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Knotweed Control

How to Get Rid of Knotweed

We here at Solutions Pest and Lawn are huge, HUGE fans of knotweed....NOT! Truthfully, we can’t stand knotweed and neither can any of our customers who have complained about knotweed and have asked us for tips on how to control such a pesky and difficult-to control weed.

Knotweed originated from Europe and has firmly established itself now in the States, creeping up everywhere--field crops, row crops, orchards, yards, gardens and turf. So just how do we get rid of this blasted weed? We have just the guide for you below on identifying knotweed and the best methods of controlling knotweed..

Shop the best products for knotweed control by browsing our selection below. Scroll further to learn more about knotweed and how to eradicate it from your yard and property the right way.

For more information on controlling knotweed on your lawn and to get advice catered to your unique issue from experts, contact us at askapro@solutionsstores.com or call our customer service line at (800) 479-6583.

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How To Get Rid of Knotweed: Solutions 4 Step Process

Step 1: Identification. Prostrate knotweed is an annual weed that likes to grow in the early summer. This invasive plant develops slowly by by mid-summer it is easily noticable. The interesting thing about knotweed is that it grows laterally rather than vertical hence why it could overtake a space and be an eye sore. Mature knotweed form mats of slender stems which are sollen at the nodes. The flowers are very small and inconspicuous. Based on its appearance, knotweed can often be mistaken for other weeds like spotted spurge or purslane but there are slight difference in the leaf arrangement and traits of the leaves.

If you are having trouble ID'ing the weed on your lawn as knotweed, you can always send us a photo of the weed via email at identification@solutionsstores.com. We have experts on staff which can accurately identify the weed and then refer you to the best products for its control.


Step 2: Inspection. Mid-summer is the best time to conduct a knotweed inspection. Look for it next to driveways and sidewalks as it can push out towards there. As the knotweed matures, it becomes tough, wiry and prostrate and develops a thin taproot which if you can discover early and digout and handpull will make successfully eliminate the knotweed. However by the time the weed is noticably by midsummer it may be too late to be able to do this.


Step 3: Control. If knotweed has already emerged, 2,4-D or Triclopyr has shown to do a good job in controlling knotweed. In some cases where the knotweed is stubborn and persistent, a combination of products may need to be used to get better postemergence control. Mix a combination of herbicides into a pump sprayer and spray and adequate amount all over the knotweed. Within a few days it will start to show signs of wilting and death and before long it will be eliminated. For pre-emergent control, Isoxaben has shown to be effective to keep knotweed from germinating in the spring time.


Step 4: Prevention. The best way to prevent knotweed from making a return and taking over is to grow healthy turf grass that will choke out any weed attempting to grow. Address compacted soil issues by reducing foot traffic on your grass. Applying mulch is another good preventative measure against prostrate weed in vegetable gardens. Coat the entire garden bed with polethylene mulch and cut holes enough for watering around the plant.


Learn More About Knotweed

Knotweed (polygonum species) are herbs, also known as smartweeds. Knotweeds are becoming increasingly common in the states such as Florida where about 15 species occur. Some are exotic while others are native. Knotweeds spread by creeping rhizomes and seeds. They grow in marshes and swamps, wet areas and ditches, just about any wetland situation. They occur year round. A distinguishing characteristic of knotweed is its swollen nodes where the leaves meet the stems. Leaves are lanced shaped, narrow and willow-like.


The leaf bases form sheaths that surround the stem and leaves are alternately attached. Knotweed flowers are small and pinkish or whit. Flowers grow in terminal spikes that typically are several inches long.


Common knotweed are usually also seen on the edges of fields and in areas where nothing else is growing. Common knotweed is a low to the ground spreading annual weed where it'll start in just a small little area and they'll be a plant or two. Pretty soon you may have a whole driveway full of it or you may have a whole bare spot out in the field full of common knot weed in a short period of time.


Have Some Grassy Weeds You Want Gone? View Our Grassy Weed Control Section


Origin and World Distribution

Prostrate knotweed is one of the most widespread weeds found worldwide. Its widespread distribution can be attributed to a number of different factors including high genetic polymorphism, high phenotypic plasticity, prolific seed production, multiple means of seed dispersal, formation of a persistent seed bank, and allelopathy.

