There are times when the only way to get rid of a stubborn weed is to treat it with an herbicide. Don’t be afraid to use herbicides if you need them, but try other control methods first. Pulling, hoeing, tilling, and digging will often take care of weed problems without the need for chemical sprays. Let’s learn more about using herbicide in gardens.
What are Herbicides?
Herbicides are chemicals that kill plants or prevent them from growing. Their method of killing plants is as varied as the plants they kill. The first step in understanding herbicides is to read the label. Labels tell you how to use herbicides safely and effectively. It is illegal to use herbicides for any purpose or by any method other than as indicated on the label.
Here are some tips to help you use herbicides safely and effectively:
- Avoid using herbicides on windy days and near bodies of water.
- Always wear a protective mask, gloves, and long sleeves.
- Make sure children and pets are indoors when you spray herbicides.
- Buy only as much herbicide as you need and store it in a safe place, out of the reach of children.
Types of Herbicides
Herbicides can be divided into two main categories: selective and non-selective.
- Selective herbicides kill certain types of weeds while leaving other plants unharmed. The herbicide label lists the target weeds as well as garden plants that are unaffected.
- Non-selective herbicides, as the name implies, can kill almost any plant. Selective herbicides are useful when treating weeds in lawns and gardens. Non-selective herbicides make it easy to clear an area when starting a new garden.
Selective herbicides can be further divided into pre-emergent and post-emergent herbicides.
- Pre-emergent herbicides are applied to the soil and kill young seedlings soon after they emerge.
- Post-emergent herbicides are usually applied to the foliage where they are absorbed into the plant tissue.
The type determines when to apply an herbicide. Pre-emergents are usually applied in late winter or early spring, while post-emergents are applied in spring after the weeds begin to grow.
When using herbicide in gardens, take care to protect the plants you don’t want to kill. If you have identified your weed, you may be able to find a selective herbicide that will kill the weed without harming garden plants. Those containing glyphosate are good herbicides for hard to control plants and unidentified weeds because they kill most plants. Protect the other plants in the garden by making a cardboard collar to fit around the weed before applying the herbicide.
Note: Chemical control should only be used as a last resort, as organic approaches are more environmentally friendly.
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Taking care of post-emergent weeds can be tricky. You want to kill the weeds, but not your grass. You don’t want to just cut your lawn, but be on the cutting edge.
But no matter what you do to prevent weeds from growing, those pesky lawn-wreckers pop their ugly little heads up out of the soil anyway. There are too many for pulling, so what now?
Here are a few tips for fighting back against weeds using post-emergent herbicides.
What Are Post Emergent Herbicides?
Simply put, post-emergent weed control is a strategy to take on weeds that have already popped up. There are things you can do to try and prevent weeds from ever showing up, but once they do, post-emergent herbicides are your new best friend.
Post-emergent herbicides use combinations of chemicals to kill the weeds and (hopefully) prevent them from coming back. They do this by attacking the roots of the weed or even the leaves. Some weeds are tougher to kill than others.
You will want to choose your herbicide carefully and consider a few basic questions.
What kind of weeds are you targeting?
Is it a stand-alone weed patch?
Will contact with other plants (such as your grass) be unavoidable?
How safe is it to use around your family and pets?
What extra safety precautions will you need to take?
Different Types of Post-Emergent Herbicides
Believe it or not, there are different types of post-emergent herbicides out there on the market. That’s actually a good thing! The different types allow you to pick one that will be most effective for the exact situation you’re facing.
Systematic vs Contact
The first two types of post-emergent herbicides to understand are “systematic” and “contact” herbicides. They each work differently and have different uses.
Systematic herbicides are absorbed by the weeds. The product flows through the plant, killing it from the inside out, roots and all. They’re a great choice for when you’re dealing with perennial weeds that you don’t want to see now…or next year.
Just like it sounds, this type of herbicide kills weeds on contact. They work by destroying the leaves and stem of the plant. With the exposed portions destroyed, the weed cannot continue its life cycle and dies. Contact herbicides are the right choice for annual weeds and small weeds.
