Elisabeth C. Miller Library

Gardening Answers Knowledgebase

Search Results for: Weed control | Search the catalog for: Weed control

Plant Answer Line Question

Keywords: genetically modified seeds, Weed control, Herbicides

What can you tell me about the weed killer "Concern Weed Prevention Plus"?


This product is corn-gluten based, and it is not meant to work on weeds which are already growing, but on those which have yet to emerge (pre-emergent). Corn gluten meal has been promoted as an environmentally safer alternative to conventional herbicides, but there are still certain issues that bear considering. Research at Oregon State University showed that corn gluten meal did not prevent weed seed germination. Here is an excerpt from the study's findings:
"Corn gluten meal did not control any weeds in any trials under any circumstances over a two-year period. They found no evidence of pre- or post-emergence weed control in any of their trials. Because it contains 10 percent nitrogen, corn gluten meal proved to be a very effective fertilizer, causing lush, dense growth of turfgrass and of weeds in shrub beds."

Although corn gluten meal presents far fewer risks to human and animal health than conventional herbicide, a gardener who is attempting to use only organic methods might consider the source of the corn in these products, which is very likely to be genetically modified. A webpage no longer available from University of Wisconsin Master Gardeners addressed this question:
"Up to 60% of the commercial corn and soybeans in the United States is grown from GMO seed. Corn gluten sold as a preemergent herbicide may indeed contain GMO corn, but it has not yet been tested. Here's the twist. Corn gluten can reduce the need for traditional herbicides that have environmental side effects. It likely now contains GMO corn. It could be produced from non-GMO corn, but would likely be more expensive."

Washington State University professor of horticulture Linda Chalker-Scott has also written about "The Myth of Weed-Killing Gluten," and states that no research suggests this is an effective method of weed control in the Northwest. She recommends sub-irrigation, mulch, and soil solarization instead.

Date 2018-08-15
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Plant Answer Line Question

Keywords: Weed control, Lawns--Care and maintenance

I am renovating a lawn that has been completely ignored for a long time--dandelions 3 per square foot, for example. I need to know if I should use something like weed-and-feed now to kill the 1000s of weeds and wait till spring to aerate, remove the top 1/2-inch of the lawn, fertilize and re-seed. Do I need to get on this before the first frost?


Regarding your questions about lawn renovation, I have found a few options for you:

1. If the weed-and-feed product is for pre-emergent weeds, this would not work on your lawn, which already has dandelions growing actively. If the product is post-emergent, it will kill the dandelions, but if you are planning to sow grass seed, you will need to wait before sowing (different products have different guidelines, so check the directions on the package carefully). According to The Lawn Bible (by David R. Mellor, 2003), you should also make sure that the herbicide will target the weeds you have. Do not spray in windy conditions, and only treat areas which need it.

Overuse of herbicide destroys valuable bacteria and insects in the soil, so prevention is the best: mow the lawn high, which will keep weeds from getting established, as they need light to thrive; don't scalp the lawn; water only when it is too difficult to press a screwdriver into the top 2 inches of the soil.

2. There are less toxic alternatives. Some sources say that corn gluten prevents weed seeds from sprouting. They must be wet to be activated. (It won't work on dandelions which are already thriving in your lawn.) Please note that subsequent research suggests corn gluten may be ineffective as a weed control method. See this Oregon State University study.

According to Ann Lovejoy's book, The Handbook of Northwest Gardening, corn gluten should be spread at a rate of 20 pounds per 1,000 square feet of lawn. Do this two or three times a year (in spring and fall, with a summer booster as needed). For ongoing weed suppression, apply it in small amounts whenever you pull up weeds (make a paste of corn gluten and water).

3. The Lovejoy book also has a recipe for fall lawn renovation:
a. Mow the existing grass as short as possible.
b. Spread 1 inch of clean crushed quarter-ten gravel (not pea gravel) evenly over the entire surface.
c. Spread 1 inch of compost over the gravel.
d. Top-seed with a regionally appropriate blend if the lawn is thin and spotty.
e. Wait 6-7 weeks before mowing again.

