Herbicides are the most common solution applied for weed management. For example, around 19% of the world’s glyphosate-based weed killers have been used in the United States alone since 1974. But the popularity of chemical weed killers means that their active ingredients linger long after they’ve done their work.
The risk of soil contamination and effects on fauna by using synthetic herbicides has led to the rise of organic weed killer alternatives. These products can provide the same herbicidal action without harming the environment.
In this guide, we’ve collected the best organic weed killer products that any gardening enthusiast or farmer can use for weed control. It contains a detailed description and review of the active ingredients of organic weed killers, and a section on how they work and the best scenarios in which to use them.
If you’re looking for a more eco-friendly solution to getting rid of weeds and other unwanted growth in your garden and lawn, then this is the guide for you.
Green Gobbler Vinegar
- The 10 Best Organic Weed Killers Review
- Green Gobbler Vinegar Weed & Grass Killer
- Espoma Organic Weed Preventer
- Natural Armor Weed and Grass Killer All-Natural Concentrated Formula
- Doctor Kirchner Natural Weed & Grass Killer Pet and Kid Safe
- ECO Garden PRO Organic Vinegar Weed Killer
- BioSafe Systems 7601-1 BioSafe Weed Control Concentrate
- Weed Slayer Organic Herbicide Natural Grass and Weed Control
- Bonide (BND7465) – Burnout Concentrate, Fast Acting Weed and Grass Killer
- Avenger Organics Weed Killer Concentrate
- EcoSMART Weed and Grass Killer
- What To Consider When Looking For The Best Organic Weed Killer
- Why Use Organic Weed Killers
Organic Weed Killer Comparison Table
|Name & Brand||Visible result||Glyphosate free?||Size||Price|
|Green Gobbler Vinegar||6 hours||Yes||1 Gallon|
|Espoma Organic Weed||6 hours||Yes||25 lb|
|Natural Armor Weed||2-3 hours||Yes||128-Ounce|
|Doctor Kirchner Natural||1-3 hours||Yes||2.5 Gallon|
|ECO Garden PRO||24 hours||Yes||1 Gallon|
|BioSafe Systems 7601-1||24 hours||Yes||1 Gallon|
|Weed Slayer Organic||24 hours||Yes||Two 32 fl./oz|
|Bonide (BND7465)||Just hours||No||128 Oz|
|Avenger Organics||2 hours||Yes||32 oz|
|EcoSMART Weed||Just hours||No||24 oz|
The 10 Best Organic Weed Killers Review
Each of these products can deal with many varieties of weed, but they have their special mechanisms of action that allow them to be as versatile and targeted as you like.
Green Gobbler is a contact weed killer that targets broadleaf weeds like dandelions, white clovers, and chickweeds. As a post-emergent herbicide, it is especially effective on weeds that have already started growing. For areas with large growths, it’s an effective blanket option that can target surface weeds without affecting plants, microorganisms, or soil quality.
This weed killer can be used via spot spraying on weeds. Blanket application should be kept to a minimum, as the formula doesn’t discriminate between plants. If the area contains delicate plants such as flowers, you can dilute Green Gobbler to 10% concentration to avoid oversaturation. Avoid use during wet conditions, since the formula needs time to settle in the broadleaf to work.
The best cases to use Green Gobbler would be around areas that see high amounts of foot traffic. While the acetic solution in the formula is four times stronger than table vinegar, the organic base of the product makes it dissolve faster, eliminating the risk of accidental ingestion or contact by either humans or animals.
The active ingredients of Green Gobbler are derived from a concentrated form of vinegar and corn. It’s approved by the Organic Materials Review Institute (OMRI) for both agricultural and home use, though the manufacturer recommends application to small-to-medium sized plots of land for the best results.
Green Gobbler works by settling in via the surface of broadleaf weeds, which absorb them during hot or sunny conditions. Once the formula has penetrated the main body of the weed, the acetic acid dissolves the plant from within, causing it to wither and fade within one to two days. Depending on the garden, the weed can either be pulled manually from the ground or left to contribute to the mulch of the soil. Expect broadleaf weeds to desiccate within 24 to 48 hours.
As a post-emergent herbicide, this product needs to be consistently reapplied to ensure that the area remains-weed free. Germinating weeds like dandelions should be allowed to grow slightly before applying Green Gobbler, as an early application can minimize the effects of the herbicide.