Selective vs Non-selective
The next choice you need to make is selective vs non-selective herbicides. This is a crucial choice. If you choose the wrong one, you can risk damaging some of your lawn or landscaping.
As the name suggests, selective herbicides are choosy. They target certain weeds and will only harm those specific plants. If you’re having weed problems in your lawn that’s close to some landscaping plants you’d rather not harm, a selective herbicide will allow you to kill the weeds without harming the plants you like.
You guessed it. Non-selective herbicides don’t ask questions, they just kill everything in sight. If you’re looking to clear out a patch that has been overtaken by weeds, this is your weapon. Be careful if you’re close to any other plants that you’d like to keep because these herbicides will take out the good with the bad.
Using Post-Emergent Herbicides Effectively and Safely
Now that you’ve chosen the proper herbicide for your situation, it is important that you get the job done properly. The good news is that the most effective way to apply your herbicides is also going to be the safest. Here are a few pro tips to keep in mind.
Study that label
Seriously. You may think you know what you should do, but read that label. It should tell you the proper technique for using your chosen herbicide for maximum effectiveness and also give you tips on how to avoid endangering any other plants or even your family or pets. You may have to peel back the label to get at the full information, but it’s worth the effort. Read it. Read it all.
Wear gloves, long sleeves and pants, and even goggles if the label recommends it. Yeah, it may be warm or you may look goofy to the neighbors. It’s worth it to do the job right.
Know the weather
Is the rest of the day going to be hot and sunny? Rainy? Weather conditions can alter the effectiveness of your herbicides. Don’t forget to pay special attention to the wind. If the wind is blowing, leave your weed project for another day. The wind can spread your herbicide to places you don’t want it, like your rose bushes or neighbor’s yard.
Measure, measure, measure
Ever heard of the old saying, “Measure twice, cut once!” the same applies here. Know the area of ground you need to cover and just how much herbicide you need. You don’t want to over or underutilize your weed weapon.
Keep the area blocked off
If possible, block off the affected area with rope, tape, or some kind of marker. Since you read the label closely, you know how long you need to keep people and pets away. Let your family know what you’re doing and where, so they don’t have to guess. If it’s a large project, you may want to give your neighbors a heads-up as well. It’s the polite thing to do.
Pro Tips to Up Your Weed-Killing Game
Dealing with weeds in your lawn or garden isn’t fun. At best, it’s a nuisance. At its worst it can feel like an endless game of Whack-a-mole as the weeds pop up, you knock them down, and more pop up a few feet away.
Believe it or not, lawn care has come a long way in recent years. New techniques and new products can help bring your lawn up to date. Here are a few tips to help you get the job done as efficiently as possible.
Know your coverage area
Have you ever been applying herbicide and felt like, “Hey, I think I already did this part of the lawn.” It’s okay. We’ve all been there. The problem is that when you double cover you’re wasting your time, herbicide, and money. Luckily, you have better options.
Try using LawnStar Blue Spray Pattern Indicator or any other spray indicator when applying herbicides. These products mix with any herbicide to clearly mark where you’ve sprayed by coloring the turf blue. Don’t worry, the effects fade away in 24-48 hours. No more worrying about missing spots or wasting herbicide by over-applying.
Give your products a boost
What if you could make your post-emergent herbicide cover more ground, be more effective, and even have longer-lasting effects? This is where using a surfactant comes in.
You may not realize it, but a lot of the herbicide you are spraying is simply hitting its target, beading up and rolling off. It falls to the turf, useless. It’s not a flaw, it’s just nature.
Surfactants help any herbicide break through that barrier and adhere to the weed. The result is that you can use less herbicide, cover more ground, and see better results. Every time.
Surfactants like our LawnStar Non-Ionic Surfactant, are products that pay for themselves by maximizing the effectiveness of your herbicides.
Win the War on Weeds
Let’s face it, weed control is a constant battle. However, it’s one that you can win. By working smart and safe, you can have a lawn and garden that are safe and free of pesky weeds. If you have any questions, feel free to contact the experts at LawnStar.