A criticism of weed-and-feed products is that they will add excessive amounts of phosphorus to your lawn, which will actually encourage weed growth once the herbicide breaks down.

The Northwest Center for Alternatives to Pesticides has good information about controlling dandelions without using weed-and-feed products (originally published in the Journal of Pesticide Reform, Fall 2001).

Toxic-Free Future (formerly known as Washington Toxics Coalition) has information on an overall approach to weed control and lawn care

Date 2019-05-22
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Plant Answer Line Question

Keywords: Symphytum officinale, Weed control

Comfrey root has taken over my acreage at my home. I want to know how it spreads, how to kill it, naturally and chemically, by the root. I am currently using Roundup sporadically. I don't know how it got into my yard or anything. I would like to be able to kill it off and plant nice grass there in the spring.


Comfrey (Symphytum officinale) has a fibrous root system which is very deep and difficult to eradicate. Any bits of root left in the soil can produce new plants. While it may be tempting to take the quick path and use RoundUp to get rid of your comfrey, you may want to consider the health and environmental consequences of this product, whose active ingredient is glyphosate. Northwest Coalition for Alternatives to Pesticides has information about this chemical.

If you avoid using herbicide, you may find additional uses in the garden for the comfrey you remove by hand. Do not rototill this plant, and always wear gloves when handling it. Dig carefully and remove as much as you can of the roots, and then dispose of them. Pacific Northwest gardener and author Mary Preus writes about comfrey in The Northwest Herb Lover's Handbook (Sasquatch Books, 2000):

Comfrey can play an important role in compost making, The considerable leaf mass of a mature comfrey plant, cut several times in a season, can add plenty of high-nitrogen green material to the pile. In addition, the leaves contain calcium, phosphorus, potassium, and trace minerals drawn deep from the subsoil. Just be sure there are no ripe seeds, and that no pieces of root are attached to the base of the leaves that go into the compost pile.

The leaves can also be added to potato crops as a fertilizer. After allowing them to wilt, you can use the leaves by chopping them up and placing them in a trench with main crop potatoes. As the leaves are high in potassium, they make an excellent fertilizer. Layer to a depth of 1 to 2 inches. Comfrey can also be used on other plants that benefit from high doses of potassium, like tomatoes and runner beans. It has also been used to as a top dressing around soft fruit bushes. As the leaves break down, gently cultivate them into the planting area. There is an article from the Permaculture Research Institute about the uses of comfrey, The Wonderful Multi-purpose Comfrey Plant, by Melissa Miles (October 1, 2010).

If you have large swathes of your garden which are weedy, you can also try sheet mulch as a solution. StopWaste.org has information on how to do this. To simplify, the technique is to spread out a layer of cardboard or newspaper (at 4-6 sheets thick) and cover it with a layer of organic mulch (compost, straw, alfalfa hay--available at feed stores, woodchips, coffee grounds, etc.). Then wait 6-8 months. This is not an exact science because there are many variables, such as thickness of newspaper, type of mulch and what type of plant you're trying to kill. Perennial weeds and especially coarse grass will push through the cardboard once it starts to break down so it is critical that if and when this happens you pull the mulch back and put down more newspaper/cardboard, and then replace the mulch.

Date 2019-05-17
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Plant Answer Line Question

Keywords: Weed control, Integrated pest management

I have a smaller lawn, in a slightly shady area and have been having problems with dandelion and white clover. I don't mind a few weeds, but it is getting to be too many. Children and pets play on this lawn so I don't want to put anything that would be toxic to them on the lawn. What would you suggest I do?


Given that you are concerned for your children and pets, it makes sense to hand-weed your lawn. A little pocket knife is a great tool for doing this quickly and tidily. If you just spend a little bit of time at it a few days a week, it will go faster than you might imagine. Try to live with the clover; it is extremely difficult to eradicate, and it is great for honeybees.

Small dandelions are easier to pull out. The City of Seattle has excellent information about caring for lawns without pesticides, including hints about controlling dandelions. Look in the right-hand menu for additional links to lawn care information.

This article on Dealing with Dandelions from the Journal of Pesticide Reform (Fall 2001) describes several types of dandelion weeding tools.