You can also use Green Gobbler on areas that need scouring of all plant life such as fences, pavements, and other garden fixtures. Blanket spraying will get in the middle of cracks and ensure that any growing leaves wilt away.
Overall, Green Gobbler is one of the best & safest weed killer products that any homeowner can use. The contact formula weakens weeds from within, allowing you to identify, stop, and pull out weeds before they become unmanageable.
Granulated for easy application and storage, Espoma Organic Weed Preventer is an all-natural pre-emergent herbicide that can get rid of germinating weeds before they can fully grow. It also increases the nitrogen content of the soil, making it an excellent addition to small patches of vegetables like sweet corn.
Pre-emergent formulas work by preventing the growth of weeds instead of wilting them once they’ve already grown. This makes products like Espoma work great with large tracts of land such as lawns and vegetable gardens. In addition, the granulated mix means that it stays in the ground longer than liquid concentrate, so you only need to reapply it twice a year.
Espoma works best during the pre-germination season in the early spring and fall. Apply a heavy layer on your lawn or a light layer on a vegetable patch. Only apply on dry soil with a drop or broadcast spreader, overlapping slightly to prevent striping. If no rain is to be expected within 24 hours, lightly water the top layer to ensure it sinks into the soil.
Only use Espoma on established lawns. Application on pre-seeded or pre-planted soil will kill germinating weeds, but may also inhibit the normal growth of future plants. This product does not work as a post-emergent herbicide and will do nothing against already growing weeds like dandelions and thistles.
The active ingredient of Espoma is corn gluten meal, a popular agricultural pre-emergent herbicide. As a byproduct of corn milling, it’s a common substance that many farmers use on their lands. It’s about 10 percent nitrogen, which benefits both the soil and the other plants that are growing in it.
Corn gluten meal changes the process in how weeds grow: it doesn’t stop them from sprouting, but it prevents them from establishing a root network. Without a root network to extract nutrients from, weeds won’t survive for long. This is also why it’s important to apply Espoma on dry soil, in dry conditions – it’ll prevent any weeds from recovering after their root systems have been cut.
Timing is essential when using pre-emergents like Espoma. While you can water the layer slightly for it to sink into your lawn, you need a dry period for the germination process to come to a halt. It can be difficult to get this timing right for the first couple of times. But once you master both application and timing, your lawn will look healthier and weed-free for most of the year.
Natural Armor is one of the most versatile weed killers out there, with a quick spray and wait formula that gives you visible results within hours. Targeted to remove almost 250+ varieties of weeds, it’s an excellent general-use herbicide that can be spot sprayed over stubborn patches of weed.
The ready-to-use formula makes applying Natural Armor quite easy. Load the sprayer with the formula, target vegetation you want to remove, and spray until the plant is thoroughly wet. Use during dry, sunny, or warm days for the weed’s natural absorption to take place. The product is already measured for spot spraying, so there is no need to dilute the concentration.
Using organic herbicides reduces the risk of soil contamination, allowing for more delicate growths like flowers and herb gardens to remain intact and weed-free. It’s an even better option if there is wildlife in the area that could be affected by using herbicide since an all-natural formula can significantly reduce any effects outside of the herbicide’s intended use.
Natural Armor’s primary components are vinegar and lemon extract, which account for over 90% of the solution. The natural acidic properties of these compounds choke off nutrient retention and gathering, attacking the weed from the inside once it’s been absorbed into the plant. With repeated, consistent use, this product can remove most weeds within a week or less, depending on the right conditions.
Once Natural Armor has been absorbed by the weed, it’ll take a few hours or less for the acidic properties of the primary components to wither the plant. Copious amounts of glycerin (a moisture-trapping additive) ensures that the formula stays within the weed until it’s fully permeated throughout the plant. This makes Natural Armor effective at getting rid of sprayed plants without touching any other growth in the vicinity.
Natural Armor is best used for small-to-medium plots of land, as the formula cannot be distilled to stretch out its efficacy. It can also work for small-scale agricultural vegetation like vegetable gardens, but it should be applied carefully as a non-discriminatory herbicide. The spray nozzle makes the application ideal for spot spraying, especially for tall weeds such as dandelions.