Take pride in your lawn. There’s a new era in lawn care and you’re on the cutting edge.
Follow these tips for a safe and effective tree removal
ThoughtCo / Nusha Ashjaee
- B.S., Forest Resource Management, University of Georgia
Homeowners usually welcome trees on their property. But some trees are invasive species that, over time, can take over a garden. Other trees may overwhelm your home, digging roots into the foundation or limiting access to light.
Whatever the reason, if you’re ready to kill a tree, you’ll need to review your options and make an informed choice about the best method for your situation. If you’re concerned about chemicals or are removing a tree in an area where you grow fruits or vegetables, you might choose to physically remove the tree. If you’re comfortable using chemical herbicide, however, a number of options are available.
Chemical herbicides are effective and relatively low cost. On the other hand, they involve using potentially harmful substances in your own backyard. There are ways to mitigate the risk, but you might prefer to avoid chemicals altogether. In that case, you have two options for tree removal: cutting down or starving the tree.
Cutting Down a Tree
If you’re removing a very large tree or are uncomfortable using a chainsaw, you can hire someone to take down your tree. Many people, however, simply cut down their own trees. Once the tree has been cut to a stump, you’ll need to grind the stump to the ground.
Unfortunately, cutting and grinding might not be enough to kill your tree. In some cases, trees will continue to sprout from the stump. If this happens, you’ll need to systematically look for new sprouts and cut them down whenever they appear. By cutting the sprouts, you deny the roots the energy they need to continue to grow.
If neither grinding the stump nor cutting sprouts is enough to kill your tree, you’ll have to dig down and painstakingly remove the roots from the soil. The notorious buckthorn bush/tree is an example of a species that can be killed only by completely removing the roots.
Starving a Tree
The bark of a tree is a system for transporting soil nutrients and moisture to the branches and leaves. With some trees, fully removing the bark around the circumference of the tree’s trunk will effectively starve it to death. This technique, called “girdling,” often is effective, but it isn’t foolproof. In some cases, trees can bypass or “jump” the girdle.
To get the best results, remove all layers of bark in a circle around the tree, cutting about 1.5 inches deep with a hatchet or ax. The girdle will need to be about 2 inches wide to kill a small tree and up to 8 inches wide for a large tree.
Chemically Killing a Tree
Herbicides can kill trees and, properly applied, be safe for the environment. The most environmentally friendly options involve applying herbicide to a specific area of the tree. In some cases, however, the only viable option is to use herbicidal spray. There are five major types of herbicides, only some of which are rated for home or crop use. Triclopyr amine and triclopyr ester are growth regulator-type herbicides, while glyphosate and imazapyr kill plants by interfering with the synthesis of plant proteins. Aminopyralid is primarily effective on legumes such as kudzu and may not be appropriate for your needs. Here are six ways to chemically kill a tree:
- Cut Surface Treatments: This technique involves creating a pathway through the bark so that herbicide can be introduced into the plant’s vascular tissue. Start by making a series of downward cuts around the circumference of the tree with an ax or hatchet, leaving the frill (cut section of bark) connected to the tree. Immediately apply the selected herbicide into the cuts. Avoid spring applications when sap flowing from the wound will prevent good absorption.
- Injection Treatments: Use specialized tree injection equipment to administer a specific amount of herbicide into the tree when the cut is made. Treatments are effective when injections are made every 2 to 6 inches around the tree. For best results, treat trees 1.5 inches or more in diameter at chest height. Injection is often handled by a tree removal company because it requires an investment in equipment.
- Stump Treatments: After cutting a tree down, you can minimize the possibility of regrowth by immediately treating the freshly cut surface with herbicide to prevent sprouting. On larger trees, treat only the outer 2 to 3 inches, including the cambium layer, of the stump (the internal heartwood of the tree is already dead). For trees 3 inches or less in diameter, treat the entire cut surface.
- Basal Bark Treatments: Apply herbicide to the lower 12 to 18 inches of the tree trunk (on the bark) from early spring to mid-fall. Some species can be treated during winter. Use herbicide spray mixed with oil until the bark is saturated. The low-volatile ester formulations are the only oil-soluble products registered for this use. This method is effective on trees of all sizes.