Date 2018-11-07
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Plant Answer Line Question

Keywords: Weed control, Mulching

What is the best time of year to use Casoron and/or Preen for weed control on ornamental beds?


Both of these herbicides are registered pesticides, and the law requires that they be used in strict accordance with the directions (and only on the weeds/pests for which they are registered). It is safer for you and the environment if you manage weed problems without the use of pesticides.

You may wish to know more about these particular pesticides. Both Casoron and Preen are pre-emergents, meaning that they work to kill seedlings before they sprout. This means they will not eliminate weeds that have already broken through the soil surface and are growing above ground.

Casoron is persistent in both soil and water (i.e., it hangs around). Its active ingredient is dichlobenil. There are numerous environmental and health concerns associated with this chemical. Dichlobenil will kill any plants which are exposed to it, and will harm beneficial soil microorganisms. Below is a fact sheet about dichlobenil from Northwest Coalition for Alternatives to Pesticides.

The active ingredient in Preen is trifluralin. It is a suspected carcinogen, and is toxic to fish and aquatic life, and earthworms. Here is more information from Cornell University and Extension Toxicology Network UK.

The links below provide information about alternatives to chemicals for weed control. Northwest Coalition for Alternatives to Pesticides has a page of factsheets about specific weeds and ways to manage them. Here is their page on managing weeds in garden beds.

Toxic-Free Future (formerly known as Washington Toxics Coalition) also has information on ways to handle weeds in the garden. Here is more information in a PDF file.

Before reaching for chemical weed control, it makes sense to adopt gardening practices which will help keep the weed population low. Mulch is an excellent way to control garden weeds. After you manually remove weeds from an area of your garden, apply a layer of mulch. This should suppress weed growth and help retain soil moisture. Here is what garden expert Cass Turnbull says about mulch:

"Not only does mulch retain water, smother tiny weeds and weed seeds, and make it easy to pull new weeds, it is also harder for new wind-borne weed seeds to get a foothold.

"Mulch can be spread anywhere from 1 inch to 4 inches thick. The thicker it is, the more effective and longer lasting. Spread it thick in big empty spaces. Spread it thin around the root zones of shrubs to allow for sufficient air exchange, especially around shallow-rooted plants like azaleas and rhododendrons. And never let mulch stay mounded up in the base or the "crown" of a plant. It can cause crown rot on some shrubs and can kill them, even a year or more later."

Source: The Complete Guide to Landscape Design, Renovation, and Maintenance, Betterway Publications,1991.

Date 2018-11-07
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Plant Answer Line Question

Keywords: Poa, Weed control, Herbicides

Is there a preemergent to use on Poa annua grass in the lawn and if so what is the name and when should it be applied?


According to The Lawn Bible by David R. Mellor (Hyperion, 2003), your best defense against Poa annua (annual bluegrass) is to mow high (2 inches, usually) to shade out weed seedlings; aerate the soil to improve drainage, because weeds thrive in waterlogged soil; and let the surface of the soil dry out between waterings. If one were to apply preemergent herbicide, this would be done in late summer to early fall, but we strongly recommend that you avoid use of herbicides and pesticides in lawn care due to environmental and health concerns. There are effective non-toxic approaches to weed management. Northwest Center for Alternatives to Pesticides has useful information on maintaining a lawn without chemicals.

For another good discussion of this issue, you might want to refer to the book, What the Experts May Not Tell You about Growing the Perfect Lawn by Tom Ogren (Warner Books, 2004).

The University of California, Davis Extension has a document about the management of Poa annua, including specific information on the various herbicides that have been used to treat it but, as mentioned before, it is best to avoid the use of toxic chemicals in the garden.

Date 2018-08-15
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Plant Answer Line Question

Keywords: Weed control, Equisetum, Lonicera, Geranium, Cistus

What does "horse grass" look like? According to Ciscoe, it can't be gotten rid of and I want to see if this is what I have.


I wonder if you are referring to horsetail, or Equisetum, which is a very persistent weed.

Wikipedia has a picture, and here is another from CalPhotos

Here is an article on Field Horsetail and Related Species from Oregon State University Extension.

