Everything You Need To Know About Weed Killers

Everything You Need To Know About Weed Killers

Have you noticed that your garden plants are struggling to reach their full potential? Are they withering away for no particular reason? If so, it may be that they are being overtaken by harmful weeds that are stunting their growth.

With this in mind, you may want to consider using weed killer to help your garden grow to its full potential. Weed control is extremely important if you want to have a beautiful garden all year round.

Weed control is also essential to healthy agriculture. In other words, it’s not just flowers and plants that can benefit from weed killers. You can also use these products to help your vegetable garden grow.

Weeds being pulled from the ground

But, with so many different weed killers now available to choose from, it can be difficult to choose the best one for your garden. With this in mind, we’ve created this comprehensive guide where you can find out more about what weeds are and how weed killers work.

We’ll also share some information on the history of weed killers, the difference between contact and systemic weed killers as well as highlight some important facts regarding safety for you, your loved ones, and your pets.

Lastly, we’ll tell you the difference between weed preventers and weed killers, as well as tell you how to apply weed killer and some top tips for killing weeds.

So, without further ado, let’s get started.

What Are Weeds?

There is no nice way of putting this- weeds are a complete nuisance in your garden. A weed is a term often used for a plant that has no value. By this, we mean that it cannot be used medically, as a material, and it does not have any nutritional purpose.

These “plants” are also renowned for their particularly rapid growth. They germinate extremely easily and compete with crops and other plants for light while also stealing the water and nutrients they need to survive.

The reason weeds are such a nuisance is that aside from stealing water, light, and nutrients from other plants, they can also be poisonous while also producing thorns and burrs. In other words, they can be harmful to both humans and beneficial insects living in your garden.

While weeds are detrimental to crops and plants in the long run, these can normally live together for approximately 2 to 3 weeks. Weeds can later become hosts to pests and other diseases that can, in fact, kill your plants and crops over time.

Whether or not a plant is a weed is in the eye of the beholder. While one person could see a plant as a weed, another could see it as a beautiful piece they believe adds aesthetic value to their garden.

What Is Weed Killer?

As the name suggests, weed killers kill weeds in your crops and garden. Also known as herbicide, these substances control the presence of plants that steal away light, nutrients, and water from your plants and vegetables.

Homemade weed killer being sprayed on a dandelion

There are various types of weed killers, some of which kill weeds while leaving your other plants and vegetables in a healthy environment. Others clear waste ground in order to kill any living plants and crops present in the ground.

While weed killer is most commonly used in an agricultural setting, many households now use these substances in their gardens and vegetable patches. They come in a variety of forms, some of which are completely natural, others which use chemicals to have the desired effect.

The History Of Weed Killers

Weed control technology and weed killers date back to the beginning of agricultural technology. While the act of plowing and hand-weeding dates all the way back to 8000 BCE. This technique was used for the best part of 10,000 years all the way until the 18th Century.

During that stage, an English farmer called Jethro Tull invented the grain drill as well as a variety of cultivation tools, all of which made weeding that little bit easier. These were then improved upon and quickly adopted by countries in Europe and North America.

While the olden days were host to a variety of agricultural tools that helped people, predominantly women and children, to pick weeds more easily without confusing them with crops, the history of weed killers actually started in the 20th century.

Using chemicals intentionally on crops to kill weeds started in the mid 19th century, however, many weed scientists would argue that the real technological evolution behind weed killers started in the 1950s.

The first weed killers included inorganic salts, oils, acids, and a variety of solvents, all of which were used at an astronomical rate and were also extremely high fire hazards. Not only this, they were very toxic to both people and animals.

2,4-D, the first modern herbicide, was developed and released to the agricultural world in 1946, making it the first selective herbicide, which controlled a variety of weeds in crops without killing the crops themselves.

How Do Weed Killers Work?

How weed killers work depends on the type of herbicide you choose to use. That being said, these substances can normally be classified in groups according to the method of application, the activity, the amount of time they take to act, and the chemical family they are classified in.

Weed killer effects before and after

Weed killers work by controlling the proliferation of unwanted weeds in your garden or crops. These substances either destroy them completely or they damage them to the point that they cannot take away light, water, or nutrients from your plants and crops.

Which Plants Do They Target?

The type of plants that weed killers target completely depends on the type of weed killer you choose to use. Commonly, people refer to weed killers as selective or non-selective, this is because they target plants differently.

As the name suggests, selective weed killers are designed to suppress or kill weeds without damaging your plants or crops. They select the weeds to kill based on translocation, the difference in physical and physiological aspects between plants, as well as absorption.

