Tackle Weeds the Natural Way

Instead of dousing your yard with chemicals to wipe out weeds, let time and nature work their magic via smothering and solarization

Houzz Contributor. I am a landscape/garden designer, garden coach, writer, and public speaker with over 25 years of professional experience creating beautiful outdoor environments that are lifestyle friendly and Colorado "green". Please contact me at jhcstudios@yahoo.com if you would like more information about my services.

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The last warm weeks of summer and the early days of fall are perfect times to get a jump start on weed and pest control for next spring’s gardens. Smothering and solarization are two methods you can use to prepare garden spaces — both large and small — when time is not a factor. Both methods use simple, inexpensive and chemical-free techniques that result in healthy and nutrient-rich soil for planting.

by Jocelyn H. Chilvers »

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Smothering is simply an exaggerated form of mulching. A thick layer of paper or cardboard, topped by several inches of organic matter, deprives existing weedy plants of light, thus inhibiting their growth. By using organic materials that decompose quickly, you also get the benefit of composting. Plant directly into the smothered area once the existing weeds are conquered.

How to smother weeds:

Mow or chop the existing vegetation in the area selected for future planting.
Spread a layer of newspaper (exclude colored pages), newsprint or brown kraft paper (eight to 12 sheets thick), or three to four layers of cardboard. Be sure to overlap paper edges so there are no gaps.
Saturate with water.
Cover the entire paper area with a 4-inch-layer of organic material — shredded wood fiber, wood chips, pine needles, cocoa hulls, etc. Alternatively, an 8-inch-layer of lighter materials, such as dried leaves, grass clippings, or weed-free straw, may be used.
Let the area rest through the fall and winter.

This technique works for areas both large and small, in the sun or in the shade. It’s not a cure for noxious, perennial weeds that have aggressive root systems, but it’s fairly successful way to eliminate annual and biennial weeds as well as many grasses.

by research.pomona.edu »

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Solarization uses radiation from the sun plus moisture to heat soil to 99 to 125 degrees Fahrenheit. This treatment not only kills weeds and weed seeds, but also soilborne pathogens such as fungi, parasitic nematodes, insects and some bacteria. Soil solarization also speeds up the breakdown of organic matter in the soil, resulting in more available nitrogen, calcium, magnesium and potassium. It’s a simple, chemical-free way to revitalize an old planting bed or prepare a new one.

How to solarize weeds:

Rototill or spade existing plant material and additional organic matter (chicken manure, grass clippings, etc.) into the soil. Decomposing organic matter contributes additional heat to the process and can also protect soil microbes.
Rake the soil smooth and lump free — the goal is a clean, flat surface.
Wet the soil to a depth of 12 inches (the moisture is critical to conduct heat through the soil). Keep the soil moist throughout the solarization period.

by Jocelyn H. Chilvers »

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Cover the soil surface with clear (preferably UV-stabilized) plastic, 1.5 to 3 millimeters thick. The plastic must be held tightly against the soil surface; secure the edges by burying them 5 to 6 inches into the soil.

Note: Thinner plastic is less expensive and may be used in a double layer, but is more prone to wind or animal damage. In cooler climates, using black plastic for a longer period of time may be as effective as clear plastic.

Four to six weeks of solarization during the long, hot days of summer are enough to kill most weed seeds and soil pests. In the cooler days of fall and spring, six to eight weeks may be necessary.

by Jean Marsh Design »

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Solarization is especially effective for controlling annual weeds and pests in gardens with plenty of sun and available moisture. It can be used in raised gardens as well as areas slated for new lawns. More detailed research information and technical data on solarization can be found here and here .

More:
5 Ways to Naturally Win the Weed War
5 Weed-Smothering Ground Covers

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Comments

zhogfan Corn gluten meal, a cattle feed, provides weed control plus 10% nitrogen

9 months ago · Like ·

zhogfan If you have Feed,farm store close by cottonseed meal and soybean meal make great fertilizers

9 months ago · Like

nicekato42 Hi Jocelyn,

Thank you so much for such an informative article! I love the idea of smothering the weeds while mulching at the same time. I am in the process of building a house near san jose, california and had a couple of questions for you.