Here is what Ciscoe Morris said about this plant in the Seattle P-I (April 29, 2006):

"Hands down, horsetail (Equisetum arvense) is the worst weed you can get in your garden. If you've got it, just be glad you weren't gardening in prehistoric times. Back then, horsetail grew to 90 feet tall and you were in danger of being stepped on by a brontosaurus while weeding.

The worst thing about horsetail is the speed with which it returns to make your life miserable after you weed it. No matter how great a weeding job you do, it will be back, practically to full size, within a week!

Do what we did at Seattle University. Plant a mix of shrubs, ground covers and fast-growing perennials that are thick and tall enough to hide the horsetail. Shrubs that hide horsetail include Cistus (rockrose) Lonicera pileata (privet honeysuckle) Lonicera nitida (Box honeysuckle) and rosemary. My favorite perennial to hide horsetail is the prolific hardy Geranium oxonianum 'Claridge Druce.' It will seed all over your garden, but new seedlings are easy to remove in spring. These drought-tolerant plants look great in their own right and because they are so thick and tall, no one will see the hoards of horsetail growing within."

Washington Toxics Coalition recommends controlling it by persistently hand-pulling or hoeing the above-ground growth as soon as it appears. This will weaken the plant over time. It does die back over winter, when you could cover the affected area with black plastic (for a duration of 2 years), but even this may not be entirely successful.

An article by Irene Mills in the Fall 2008 issue of the Northwest Perennial Alliance's Perennial Post says that pulling, digging, and covering with black plastic are a waste of time. The author recommends keeping an eye out in April for emerging spore-bearing stalks, and cutting these off and disposing of them in the garbage. She suggests improving the soil texture (improve drainage, add organic matter, increase soil fertility, and in some cases increase soil pH). She recommends this guide called "Controlling Horsetail" from Swanson's Nursery, originally published in Gardens West by Carol Hall.

Date 2019-02-23
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Plant Answer Line Question

Keywords: Weed control, Lawns and turfgrasses, Lawns--Care and maintenance

I am looking for general information on lawn care, lawn renovation, lawn fertilizer and alternatives to pesticides.


Here is information from the web pages of Seattle Public Utilities. An excerpt:

Fertilize Moderately:
Use "Natural Organic" or "Slow-release" fertilizer. These fertilizers release nutrients to feed the lawn slowly, and less is wasted through leaching or runoff into our streams. Look for the words "natural organic" or "slow-release" on the bag.

Fertilize in September and May:
With slow-release or organic fertilizers, you can fertilize just twice a year, in mid to late May and again in early September. If you choose to fertilize only once, the fall application is most important because it helps the grass grow new roots and store nutrients for next year's growth.

How much to apply:
Washington State University (WSU) recommends that home lawns receive 3 to 4 pounds of nitrogen (in a balanced fertilizer) per 1000 square feet of lawn each year. Grasscycling can supply at least one-quarter of that. Split the rest between the May and September applications. Avoid fertilizing in the early spring because it makes lawns grow too fast (unless your lawn needs help recovering from disease or insect damage.) Wait until May.

Mow better:
Grasscycling returns valuable nutrients to the soil every time you mow! Mow high, mow often and leave the clippings to see results.

Fertilize for a healthy colored lawn"
Healthy lawns are a medium green color (top), depending on the variety of grass. The darkest green turf (bottom), which many people strive for, is not in fact the healthiest turf. Overfertilized lawns are more prone to disease, thatch buildup, and drought damage.

Test for calcium deficiency:
Soils west of the Cascades are often low in calcium. Apply lime in the spring or fall if a soil test shows a calcium deficiency or acid soil conditions (pH less than 5). Call WSU Cooperative Extension (206) 296-3900 for information on soil testing and their Home Lawns bulletin."

If you would like to renovate your lawn, this is something you could do in the fall. Local garden writer Ann Lovejoy describes her method in The Handbook of Northwest Gardening (Sasquatch Books, 2003):

  • Mow the existing grass as short as possible.
  • Spread 1 inch of clean crushed quarter-ten gravel (not pea gravel) evenly over the entire surface.
  • Spread 1 inch of compost over the gravel.
  • Top-seed with a regionally appropriate blend if the lawn is thin and spotty.
  • Wait 6-7 weeks before mowing again.