Non-selective weed killers, on the other hand, are designed to kill any plant or crop that is in their way. They are the bulldozer of all weed killers and are most commonly used to clear industrial sites and railway embankments.

Are They Safe For Nearby Plants?

Whether or not your chosen weed killer is safe for your other plants will depend on the type of herbicide you choose. If your weed killer contains the active ingredient glyphosate, you’ll likely kill your weeds and your favorite plants.

This type of weed killer kills everything in its path by overspraying onto your cherished plants. If this weed killer doesn’t kill your plants, it will certainly stunt your plant’s growth, kill the leaves, or even produce leaf spotting.

There are a few ways that you can prevent your plants from suffering because of your weed killer, here are some tips:

Read The Label

As you can see from the above, it is essential that you learn about the chemicals in your weed killer. Another aspect of using weed killer that could affect your plants is the type of spray you use.

Preen Garden Weed Preventer read the label

Fine spray is more likely to drift onto other plants whereas a pressure nozzle targets specific areas of your garden.

Spray When The Air Is Calm

Try and avoid spraying your herbicide during windy days. If the air is calm, the weed killer is less likely to spread to other plants. This is especially true when spraying beds where bulbs have died back as the weed killer can seep into the neck of the bulb, thus stunting its growth.

Aside from being conscious of the wind, you should try and spray on cloudy days as sunny conditions tend to intensify the weed killer thus having a more detrimental effect on your flower beds.

Rinse Sprayers

Aside from dedicating a specific sprayer to weed killer in order to not accidentally dose other plants, you should also rinse it after each use. Try and dump the water you use to rinse your sprayer in non-planted areas to avoid it channeling into your nearby planting areas.

Cover Your Plants With Plastic Sheet

If you don’t have a choice but to use weed killer on windier days then cover your plants with a plastic sheet or cardboard to protect them from spray drift. You should try and only remove the plastic sheet or cardboard when the weed killer is completely dry.

The Difference Between Contact Weed Killers And Systemic Weed Killers

While you already know the difference between selective and non-selective, there are also contact and systemic weed killers available to choose from, both of which have specific uses and need to be applied in different ways.

Contact Weed Killers

As the name suggests, contact weed killers kill the plants with which they come in contact. They can be sprayed on leaves, and as long as the stomata are open, they can stunt its growth and kill the weed.

Because stomata are only open when the plant is growing, contact weed killers need to be applied when the weed is young. They must be applied to living foliage that is green.

Contact weed killers must be applied at the beginning of the day in order to give them time to work their way into the stomata to kill the weed.

Systemic Weed Killers

While contact weed killers enter through the leaf of the plant, systemic weed killers have the ability to enter through virtually any part of the plant, allowing themselves to move their way through the plant’s transport system to kill every inch of it from its root to its leaves. 

These types of weed killers are more effective as they can be applied at any time of the day and do not require you to identify weeds early on. That being said, you’re better off applying them when it is not raining as they can be washed off the soil thus making them less effective.

Are Weed Killers Safe?

While there are now a mountain of laws that ban certain weed killers because of their toxic properties, there is still a lot of discussion surrounding the topic, especially when it comes to children, food, and pets.

Child with weed killer spray

Here is some additional information:

Child And Pet Safety

While many homeowners use chemical-based weed killers such as 2,4-D and glyphosate in areas where their children and pets play, there have been reports that some of these more toxic substances have been identified as carcinogens and endocrine disruptors.

With this in mind, we suggest that you opt for natural weed killers where possible, or better yet, pull as many out by hand as you possibly can. You should also only use weed killer when your children and pets are not in the vicinity.

By leaving the area where weed killer has been applied to dry while there are no humans or animals around, you’ll be less likely to spread toxic chemicals around your household. We suggest you avoid toxic chemicals on your fruit and vegetable patches.


Today, there is a lot of controversy regarding weed killers and food safety. Once again glyphosate and other acid-based weed killers have been proven to be making their way into foods across the world.

While the debate still remains as to what harmful effects these have on the body, scientists are starting to come out, saying that there could be links between these chemicals and genotoxicity (the mutation of human cells), carcinogenicity, as well as reproductive damage.

With all the above in mind, avoiding chemical-based herbicides on your food could be your best bet if you want to maintain a healthy household. This is also a key reason why the demand for organic food has risen in the United States.

Selective Weed Killers Vs. Non-Selective Weed Killers

While many assume that non-selective weed killers are more harmful than selective ones, there is no proof that this is the case. In fact, you could argue that because non-selective weed killers kill everything they touches, they are less likely to leave traces on crops, and therefore, food.