- Foliage Treatments: Foliar spraying is a common method of applying herbicides to brush up to 15 feet tall. Make applications from early summer to late September, depending on the choice of herbicide. Treatments are least effective during very hot weather and when trees are under severe water stress.
- Soil Treatments: Certain soil treatments applied evenly to the soil surface can move into the root zone of targeted plants after ample rainfall or overhead moisture. Banding (also called lacing or streaking) applies concentrated solution to the soil in a line or band spaced every 2 to 4 feet. You can use this type of application to kill large numbers of trees.
Before starting a tree removal project, learn how to use herbicides safely and legally. Herbicide treatments of roots or soil (or sprayed herbicides) can kill vegetation unintentionally.
You want to apply pre-emergent herbicide to your lawn. Maybe you’ve done it before and maybe not. Either way, you’ve got questions. And, you’re in luck because we have answers. Use this guide to learn the right way to apply pre-emergent to your lawn and get rid of that pesky crabgrass.
What is Pre-Emergent?
Pre-emergent herbicide is a lawn care product designed to prevent undesired weeds. A pre-emergent chemical solution may contain one or more of the following active ingredients:
- Benfluralin – a dinitroaniline herbicide developed to inhibit root and shoot development to prevent weed growth in lawns, crops, and ornamentals.
- Dithiopyr – a mitotic herbicide developed to inhibit weed root growth in lawns, vines, and ornamentals.
- Isoxaben – a benzamide and isoxazole herbicide developed to control broadleaf weeds in vineyards and nut tree orchards.
- Oxadiazon – a dinitroaniline herbicide developed to control the growth of broadleaves, grasses, sedge, bush vines, and bramble.
- Pendimethalin – a dinitroaniline herbicide developed to inhibit cell-division and cell elongation to destroy or prevent weed growth in crops, lawns, and ornamentals.
- Prodiamine – a dinitroaniline herbicide developed to control weeds in crops such as soybeans, alfalfa, cotton, and ornamentals.
- Siduron – a dinitroaniline herbicide developed to prevent weeds when seeding or overseeding a lawn.
- Trifluralin – a dinitroaniline herbicide developed to control a variety of annual grass and broadleaf weeds in tree fruit, nut, vegetable, and grain crops.
So, precisely what does pre-emergent do? In a nutshell, it prevents the growth of undesired plant life before it sprouts.
How Does Pre-Emergent Work?
Depending on the formula used, pre-emergent works in one or more of three ways:
- Inhibits plant root growth
- Inhibits seed cell division
- Inhibits specific enzymes essential to the growth of certain plants
As you can see from the previous list, most pre-emergents have dinitroaniline herbicides. And, these chemicals do not prevent seed germination. Instead, they primarily inhibit the growth of roots. So, younger plants are more susceptible to damage.
Using pre-emergent on a newly-seeded lawn, in most cases, is not a wise idea. Many pre-emergents can potentially kill newly-sprouted grasses.
Does pre-emergent kill weeds?
Pre-emergent is not meant to destroy existing weeds or their seeds. The herbicides will kill weeds as they begin to sprout from their seeds. However, seeds that remain dormant will not be affected by pre-emergent application.
Does pre-emergent kill crabgrass?
As with weeds, yes, pre-emergent can kill crabgrass as new seeds germinate. Yet, it is not able to destroy established crabgrass. Instead, it is best to manually remove mature crabgrass from your lawn.
[Crabgrass seedlings look like miniature corn stalks. Mature crabgrass has wide leafblades: 1/4″ wide or more. .]
Are Pre-Emergents Safe?
Pre-emergents must be used as advised. According to the FTC, “United States law requires that herbicides and fungicides undergo a rigorous registration process with the U.S. Environmental Protection Agency (“EPA”) before they may be used or sold in this country.” So, as long as you follow the instructions, pre-emergents sold in the US are considered safe.