Should you decide to start afresh, here is information from the Washington State University Extension website which discusses grass seed for Western Washington gardens. Here is an excerpt:
What Grass Seed Grows Well in Western Washington?
"To establish a lawn in western Washington, choose a combination of turftype tall fescue grasses and turftype perennial rye grasses. A mix that adds up to about 90% of these two grass seed types will grow well in either sun or light shade in western Washington. Turftype perennial ryegrass takes full sun and stands up to traffic. Turftype tall fescues are adapted to shadier locations. In combination, the mix works for a lawn in average light conditions. Mixes containing fine-leaved fescues or chewings fescues will also establish well. Fine-leaved fescues offer bright green color, and will take some shade, but do not take heavy use.

"Many commonly-grown grass types from other areas of the United States will not thrive in western Washington's cool, dry summer climate. AVOID mixes with high concentrations of Kentucky blue grasses. DO NOT PLANT Zoysia, bermuda, dichondra, centipede, carpetgrass, St. Augustine, or mondograss. Buffalograss isn't suitable for western Washington, though it may thrive in eastern Washington.

Soil Conditions for Planting a New Lawn:
"Establishing a new lawn successfully depends more on the preparation of the ground before planting than on whether the lawn choice is seed or sod. Lawn failures are often caused by poor soil conditions under the roots. Many times soil surface left for planting after new construction is infertile subsoils, with rocks, lumps, and building detritus left in it. The texture may vary from sands and gravels to heavy, poorly drained clay areas. The best soil texture for a lawn is a sandy loam, containing 60%-70% sand and 30%-40% combined silt and clay."

If the soil isn't well-drained, do not try to amend a heavy clay by dumping sand into it. Adding sand doesn't work, nor does adding gypsum. Amend the soil with organic material, which will help in creating better structure. Use compost, manure, aged sawdust, ground bark, or other organic (previously living) materials. Spread 2 inches on top of the ground and work it in thoroughly 6 to 8 inches down. Getting it completely incorporated is important, because spots of organic material in clumps may decompose and cause a low spot in the finished lawn. Rake away clods and remove large rocks and litter.

University of Minnesota Extension's Caring for Shoreland Lawns and Gardens describes best practices for caring for a shoreline lawn and garden, which includes using compost as lawn fertilizer. An excerpt:

  • If possible avoid the use of chemical fertilizers. Native vegetation does not require the application of additional fertilizer. Use caution if applying fertilizers to lawns and adhere to the following guidelines:
    Have your soil tested to determine how much fertilizer is needed and minimize the use of chemical fertilizers; soil test sample bags are available through the county offices of the University of Minnesota Extension Service.
  • Use compost or manure; this is preferable to chemical fertilizer. However, these also have the potential to damage water quality if used in excessive amounts.
  • If chemical fertilizers are used, select slow-release (water insoluble) forms; see recommendations for fertilizing on next page.
  • Water your lawn after fertilizing, but do not allow excess water to run off into surface waters.
  • Sweep up any fertilizer spilled on hard surfaces such as walks and driveways, instead of washing it off.
  • Use extra caution when applying fertilizer near surface waters; do not spread fertilizer within 75 feet of surface waters or wetlands; use a "drop" spreader and not a "cyclone" spreader to minimize the possibility of getting fertilizer directly into the water.
  • Never apply fertilizers to frozen ground.
  • Leave a natural vegetation filter strip of grass, trees, and/or shrubs next to the shoreline; another option would be to construct a berm along the shore.

You may find this general information about compost, from the City of Seattle Public Utilities and the Saving Water Partnership, of interest.

Here are additional links to lawn care methods. The first three are from the Northwest Coalition for Alternatives to Pesticides:

Taking Care of Your Lawn without Using Pesticides.

Dealing with Dandelions.

Pesticide-Free Techniques for Dealing with a Mossy Lawn.

From Toxic-Free Future (formerly Washington Toxics Coalition):
Choosing Fertilizers for the Lawn & Garden.