For an easy-to-use solution that can target most varieties of weed growth, Natural Armor Weed And Grass Killer can help reduce the amount of unwanted vegetation in the area. It’s also safe for use around pets and humans, so minimal precautions are needed after you have applied the product.
Doctor Kirchner’s formula is a bit different from other products on this list, as its active ingredients are a mixture of ocean saltwater, food-grade vinegar, and soap. It’s a spot-spray formula that’s designed to get rid of grassy weeds like crabgrass, though it performs suitably with spot-spraying large patches of broadleaves.
Spray the Doctor Kirchner Natural Weed & Grass Killer on the area with the most growth until weeds are thoroughly soaked. You should see some wilting within the next 12 to 24 hours, after which weeds can be removed and other plants can be introduced to the area. Repeat applications may be required if the area experiences rain or other wet conditions, or if irrigation is present.
Doctor Kirchner made this product for safe, effective, and consistent use in areas where pets, children, and other people frequently spend their time. Aside from initial precautions when using the spray (such as gloves and protective eyewear), the product degrades quickly after application, with no contamination or other unwanted effects on the soil. This also makes it ideal for use on lawn installations like fencing.
The active ingredients in this herbicide are ocean water and vinegar, which work by disrupting the natural growth cycle of plants. The combination of these two ingredients makes a powerful growth-inhibiting cocktail of chemicals that can dissolve grassy weeds and weaken broadleaves enough for them to die off. For more resilient weeds, another application will be enough for the active ingredients to break through the plant membrane.
Blanket spraying this product in an affected area will affect all vegetation, so it’s also ideal for rocked landscapes or other lawn installations that are experiencing unwanted growth. Saturating places like gravel patios, brick walkways, or fence posts can kill any greenery growing on them, with repeat applications getting rid of all but the most stubborn of weeds.
Doctor Kirchner Natural Weed & Grass Killer is the best organic weed killer for lawns that have grassy weeds in them, as the formula is ideal for blanket spraying large areas. It has a long shelf life, so each purchase of this product can last you for several seasons.
Specially formulated for the ease of use around livestock, animals, and insects, ECO Garden PRO kills weeds like clovers, thistles, and moss within 24 hours. The ingredients are all-organic and degrade upon contact with the soil, making this product safe to use around groundwater areas without the risk of contamination.
The ready to use formula can be applied via blanket or spot spraying weeds and can get rid of vegetation that is growing on walls, fences, pavements, mulch beds, and farmland. It can be used in either commercial, residential, or industrial plots of land. Apply it in the middle of the day during warm weather for best results and faster action.
ECO Garden PRO is best used for areas where there is plenty of wildlife and other microorganisms that are at risk of being affected by regular herbicides. The natural ingredients in this product don’t contaminate soil, water, or other areas when applied. This reduces the risk of disrupting the natural ecosystem of the area, which is crucial if there are livestock, fish, or bees present.
The main ingredients of ECO Garden PRO are natural rock salts, safe plant activators, and traces of acetic acid. These are natural ingredients that have no adverse harm on humans, animals, and insects, making this product one of the safest to use in heavily populated areas. It’s especially effective in areas with plenty of natural wildlife like fish since the ingredients disperse in water.
ECO Garden PRO works by disrupting the nutrient and growth systems of weeds, disabling their capability to leech water and nutrients properly from the surrounding soil. Within hours, the acidic properties of the formula wither the plant from the inside, allowing easy identification and removal within two days. For humid or wet areas, reapply regularly to ensure that all weeds get affected by the product.
Overall, this product is a great choice for weed removal in places close to wildlife or are in areas that have pre-existing fauna such as insects and other microorganisms that need to be left untouched. If you need an eco-friendly herbicide that only kills vegetation and affects nothing else, ECO Garden PRO is the right choice.
BioSafe Systems 7601-1 is a non-migratory herbicide that can burn down and decay annual and perennial weeds within two hours. Suitable for both broadleaf and grassy weeds, this formula works its best on plots of land that are targeted for reseeding. Alternatively, spot spraying on large patches of weed works just as well.
To use this product, apply directly to the weed itself and soak thoroughly. While the absorption action is more reliable on a hot day, BioSafe Systems 7601-1 also works during wet conditions. After application, the weeds should shrivel up and wilt in two to three hours. It can be used in a variety of areas from patios, walkways, and vegetable gardens.