When to Apply Pre-Emergent Herbicide?
It’s important to know when to spray pre-emergent or apply granular herbicides. Using these chemicals in the wrong temperatures can render them ineffective.
Ideal Times of Year for Application:
Now, what is the right month to apply pre-emergent? While there are ideal application times, pre-emergents can be applied throughout the year. Fall application should take place in late summer or early autumn. Spring application should be early in the season. The key is to apply the product before unwanted seeds germinate.
Best Temperatures for Application:
Next, what temperature should it be to apply pre-emergent? Some landscape specialists claim that the temperature should be 60 or 70 degrees (F). But, a study from The University of Missouri College of Agriculture, Food, & Natural Resources found that the most effective time to apply pre-emergent herbicides was when the ground has been 55 degrees (F) for 5 days in a row. So, watch the weather and plan your application in advance.
How Do You Use Pre-Emergent? (Step-by-Step)
Note: For proper application, you want to follow the manufacturer’s instructions. But, as a rule, here’s how to properly apply both granular and liquid pre-emergent.
How to Use Granular Pre-Emergent Herbicide:
- Pour granular pre-emergent herbicide into a spreader.
- Apply the grains uniformly, at a rate of 1.5 to 6 pounds per square foot per year, across the area of lawn to be treated.
- Follow-up with at least ½” of water via sprinkler irrigation or rainfall within 14 days.
How to Use Liquid Pre-Emergent Herbicide:
- Pour liquid pre-emergent into a sprayer.
- Spray evenly, at a rate of 2-6 quarts per acre per (no more than 12 quarts per acre per year) across the area of lawn to be treated.
- Follow-up with at least ½” of water via sprinkler irrigation or rainfall.
What Are the Most Common Mistakes People Make?
Here’s what you want to avoid when you apply pre-emergent herbicide to your lawn.
- Applying to newly-overseeded turf. You should wait at least 60 days after overseeding or until after the second mow before applying pre-emergent.
- Laying newly-set sod over pre-emergent. It is recommended to wait until at least a year after applying pre-emergent herbicide to lay sod.
- Applying to damaged turf. Do not apply to turf that has been affected by drought, low fertility, or pest damage.
- Aerating turf too soon after application. While treating your lawn with pre-emergent, do not aerate or thatch.
- Applying to putting-greens. Golf courses find that pre-emergent laid on frequently-used putting greens is ineffective.
- Using an irrigation system to apply. Running herbicides through your irrigation system can be harmful to livestock and other living organisms that are crucial to a healthy ecosystem.
- Not watering after application. Water is required after pre-emergent herbicide application to move the product below the ground’s surface to the area of seed germination.
- Using pre-emergent and fertilizer at the same time. The amount of water needed to fertilize a lawn will move pre-emergent too far below the ground’s surface and render it ineffective.
- Using the wrong type of chemical for your grass species. Most herbicides are specifically formulated for certain species of turf and weeds.
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Keep weeds out of your vegetable garden with the right herbicides formulated for use on your edible garden plants. Weed killers will help you take control of your weed problem, eliminating weed pulling and extra work in your gardening chores. It is important to use herbicides labeled for use on edible plants, so you can safely harvest and enjoy vegetables.
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Herbicide Weed Killer for Edible Gardens
There are many options available when it comes to choosing the right weed killer for your edible garden plants. Pre-emergent products work by killing weeds before they grow above the ground by targeting weed seeds under the soil. They must be applied at the right time of year to be effective, which is usually in the spring when temperatures reach 55 degrees. Post emergent products can be applied to weeds already up and growing in your yard, and can be used throughout the year.
Make sure to read the label on products carefully to make sure the product can be used on or around your plants, and that the weeds you want to kill are also listed on the label. Apply products carefully, and take note if there is a time period from application to harvest, so you can be sure your produce is safe to eat.
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We sell professional do it yourself pest control (diy), exterminator and
extermination insecticide, pesticide, chemical and bug killer treatment
products to spray, eliminate and exterminate pests.
Many of our products are not available in stores
such as Home Depot, Walmart or Lowes.