That being said, when it comes to using non-selective weed killer on lawns or in your garden, you could be leaving very harmful traces of chemicals in areas of your home where your family, kids, and pets spend their time.

Simply put, non-selective herbicides are more destructive and very often found in public spaces such as industrial sites and railways whereas selective weed killers are often found in your home and are more likely to subtly make their way to your family and even your food.

The Difference Between Weed Preventers And Weed Killers

Many confuse weed killers with weed preventers. Weed preventers are also referred to as pre-emergent herbicides while weed killers can be referred to as post-emergent herbicides. The key difference is that weed preventers stop weeds from growing the first place.

Preen Weed Killer Review

Weed preventers are applied to soil in order to stop weed seeds from germinating. They come as both chemical substances and non-toxic or organic ones.

On the other hand, weed killers destroy weeds once they have started to grow. They also come in various synthetic and organic forms. While both are very effective tools, post-emergent herbicides mean that you will have to remove the weeds by hand once they have died.

How Effective Are Organic Weed Killers?

With the public’s growing demand for healthier alternatives to weed treatment, more and more companies are offering organic weed killers that do not use any toxic chemicals to destroy weeds.

Despite the fact that there is limited information on the efficacy of these organic products, many are opting for organic weed killers that use essential oils and other natural plant extracts to target weed growth.

While weed killers made of essential oils, soaps, or acetic acid, destroy the leaf cuticles and cause cell leakage they do not provide long-term control of weeds with extensive underground storage structures.

This means that weeds such as tubers, rhizomes, and bulbs can continue to grow. One of the best ways to increase your odds of killing weeds with organic weed killers is by creating good spray coverage, applying them in warm conditions, and treating weeds when they are small.

The Best Way To Apply Weed Killers

Try Pre-Emergent Weed Killer

Your best bet for killing weeds is to catch them before they even set seed by using pre-emergent weed killer. These types of weed killers stop weed seeds from germinating in the first place. They’re especially useful for preventing annual summer weeds.

Destroy Them When They Are Young

That being said, if the weeds are already there, catch them before they grow. You can either do so by pulling them out from their root, or using a weed killer that kills the weed upon contact with the plant’s tissue.

Cut Down Tougher Weeds

If you’re suffering from an overgrown and strong population of weeds, we recommend you cut them down and wait for new leaves to appear. This will make it easier for the weed killer to infiltrate the plant, thus killing it more quickly and effectively.

Time Your Weeding According To The Weather

The best way to effectively kill weeds is to do it during several days of dry weather. If you apply weed killer before it rains it may wash off your weeds or get diluted by the rainwater.

Rain drops on weeds.

You should also try and apply weed killer when it is not windy as you may find that your weed killer spreads to other, more desirable plants, thus killing them in its wake.

Last but not least, if you’re an avid gardener that times your planting, take the needs of your other plants into consideration. For example, if replanting, use weed killer early on to avoid the onset of weeds in the first place.

Weed Killing Tips

Now that you know the best way to apply your weed killer, here are some other tips that can make your weeding experience that little less tiresome. Here they are:

Let Hidden Weeds Sleep

The fact of the matter is, your garden is filled with weed seeds. Luckily, it is only the ones that are an inch or two from the top of your soil that actually germinate. With this in mind, you should only dig in your garden when you really need to.

By minimizing soil disruption you’ll be less likely to suffer from an eruption of weeds in your garden. If you want to plant something, dig smaller and deeper holes in your garden without disrupting the soil around that space.


Mulch will stop your weeds from getting too much light. Make sure that you replenish the mulch regularly to keep it to a minimum of two inches deep. You can also cover the soil surface with biodegradable materials such as cardboard or newspaper.

Weed After A Drenching Rain

If there has been a big downpour of rain in your area, schedule your weeding once the rain has stopped and your soil is still wet. By doing your weeding when your soil is wet, you’ll be more likely to pull the weeds out from the root, stopping them from growing back.

Water Your Plants, Not Your Weeds

If you really want to stop weeds from growing, don’t water them! By placing a soaker hose underneath your mulch and watering only your plants, you’ll stop water from seeping into the weeds, thus stunting their growth in the first place.

Watering plants.


Weed killers are powerful substances that will leave your garden looking luscious while also saving you a lot of time pulling out unwanted visitors.

We’ll also be sharing some information on top features to pay attention to when choosing the best weed killer for your outdoor space.