The biggest benefit to using this product is that it has virtually zero risks of soil contamination. The active ingredients are non-volatile and water-soluble, which make it a great weed management tool for agricultural plots and home gardens. For this reason, it’s also rated safe for use by OMRI. BioSafe Systems 7601-1 is safe to use around pets and other animals, but the active ingredients may be a bit too strong for smaller organisms such as bees.
BioSafe Systems 7601-1 is primarily made up of ammonium nonanoate, a plant-derived broad-spectrum herbicide. It’s known for its remarkable degradability once it reaches the soil, due to being digestible by microbes. On average, the half-life of ammonium nonanoate is less than 24 hours in most soil, regardless of the environment or other conditions.
The carbocyclic nature of this product functions like other organic ingredients such as acetic acid and salt, disrupting any vegetation’s cell structure from the inside. It leaves no residue once the weed has fully digested the active ingredients, and will not leak out to the surrounding soil after permeating the plant.
The concentrate can be distilled further to stretch the contents of the bottle: for example, 16oz of the formula for every 1 gallon of water. Precaution is needed when using this herbicide (avoiding contact with the skin, eyes, and nose,) but the area is safe for human activity within two days of use. Reseeding and replanting can occur as soon as 4 days after the last application.
Glyphosate is a key yet harmful ingredient in many synthetic herbicides. Weed Slayer Organic Herbicide uses eugenol, a natural essential oil that functions as an organic alternative to glyphosate. Primarily used as a post-emergent herbicide, repeat applications to stubborn grassy weeds can kill growth right down to the root. It’s also registered safe for use by the Washington State Department Of Agriculture.
Weed Slayer comes in two bottles that need to be mixed. The first is the actual eugenol concentrate that can kill the weeds, while the second is AgroGold, a mixture which contains soil-enhancing bacteria. Mix both parts just as the instructions specify, and blanket spray on the desired area. One of the suggested mixes is 3oz of solution per 1 gallon of water. Use during hot weather for maximum absorption.
If your weed problem isn’t that serious or you have a defined area in which to apply the product, Weed Slayer is a good choice for weed control. The product works best on grassy weeds that have invaded a specific patch of soil since the residue of the product can stay for up to 8 to 10 days after application. After that time, it’s safe to replant or reseed the area again.
The eugenol concentrate is the active ingredient in Weed Slayer, while the addition of molasses extract boosts the soil’s natural production of microorganisms. This means that the product leaves residual traces of itself on the soil, but the active effects wear off after a week. Mixing AgroGold in the solutions also helps restore the soil to its microbe-infused state, prepping it for new planting.
Weed Slayer works in two ways: first, the eugenol enters the weed’s systems, translocating to the root systems and killing the plant from the inside. At the same time, the molasses extract increases the levels of phosphorus in the soil, discouraging further weed germination. Second, the AgroGold solution helps restore any microbial imbalance that may have occurred in the soil because of the herbicide’s effect.
Overall, Weed Slayer works well for small-to-medium grassy weeds that take time to kill. One application can give you visible results in hours, while repeat applications can get rid of most growths completely within two weeks.
Bonide Burnout Weed Killer is a herbicide made especially for colder and wetter environments, in addition to being human and pet-friendly soon after application. As a non-selective blanket spray, it can get rid of most vegetation on hard stone installations like patios, gazebos, fences, and sidewalks. It also doesn’t translocate into the soil, which lowers the risk of contamination.
The concentrated formula needs to be diluted in water in a 1 to 3 ratio (8oz in 24 fluid ounces of water) before using. A measuring cup is provided with your purchase to ensure consistent ratios between multiple uses. Once mixed, apply to weeds and other unwanted growths. Blanket spray the formula for lawn installations, and spot spray for broadleaf growths like dandelions.
Spraying this product on post-emergent weeds is a great way to keep their growth under control, as the formula works down the plant roots. One thorough application is enough to keep grassy weeds away for an entire season, though effectiveness will vary between environments and the weed that you’re using it on.
The active ingredients in Bonide are citric acid and clove oil, which work well on grassy weeds that compete with your planted turf like crabgrass. The high concentration (almost 30%) of active ingredients is a powerful mix that can work on weeds even without the use of a surfactant. As an acid solution, Bonide has high permeability and needs little external help to reach the core of the plant.