Patrick McCullough, Extension Turf Weed Scientist, University of Georgia
This is is a common question many turf managers will be asking before herbicide applications this summer. Responsible pesticide applicators will always read and follow label directions before applying any product. However, there is often confusion regarding the language on labels about this issue. Many herbicide labels will contain a statement such as “Do not apply when temperatures are above 90° F”. These disclaimers are usually included on labels to limit the liability of chemical companies when turf managers apply their products during summer heat. This disclaimer is often unaccompanied by anything else to explain or clarify the effects of temperature on potential herbicide injury on turfgrasses.
Turf managers who carefully follow label instructions will see these disclaimers and may hesitate before applying herbicides. Others will question the exact interpretation of these warnings. Examples of questions often asked include the following.
Is it safe to apply herbicides if:
- temperatures are below 90° in the morning but above 90° in the afternoon?
- temperatures are below 90° this week, but rise above 90° next week?
- temperatures are above 90° now but are forecast to drop to the 80s?
- the temperature is 89.9° and the label says do not apply at 90°or above?
Unfortunately, there are no correct (or incorrect) answers for these questions. Herbicide applicators must evaluate their turf and factors that may increase turf injury. Several factors turf managers should consider when applying herbicides in summer include:
- Turfgrass species
- Turfgrass stress
- Herbicide chemistry
- Weed species and population
- Past performance of herbicides
Turfgrass species is a major factor in determining tolerance to herbicide applications. The overall sensitivity level of a species should be evaluated before herbicide applications and closely monitored when temperatures are high. For example, bermudagrass and tall fescue are both labeled for treatments with sulfentrazone (Dismiss). Tall fescue is naturally more sensitive than bermudagrass to sulfentrazone and rates must be reduced to account for lower tolerance levels. Turfgrasses that are sensitive to herbicides under good growing conditions may be more susceptible to injury during periods of heat stress and other herbicide chemistries should be considered.
As temperatures exceed 90° F, cool-season grasses become stressed and consumption of carbohydrates exceeds production through photosynthesis. Thus, grasses such as tall fescue with good tolerance to herbicides during active growth may be naturally more susceptible to herbicide injury during periods of physiological stress. Warm-season grasses grow more efficiently than cool-season grasses under these temperatures and generally have minimal stress when water is not lacking. Uninhibited growth of warm-season grasses at higher temperatures may be attributed to better tolerance to herbicide applications in summer relative to cool-season grasses. However, herbicide tolerances for specific species are all dependent on the chemistry of the product applied.
Effects of temperature on herbicide activity
Turf managers must also understand potential effects of temperature on herbicide activity. Many herbicide chemistries, such as synthetic auxins, have greater activity at warm temperatures compared to use during cooler weather. For example, Trimec Classic (2,4-D + dicamba + MCPP) applications often have erratic activity in early spring but perform much more effectively in summer. Sensitive species to these herbicides, such as St. Augustinegrass, have a higher risk of injury due to greater activity under excessive heat. Switching to another chemistry, such as a sulfonylurea herbicide, may be a safer option especially at reduced label rates. Enhanced activity of herbicides during these periods may also allow end-users to reduce rates and applications required to achieve desirable weed control.
Targeted weed species and the benefits of control should also be considered before risking turf injury from herbicide use in hot weather. Warm-season weeds that spread laterally, such as spotted spurge or knotweed, will continue to grow during hot temperatures and out-compete turfgrasses for light, water, and nutrients. If continued growth of weeds may result in loss of the overall turf stand, practitioners should consider applying herbicides. Preventing annual weeds from taking over a turf area during summer may help reduce voids in early fall that may allow winter annual weeds to establish. Thus, turf managers must evaluate the risk of turf injury at the expense of weed control and potential implications in long-term management.
Previous turf injury from herbicide applications during moderate temperatures may indicate risk of greater injury during excessive heat. Similarly, past reports of turf safety under high temperatures may suggest a specific product has potential for use under local conditions. It is recommended for turf managers to record air temperatures, soil temperatures, relative humidity, turf health, and other environmental factors that may influence turf tolerance to herbicides. These records can be referenced to plan future spray programs for mid to late summer in subsequent years.