Here are the conditions:
Zone: 10a (I think)
Soil: Dry clay soil
Weeds (or POOP as I saw in your other article): Tall, grassy weeds
Lot size: 1.5 acres

After the house and driveway are done, we'll probably have closer to 3/4 acres left that will need bulk weed control. There will be some trees planted, but we are trying to keep this pretty low maintenance

My current plan was to plant wildflowers here after construction is done, but I've never done so. I'm definitely open to other suggestions for plants, as long as Lavender isn't one of them (my wife hates the fragrance).

Based on your article here, my plan is now to:
1. Smother the weeds with bulk newspaper and natural wood chips (uncolored) (fall - winter)
2. This is the step I'm not sure of - do I need to condition the soil or bring in fertilizer or dirt? (spring)
3. User a bulk wildflower seed mix and evenly spread out (spring)
4. Occasionally water (not sure how often) (spring - summer)

Any and all advice would be greatly appreciated!

Cheers,
David

9 months ago · Like

Jocelyn H. Chilvers David, you may want to add some alfalfa meal in the spring to bring up the nitrogen content in your mulched beds. Your local county extension service can give you good information relevant to your specific location. Check with the wildflower seed supplier, too. A good seed company will have very specific recommendations for preparing for (and establishing) your new planting.
Good luck!

9 months ago · Like

zhogfan If you can get corn gluten meal it is 10% nitrogen where as alfalfa meal is 2.5% nitrogen, and corn gluten will give weed control.

9 months ago · Like

Elena Vega Thank you so much for this! I'm always concerned about chemicals (in food, soils, cleaning products etc.), so this was really helpful — not to mention very well written!

9 months ago · Like ·

Jocelyn H. Chilvers Zhogfan, you are correct in the need to compare labels and understand the amount of available nitrogen in various products. It's also important to do a cost analysis; locally produced products available in bulk could be more economical.
However, corn gluten meal (a byproduct of the cattle feed manufacturing process) would be a disastrous choice in a situation like David's (nicekato42), where he is wanting to plant wildflowers by seed. Corn gluten provides weed control by preventing seed germination — it is a (natural) pre-emergent herbicide.
I'll be writing more about corn gluten in the next installment of my weed control series which will focus on chemicals, both natural and synthetic.

9 months ago · Like

Dolores Stewart Thank you so much all for this ver informative info.

9 months ago · Like ·

Trio Landscaping smothering works great on most weeds, however things that have an aggressive root rhizomes such as quack grass, a problem here in MN, will just lay dormant until they have exposure to grow and can grow as deep as 18" down. Know your weeds your working with so you can have the right expectations. I love suggesting Newspaper and cardboard to clients as I find it much more successful than fabric.

9 months ago · Like ·

cacharlesworth Thanks for the reinforcing solarization advice, a version of which I made up in June to kill the grass on the street side of my sidewalk, so that by planting ivy I can avoid mowing. I bought at Lowe's one $10 "contractor's-size" box of black trash bags and fixed them in place, overlapping (with the direction of the wind), with rocks. Lots of rocks. It worked great in 6-8 weeks. The quick and dirty method! -- yet no quicker or dirtier (but took awhile on my knees getting those bags well fixed in place).

9 months ago · Like ·

valerievalk will this method work on bamboo? zone 7

9 months ago · Like

Jocelyn H. Chilvers valerievalk, my guess is that the root system of bamboo is too aggressive to be controlled with either of these methods. Perhaps another reader has tried it?

9 months ago · Like

5katya5 Do you have any non chemical tips for dealing with thistle removal? It is an aggressive weed in our foothills mountain neighborhood southwest of Fort Collins, CO. Each year I vow to pull each plant removing the roots, but it is so difficult to keep up with. Our property is steep with most of the this on one terrace level. To make things even more interesting, there are rattlesnakes in our area. I've never seen one in our yard, but try to be very vigilant and only garden when my partner is at home, just in case.

3 months ago · Like

Jocelyn H. Chilvers 5katya5, I admire your determination to keep this truly noxious weed under control, even in such difficult conditions! Two ideas for non-chemical control that you could consider are: goats and flame (via a gas torch). There may be someone in the community that has a goat weed service for rent or loan. You may be able to hire someone experienced in using a torch for agricultural field servicing (often along ditches or fence lines where it's difficult to mow), or you could purchase your own. Both of these methods kill the weed tops only, and will have to be done on an ongoing basis. Contact the CSU Cooperative Extension Service in Larimer County for more information/options.

3 months ago · Like ·