The acidic properties of the formula choke their structural integrity, weakening them from the inside and cutting off their ability to gain nutrients from the soil. Eventually, the weeds wither away and can be either pulled by hand or composted by the microorganisms in your soil.
Bonide is also waterproof 40 minutes after application, making it a perfect fit for areas that experience frequent rain or light showers. For the best results, reapply the product as the seasons turn, or as necessary with more stubborn weeds. Keep pets away for an hour after applying this product, as the high concentration can have negative effects once it comes into skin contact.
Ideal for immature weeds that haven’t fully grown, Avenger Organics Weed Killer is suitable for weeds like common chickweed, sowthistle, bermudagrass, and dandelions. EPA registered and OMRI approved, it also has the backing of the Washington Organic Food Program (WSDA) for agricultural and home gardening use.
Mix the product with water in a 1:6 ratio for small, annual weeds and 1:4½ for weeds that grow taller than 6 inches. Shake the product well before spraying, then apply to weeds thoroughly. Wait for weeds to display a white emulsion before moving on – the lack of this sign means that the ready-to-use mix and post-mix concentrate hasn’t blended well.
For best results, use Avenger Organics in sunny conditions to accompany the natural water absorption cycle of plants during hotter weather. For cooler climates, only apply in temperatures above 40 degrees Fahrenheit. Do not use an irrigation system, as the formula may clog the tubes.
Avenger’s primary use is for plots that have delicate growths, such as herb gardens and ornamentals. The formula is gentle enough to get rid of stubborn weeds via spot spraying, but not destructive enough to affect other plants during blanket application. The natural ingredients also make it pet friendly, though the acidic composition needs time to dry before animals can go through the applied areas.
Most Avenger’s ingredients are all citrus-based, derived from products like oranges and lemons. These ingredients are a powerful acidic solution that neutralizes weeds from within besides having a pleasant scent, unlike most herbicides. With 70% of Avenger made from these active ingredients, it’s a mix that can deal with most grassy and broadleaf weeds with a single application.
Because of the ingredients, the effects of Avenger can differ across different weeds. While you can reasonably expect to see results within half a day, the performance of the product relies on how ideal the concentrate mix is. You may have to make several attempts to get the ideal mixture for dealing with the specific vegetation that you are looking to remove. It’s also not advised for use during wet conditions, as the citric acids wash off easily.
EcoSMART Weed and Grass Killer is a ready-to-use spray herbicide derived mostly from plant-based oils. Ideally used on lawn fixtures and small, raised garden beds, it’s also pet-friendly and can give you visible results in less than a day. It targets most varieties of weed but has proven most effective when spot-sprayed on individual broadleaf varieties.
To use EcoSMART, shake the bottle well and spray the area thoroughly. The solution needs no dilution, as the product is already measured per bottle for ease of use. Test certain areas like bricks and walkways to see if some staining would occur before use. As a non-discriminatory spray, keep desired plants to keep far away from the area of application or shield them with cardboard or plastic.
Ready to use sprays can be used on almost all weeds with little to no prep, making products like EcoSMART particularly useful in urban gardens. The spray bottle makes it more conducive to spot-spraying smaller growths, and the concentrated formula isn’t harsh on the surrounding environment.
EcoSMART’s active ingredients are mostly extracted from plant oils like clove. This makes it safe to use in areas with children and small pets, though the smell of the product may linger for a while. As an organic herbicide, you also don’t have to worry about the soil quality lowering drastically if you use it on a planted plot.
The active ingredients work much like other vinegar concentrates out there, working its way into the core of the plant once applied. The effects are more potent on growths that have a lot of surface areas like vines and moss since the solution can get into the plant system from multiple entry points. This also means that this herbicide works well in hot or humid conditions, due to the high concentrate ratio.
However, the product’s effectiveness diminishes with more stubborn weeds like dandelions and thistles. The small bottle also means you get a smaller return on investment if you purchase it for a lawn. EcoSMART is best used for small-scale, spot spray applications of smaller weeds that don’t take a lot of solution to remove.
What To Consider When Looking For The Best Organic Weed Killer
To get the most out of your weed killer, it’s best to play to the distinct strengths of each product. Working with their mechanisms of action and targeted effects is a more effective way to use these products.