Other environmental factors influence turf injury from herbicides in summer. While temperature is an important factor, high humidity increases absorption of many herbicides compared to low humidity levels. Herbicide applications in early evening when humidity and temperatures decline may help reduce injury potential compared to midday when these levels are higher. However, subsequent heat and humidity may influence turfgrass translocation and metabolism of herbicides that could also limit tolerance levels after applications.
Unfortunately there are no perfect application programs or predictive models to determine safety of herbicides on labeled turfgrass species. It is recommended to spray a test area and evaluate turf injury before making broadcast treatments during periods of excessive heat. Furthermore, if there is uncertainty over making herbicide applications turf managers should wait and assess the benefits of potential weed control. Applicators may wish to consult local extension agents for further information regarding herbicide applications during summer months.
Please share this information with others in the landscape & turf industry. For more information:
Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office
www.georgiaturf.com has a section on identifying weeds under Pest Management and weed control recommendations under the Turfgrass Pest Control Recommendations. (Follow all label recommendations when using any pesticide)
You can also find weed control recommendations in the Pest Management Handbook (Follow all label recommendations when using any pesticide)
Helping Nebraskans enhance their lives through research-based education.
Asparagus Weed Control
submitted by Sarah Browning, UNL Extension Educator
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Asparagus Weed Control: Controlling weeds in a home or acreage asparagus planting can be difficult, but it is a necessary step toward maintaining a high-yielding planting. Since asparagus is a perennial crop, it’s not possible for home gardeners to till or plow the planting area to eliminate weeds. However, there are several other techniques that can help to successfully control problem weeds.
Asparagus overwinters each year as a dormant crown of roots, with all the summer’s foliage and stems dying back to the crown. If planted correctly, the crown is initially located approximately 6-8 inches deep in the soil, but it will grow each year enlarging in both width and height; meaning that an asparagus crown can expand upward in the soil profile over time. It’s important to keep this depth in mind and the fact that no living growth remains above ground during the dormant season as we look various methods of control.
Mechanical Control: In small plantings, mechanical removal of weeds can be accomplished by hoeing. This is easy to do in early spring, before new spears begin to emerge, without danger of damage to the plants. In larger plantings very shallow tilling, only about 3 to 4 inches deep, will help eliminate weeds in early spring before new growth begins.
Cultural Control: Mulch, in conjunction with hoeing or tilling, helps maintain your weed control. Apply 3 to 4 inches of an organic mulch, such as wood chips, grass clippings, compost or clean straw. It will prevent germination of new weeds, minimize soil temperature fluctuations in summer and help preserve soil moisture.
Herbicidal Weed Control: Applications of a pre-emergent herbicide can be used to control annual weeds, like crabgrass and foxtail, in the asparagus planting. One product, which has the added benefit of being organic, is corn gluten meal and can be found in Preen Vegetable Garden Weed Preventer, as well as other products. Corn gluten meal is a by-product of corn processing and contains 10% nitrogen, along with its pre-emergent properties. Apply it every four weeks at labeled rates throughout the asparagus planting, but be careful not to apply it to other areas of the vegetable garden where you will be planting seeds.
Post emergent weed control can be achieved with glyphosate and paraquat, both non-selective herbicides with no soil residual activity that can be used in asparagus. Glyphosate is systemic and works best at controlling perennial weeds. It can be broadcast over the entire planting area in early spring before new asparagus grown emerges or after the last harvest. Snap all spears 1/2 inch below the soil line, so no spears are above ground, then overspray the planting area.
Paraquat is a contact, non-systemic herbicide that kills the growing shoots of weeds. It works best for controlling newly emerging annual weeds in early spring before your asparagus has started to grow.
When using herbicide, always read and follow the label directions for personal protective equipment and application rates. Pay special attention to the pre-harvest interval, or the amount of time you must wait after a pesticide application before harvesting again.