From Beyond Pesticides:
Read your "Weeds"--A simple Guide to Creating a Healthy Lawn.

Date 2019-05-22
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Plant Answer Line Question

Keywords: Weed control, Rosaceae (Rose Family), Mulching

We recently had a large blue spruce tree cut down and had the stump ground. Would the resulting sawdust be a good mulch for roses?

Also, what is your opinion of using a pre-emergent herbicide for weed control in our rose bed?


Sawdust has high carbon content and may rob soil of nitrogen and moisture. It is also recommended for acid-loving plants and may be problematic for roses. There may also be compaction problems with sawdust, so it may need to be combined with other mulching materials to improve water penetration. Sawdust also decomposes slowly and compacts (Source: Mulch It! by Stu Campbell, Storey Communications Inc., 2001).

You may also be interested in two articles by Linda Chalker-Scott. In Wood chip mulch: Landscape boon or bane, she discusses the pros and cons of wood chip mulch. She also comments on sawdust in an article called The Myth of Pretty Mulch.

If you had spruce chips, they would be fine for mulching roses. Avoid letting mulch touch the main stem; the goal is to pile it on the root system away from the stem. You can remove it in the spring, or at least be sure that it's not too deep. While mulch protects from cold in the winter and drought in the summer, if it's too deep, water cannot get to the root zone of the plant.

I would recommend that you avoid chemicals, as I find that you have to pay more attention when you use them than if you just wander through the garden now and then and pull all the weeds you see.

Pre-emergent weed controls never provide complete weed control. The most important thing to do is weed the area first, as pre-emergents only control weeds that have NOT sprouted. And if you have lots of seeds in the soil, don't expect weed killer to eliminate them all. If water is required, beware of too much water (i.e., rain) that can wash away the herbicide.

Rather than use a chemical, I would weed the area now and then apply mulch. In addition to protecting the roots and soil, the mulch will suppress weeds, possibly until spring. You will have to watch for weeds that do sprout and be sure that you don't let them go to seed. Otherwise, you will set yourself up for lots of future weeding. Chemicals don't really help in situations like that, as you have to time their application perfectly. Hand weeding and mulching--well timed--can work better than any herbicide.

Date 2019-05-16
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Plant Answer Line Question

Keywords: Acanthus mollis, Weed control, Invasive plants

I am wondering how invasive bear's breeches is? I have heard it can be invasive in the Northwest. Will I be battling roots or suckers constantly? Can it take over any plants near it?


Acanthus mollis, or Bear's breeches, is not listed as noxious in King County, Washington State, or on the federal list of noxious plants. This is not the same as saying it isn't potentially aggressive, although I've never heard about it being a serious problem here. It is considered invasive in parts of Australia, though.

The Plants for a Future database offers the following information on this plant and its growing habits:
"Plants can become invasive, spreading by suckers, and they are difficult to eradicate due to their deep roots."

According to the Pacific Northwest site, Rainyside Gardeners, it is sometimes difficult to get this plant to bloom. A Washington State University Extension site says that Acanthus mollis is potentially invasive in climates warmer than ours.
"This species is classified as a groundcover in that any pieces of root cut from the original plant can easily contribute to further plant spread."

If you want to grow it but are concerned about it spreading, you could try containing the roots with an 8-inch root barrier (similar to what is used to keep running bamboo in check). On the other hand, if you have this plant and decide that you wish to be rid of it, the book Wildly Successful Plants: Northern California Gardens by Pam Peirce and David Goldberg (Sasquatch Books, 2004) says that removing every bit of root over two or three seasons of growth should get rid of the plant. If you cannot eradicate it by continually digging up each new shoot, you may have some luck using a flame weeder (with due caution and appropriate protection). Northwest Center for Alternatives to Pesticides describes how to use this tool.

Date 2019-02-22
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Garden Tip

Keywords: Weed control, Organic gardening, Mulching, Herbicides

A common question we get at the Elisabeth C. Miller Library is How do I kill weeds without hand digging but without using toxic chemicals? Further discussion with the gardener reveals he wants to buy a product that he can spray on the weeds, once. Organic gardeners have it easier now compared to a decade ago, with a number of less-toxic weed killers on the market, but the fact is not one of these products is a magic bullet.

