vary depending on the brand and the type of weed killer in question. Many are safe for application on other plants (selective) although you should always read the packaging before applying them to edible plants that you intend to consume.

Some products are also rated as being safe for pets and other animals (nontoxic formulations), but others are not. Again, always read the packaging material for safety information before you start spraying your plants.

It’s important to note that the chemicals in most weed killers are not as effective during warmer temperatures. This is not necessarily due to any shortcoming of the herbicide itself, but to how plants absorb moisture. Most plants absorb more moisture in the cool of the early morning, but stop when temperatures rise in the afternoon. So, for the best results, apply your weed killer early in the day.

All weed killers have the potential to be washed into other areas through rainwater runoff. Spraying during windy conditions can also cause the chemicals to spread to areas that you did not intend to treat, killing plants that you wanted to save.

Final Advice

As you can see, there are some excellent weed killers on the market. However, if you’d prefer to go a non-chemical route, there are also plenty of options. Mulching is an excellent way to smother weeds in flower beds and gardens while also ensuring better moisture retention in the soil. Hand tools can also make weeding a simpler matter, and you’ll find tools designed for use in vegetable gardens, flowerbeds and even in your lawn.

However, if you’re dealing with a serious invasion of weeds, chemical weed killers might be the only option. Always read the safety precautions and usage directions, and always wear protective clothing and gear when applying chemical weed killers.

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