Do Not Use Salt!: An old recommendation for asparagus weed control involved the application of salt, by pouring the salty water from an ice cream maker on the asparagus patch. This provided some weed control because asparagus is deep-rooted and has a higher sodium tolerance than some common weeds. However, salt quickly destroys soil structure resulting in pour water penetration in the soil and will eventually kill the asparagus, too, or move out into nearby sections of your vegetable garden and kill other less salt tolerant vegetables.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
Learn how to use household table salt to kill stubborn weeds.
Wega52 / Getty Images
Dealing with weeds in the garden is a task that most gardeners have come to dread. Pulling them by hand is time-consuming and repetitive, but many gardeners also want to avoid using commercially available chemical herbicides as they pose both environmental and health risks.
That being said, there are some non-toxic herbicides that can be used to effectively control weeds in the garden—namely, table salt. While no herbicide can ever be labeled as truly ‘harmless’ in the garden (their main purpose is to kill unwanted plants after all!), salt (or sodium chloride) is a natural solution that works well on pesky weeds.
Can Salt be Used to Kill Weeds?
In short, salt is an effective non-toxic herbicide. However, not all salt is created equal when it comes to weed control. Regular iodized or non-iodized table salt must be used. Check the package to ensure you are using sodium chloride, not magnesium sulfate (Epsom salts), rock salt, or sea salt.
When using salt as a herbicide it must be applied carefully. It can easily kill surrounding plants, or leech into the soil and affect its long-term health. Too much salt can even sterilize the soil over time. As such, it may be most effectively used to treat weeds that are not surrounded by plants that you care about in the garden, such as weeds that are poking through cracks in asphalt or pavement, or growing between patio stones.
The Chemistry of Salt: How Salt Works to Kill Weeds
Salt (sodium chloride) works to kill weeds by dehydrating the plants and disrupting the internal water balance of the plant’s cells. Since salt is water-soluble, it is most effectively applied when mixed with water as this makes it easier for the weeds to absorb. Sodium chloride is highly toxic to all plants, which is why caution must be taken in its application. In general, salt is best used as a herbicide for small-scale gardening or weed control.
How to Use Salt as a Herbicide
Salt is most effective as a herbicide when it is mixed with water. The recommended strength of the saltwater mixture depends on where you plan to apply the herbicide. If you are applying salt to weeds in a garden bed with other plants that you don’t want to kill, you should start with a weaker mixture—such as a 1:2 mixture of salt and water.
Alternatively, if you are applying the salt in an area where the long-term health of the soil is not an issue (like between patio stones, cracks in driveways, etc.) a much stronger mixture can be made such as a 2:1 or 3:1. This amount of salt will definitely affect the pH levels of the soil over time and may cause it to become sterile.
Saltwater solutions should be applied directly to the foliage of the weed. Avoid soaking the roots with the mixture to protect the surrounding soil and plants. The saltwater can be applied using a spray bottle, or it can be poured from a container. If there are other plants nearby, water them generously after applying the herbicide to the weeds to flush out any saltwater that made it into the surrounding soil.
Salt vs. Other Non-Toxic Herbicides
There are several other ‘non-toxic’ herbicides that are popular among home gardeners. Each has its own benefits and disadvantages, and no one option is a one-size-fits-all solution.
White vinegar is one option, although it has been proven over time to be ineffective on its own. However, when mixed with salt and water, vinegar controls weeds well. As with the salt and water mixture, vinegar must be applied carefully as it can change the pH balance of the soil over time—affecting the growth of future plants.
Boiling water can also be used to some degree of effectiveness. It is a great option for dealing with clusters of difficult weeds in a garden bed, as the water will have no residual effects on the soil. However, as with most other herbicides, boiling water needs to be applied to the garden very carefully so as to not damage plants that you don’t want to kill.
Surprisingly, fire is another method of ‘non-toxic’ weed control that is used by gardeners. The fire burns the emerging weeds, causing damage at a structural level. While fire control will permanently remove annual weeds, it does not kill the roots of hardier perennial weeds. Flame weeders can be purchased online or at most garden centers or nurseries.