  • Corn Gluten Meal (Concern's Weed Prevention Plus and Whitney Farm's Weed Whompin Mulch) is a natural product that prevents seeds from rooting once sprouted. The downside is that it doesn't work during rainy weather. Another consideration is that recent studies show it acts as fertilizer because it is rich in nitrogen, so in garden beds it may actually increase weeds. Its best use would be for weeds in lawns, according to an article in Organic Gardening, Aug/Oct 2008.
  • Potassium salts of fatty acids (Safer Superfast Weed & Grass Killer) kills the tops of all plants, but not the roots. It works best on annual weeds like chick-weed and bitter cress, but would have to be repeated a few times to kill perennial weeds with root reserves, such as dandelion.
  • Pelargonic acid herbicide (Scythe) is another type of fatty acid, similar to soap, that kills weeds by drying out the leaves. As mentioned above this product works best on annual or biennial weeds and must be reapplied a few times to kill perennials.
  • Vinegar from the kitchen doesn't kill weeds, only disfigures them. Commercial products (Burnout, Bradfield's Horticultural 20% Vinegar) work if used in hot weather, but are quite caustic and great caution must be used not to inhale the fumes or spray the skin. Natural, yes, but toxic.
What does it take to get rid of weeds? A multi-pronged approach: physically remove weeds when they are young, reapply mulch every year, shade weeds out with desirable plants, and don't let weeds go to seed.

The Northwest Center for Alternatives to Pesticides publishes excellent articles on non-toxic pest control. Two good articles on weed management are available free online: Managing Weeds in Shrub and Flower Beds and Landscape Weed Control

Date: 2007-04-03
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Garden Tip

Keywords: Rumex crispus, Taraxacum officinale, Weed control

The best time to pull up weeds with long tap-roots, like dandelion and yellow dock, is just after a good soaking rain. Even without a special tool, the tap-root can be wiggled a bit and then tugged right out of the ground. If even a bit of root is left behind it will regrow, but the plant will be weaker and will eventually die if the tops are cut off repeatedly. A good article on controlling dandelions organically is available from Northwest Center for Alternatives to Pesticides.

Date: 2007-03-05
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Garden Tip

Keywords: Weed control

As the garden grows, so do the weeds. Act early before the problem gets totally out of hand. At the very least don't let the weeds go to seed. The book Maria Rodale's Organic Gardening (Rodale, 1998) has a chapter on fighting weeds that includes suggestions for getting motivated. The author suggests focusing weeding efforts on just one defined patch per session for a set amount of time. She also reports the best motivator of all is a deadline: invite your friends and family over for a Sunday afternoon barbeque and be amazed at how much weeding gets done in the morning.

Date: 2007-04-03
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Garden Tip

Keywords: Rubus discolor, Weed control, Organic gardening

Eradicating blackberry vines may seem hopeless, especially if you don't want to use chemicals, but don't give up just yet. The Northwest Center for Alternatives to Pesticides advises gardeners to cut off the top growth, dig out the main root-ball, and then follow-up by mowing all new growth. Planting desirable plants to shade out the sun loving blackberries is also critical. Read the NCAP's blackberry management plan (pdf).

Date: 2007-05-16
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Garden Tip

Keywords: Weed control

Think you'll solve your weed problem by laying down some weed-barrier fabric, bark mulch and a few shrubs planted through a slit? This "permanent" solution may in fact cause more weed problems than it solves. Linda Chalker-Scott, Extension Urban Horticulturist, Puyallup Research and Extension Center, Washington State University did research to debunk this myth. Read about why landscape fabric fails.

Date: 2007-05-16
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Garden Tip

Keywords: Invasive plants--Control, Weed control

Weed fact sheets are available from UC Davis, in cooperation with the Nature Conservancy. This is an excellent resource for learning how to control some of the most tenacious invasive plants in the US. Many weed profiles have color pictures, "success stories," and references to research.

Date: 2007-07-13
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