Prostrate knotweed is believe to have originated in Europe. It was likely introduced to North America by the first colonists who sailed over here and was first collected in Canada in 1821. One theory is that knotweed was introduced as a contaminant in agricultural seeds. Today, knotweed is found in all 50 of the United States.


How Knotweed Thrives

A single common knotweed plant may produce 125 to 6,400 seeds, depending on resource availability. In Pennsylvania, early-season seed crops were greater than late-season seed crops, though some seeds were produced throughout the growing season . In North Dakota, 2 prostrate knotweed plants collected in different years produced 4,600 seeds and 6,380 seeds.

Prostrate knotweed seeds are dispersed by birds, mammals, and water . Its seeds may also be dispersed by vehicles or other mechanical means. Prostrate knotweed seeds may contaminate crop seeds and be spread upon planting. They may be ingested and spread by livestock  or through the spreading of cow manure. Prostrate knotweed seeds were found floating in irrigation water in Nebraska  and Washington.


Knotweed thrives in any moist soil or river cobble, in full or partial sunlight. Knotweed is known to be most common in the flood plains along side rivers and creeks. It also grows in road-side diteches, waste areas and beaches.


Have A Lawn Issue That Isn’t Knotweed ? Check out Our Lawn Care Main Category!


Why Is Knotweed Such a Threat?

Knotweed is fast growing and extremely aggressive. It invades river and creek banks, permanently displaces native vegetation, destroys critical fish and wildlife habitat and reducees recreational opportunities. Due to a huge and vigorous root system, large patches are very difficult to keep under control. Seasonal flooding continues to spread knotweed throught many northwest watersheds. Knotweed is an aggressive and destructive weed that spreads quickly, shades out native plants and destroys habitat. That is why if you see knotweed growing on your property you need to act quickly or it will get beyond your control.


How To Control Knotweed

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Controlling knotweed doesn’t just mean spraying some herbicide here and there and that it--this will involve a change in lawn maintenance habits to make for a healthier lawn where knotweed will be less likely to grow. This would be achieved best by aerating your lawn and making sure the soil is
well fertilized. Implementing these sort of maintenance options in your routine will make knotweed and many other weeds unable to compete.

If it isn’t too late to apply pre-emergent, treating your lawn with Dithiopyr 40 WSB or Prodiamine 65 WDG work best to control knotweed. Knotweed is an annual that germinates in late February or early March, so the best time to apply these pre-emergent herbicides should be in the late fall. However, if it is too late and the knotweed is out and about, you should use a post-emergent herbicide instead.


Better Safe Than Sorry: Equip Yourself With Protective Safety Equipment Before Spraying

Recommended Post-emergent Options

When it comes to post-emergent herbicides, we recommend Glyphosate 4 Plus Weed Killer Concentrate, 2 4-D Amine Selective Weed Killer or Trimec Southern Broadleaf Herbicide. it’s best to apply them when the knotweed is fairly young for more effective control. Common knotweed seed germinates in the heavy rains of spring. Its long taproot helps it survive the dry heat of summer.A more mature knotweed may be more resistant to herbicides and thus it may take repeated applications for the weed to be eradicated.


Make Sure You Have The Right Equipment For The Job. SHOP For Sprayers and Other Lawn Care Essentials

Knotweed Tips and Recommendations

  • Granular treatments that prevent seeds from germinating will help stop most weed growth, but once the seed sprouts, spot treatment sprays are most effective.

  • Use a hand-pump sprayer with a thin tip nozzle. Spraying a fine mist is best when applying herbicides to ground ivy.

  • When applying herbicides be sure to wear protective clothing or safety equipment that completely covers your arms and legs, as well as gloves, socks and shoes. Avoid inhaling the spray or getting it in your eyes or mouth. 

Additional Knotweed Resources:

Common Knotweed Management Guidelines--UC IPM

Prostrate Knotweed (A) (Polygonum aviculare) - family: Polygonaceae

Knotweed, Prostrate — Center for Turfgrass Science — Penn State


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