Pre-Emergent vs Post Emergent Brands
The state of weeds in your garden will determine how you’ll treat them. If you’re looking to stop weeds from growing, a pre-emergent formula works best. For dealing with already existing patches of weed, a post-emergent herbicide will do the trick. Confusing the two will diminish the effectiveness of your herbicide, and may end up negatively impacting the plants already growing there.
The Presence Of Wildlife, Pets, Or Other People In The Area
Organic weed killers may impact their surroundings less, but it’s still not an effect that should be ignored. Different brands have different soil-half lives and may require some time to either settle or dry before others walk or visit the area. For children and small pets, some herbicide ingredients can be mildly irritating and cause several skin disorders if they wander in too soon.
Spot Spraying vs Blanket Spraying
Since most organic herbicides are non-discriminatory, you’ll have to be careful about the application process to prevent unwanted effects on plants you want to keep. Some products are gentle enough to allow blanket spraying over delicate plants, while others need a precise spot spray application to prevent harming other growths. Checking whether your product uses one or the other can help you avoid damaging your other plants.
Weather Conditions During Application
Ideally, organic herbicides should be applied on hot days where the weeds can absorb them faster. But for areas that experience plenty of rain and other cool weather, that may not be an option. Weather also affects how well a herbicide works, so keep this in mind before applying the product.
Choosing the wrong weather can result in the product being washed off or rendered inert before it’s had a chance to work, wasting time and giving weeds more time to grow.
Proximity To Water Or Different Soil
There are some brands of organic weed killer that translocate when applied, moving from the leaves to the roots. This can be an issue if you’re concerned about ground or water contamination since some ingredients can leech into their surroundings. As organic herbicides, the effects aren’t as negative as synthetic brands. However, you may decide to monitor this particular factor for aesthetic or environmental reasons.
Why Use Organic Weed Killers
Aside from being eco-friendly alternatives to harsher chemicals normally found in synthetic herbicides, there are other advantages to using organic herbicides that go beyond being simple alternatives to store-bought brands. Here are some reasons your next herbicide should be organic.
It’s Safer For Everyone
Organic herbicides have less debilitating effects on humans and animals during and after application. Unlike synthetic products, accidentally coming into contact with organic weed killers is never fatal, and only mildly irritating at worst. You should still take proper precautions when using them, but you can rest easy that they aren’t extremely dangerous to use.
It Guarantees Safe Consumption Of Homegrown Plants
Using laboratory chemicals on plots like herb or vegetable gardens always carries the risk of contamination. However, organic herbicide degrades quickly into the soil and has a relatively short soil half-life, ensuring that anything you grow, you can eat without worrying about chemical poisoning. This benefits growing both human and animal food.
It Helps You Keep A Closer Eye On Your Garden
Organic herbicides force you to pay attention to your garden every time you use them, allowing you to spot early issues and other potential problems that you might have missed. This promotes a feedback loop of you taking more care of your plots, which helps them grow better. Once you’ve established a routine using organic weed killers, the chances of your garden improving will rise steadily.
It Allows Your Garden To Cope Better With The Weeding Process
Weeding isn’t a singular act: the very act of weeding can disrupt soil, ruin root networks, and cause a nutritional imbalance in large tracts of soil. Adding the extreme chemical effects most synthetic herbicides have on top of that mix can degrade soil health and affect plant growth. Organic weed killers are more gentle, allowing your lawn and garden time to recover from weed management.
It Can Help You Stick To Environmental Regulations
The harmful effects of synthetic herbicides have been well-studied and recorded, and in response, states and local zoning groups have issued regulations to minimize these effects. For example, the National List of Allowed and Prohibited Substances lists organic substances safe for farming and prohibits several synthetic substances. This list is constantly being updated – so to avoid potential violations, using an organic weed killer is a prudent step many gardeners should take.
These products can work as general-purpose herbicides, but one of the better ways to get more use out of them is carefully evaluate what your garden needs in terms of weed control.
Organic weed killers need to fulfill two important criteria: they should be a reliable tool for weed management, and they should not harm the flora and fauna around them. Choosing the right brand goes a long way towards not only keeping your gardens and lawns weed-free, but it also saves you a tremendous amount of time and money.
While all these products are outstanding organic herbicides in their own right, proper application and maintenance are still some of the best tools in your arsenal for weed control. Wearing protective equipment, following the instructions, and applying the product consistently are essential towards building an eco-friendly garden with these organic weed killers.