Sustainable Gardening

Practical answers from nature-loving garden gurus

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Weeds and Weeding

What Are They? Any plant we don't want, at least where it's growing. There are annual, biennial and perennial weeds. Unlike most plants that produce hundreds of seeds per year, ragweed produces 15,000, purslane produces 52,000, and so on. Most are deposited in the soil, so weed populations increase yearly if they aren't managed. See what we're dealing with here?

What's Wrong With them? They compete with the plants we want for water, light, soil nutrients, and space. And by definition, we don't like the way they look.

What's to Like About Them? They stabilize and add organic matter to the soil, while providing habitat and feed for wildlife. See, they're not all bad. Some even look good, like this creeping sedum that blew into my garden.

Prevention — Mulch and Constant Vigilance

• Mulch, 2-3 inches in spring, is the number one prevention technique. You can apply it in the fall but make sure there's still 2-3 inches in the spring.
• Remove as many weeds as possible before applying the mulch.
• Close spacing of plants helps, too. Never forget that bare ground is an invitation to weeds. (If you see bare ground, it won't be bare for long.)
• Viligance is key because things just get worse if you let your weeds throw their seeds around. So keeping on top of weeding is really important in preventing weeds. And if you're just starting to get a handle on them, remember it'll be much easier next year.
• If you're starting a new garden or doing a major renovation of an old one, now's your chance to do the soil preparation work that will save you countless hours of weeding over the next years — maybe decades. Find out the details below.

Weeding

All gardens have them, period. You can hire someone to do the weeding for you or, if you're a gardener, you grab a tool and get some exercise. Besides, it goes pretty fast and makes a huge difference in the appearance of the garden, so it's surprisingly gratifying. (Lots of gardeners actually enjoy weeding, and I admit to being one of them.)

Tools

Hoes are the old-fashioned, back-saving stand-up tool used by farmers and gardeners since forever. Their flat blades slice through shallow roots but often remove just part of the deeper ones, which then grow back. And the chop/draw motion can take lots of strength and still be hard on the back (though at least the extreme bending over of hand-weeding is avoided).

Hand tools are used by most gardeners I know, maybe because they let us get close to the ground where we can get a good luck at our plants. To prevent backaches I stop after 30 minutes of weeding and find something else to do in the garden.

Trowels are, for me, the main tool — okay, trowels and my pruners — especially the pointy one you see in this photo. The point means it's terrific at digging, and it even measures the depth of the hole you've dug — brilliant!

Japanese gardening knives are loved by many gardeners, and I use one occasionally myself. It's a tool that'll never go dull on you.

Cobraheads made a splash recently in the world of gardenbloggers after the company smartly gave away a few and garnered lots of favorable attention. I was happy to get mine (swag!) but honestly, haven't taken to it. It hangs on a peg somewhere.

Weed burners and weed flamers are attached to common butane gas tanks. With the flame held just above each weed, fluids in the weed are boiled, the weed is killed, and it takes less than a second each for medium-size weeds. Annuals like dandelion are killed easily this way; perennials may take two flamings done two weeks apart. Have I used one myself? No, so if you have, let me know what you thought of it.

[This just in: "My husband bought me a weed torch, and it isn't very useful. Some weeds don't fry very easily, and it takes about 5-10 seconds of hitting it with a flame to really damage it.  I can pull/dig much faster than that. But, it sure is fun!  Sometimes it just feel good to watch the really annoying ones shrivel and die.  So I highly recommend it for entertainment, but not necessarily effective weeding. Lisa Pflug at www.countrysideroses.com" Thanks, Lisa.]

Organic Herbicides

You know how this works. Sustainable gardeners, like practitioners of Integrated Pest Management, use the least toxic tactic first, which is why I listed tools first. (And who among us couldn't use the exercise?) But sometimes other tactics are called for.

Vinegar, the concentrated 10 percent solution (more concentrated than cooking vinegar) has many fans as a spray-on weed-killer. My local hardware store carries large quantities of the concentrate, which gardeners share among themselves.

Corn gluten powder is generally effective as a pre-emergent weedkiller in early spring, and organic gardeners commonly use it on their lawns. (Or they may just tolerate weeds, or use their weeding tools.)

Commercial organic herbicides are not as fast-acting or as lethal as synthetic herbicides and it may take several applications to do the job.

• Weed-A-Tak is made of clove, wintergreen, peppermint and other oils. Jeff Gillman tells me that the most effective oil IS clove oil but that it's also the most dangerous — even to humans. Wouldn't you know?
• Burnout is made of lemon and vingear
• Concern Fast-Acting Weed Killer is made of soap and ammonia. If you've tried it, let me know.

For more about organic herbicides see "The Truth about Organic Fertilizers and Weed Control" here on this site, or go directly to Jeff Gillman's The Truth about Organic Gardening.

Synthetic Herbicides

Now these are products I discourage the use of except when it's absolutely needed and only under the right conditions (e.g., no wind) and sparingly.

Roundup is the most commonly used synthetic herbicide, with the active ingredient being glyphosate. Read my article "When good People Use Roundup" about the controversy over its use, including the rare situations in which it may actually be the best choice.

Herbicides for Lawn — The Washington Post's environmentally savvy Joel Lerner recommends the following synthetic lawn herbicides "if absolutely necessary": Team, Gallery and 2,4-D. Like Roundup, they may have their place and really be necessary sometimes, but my reaction is: Who says lawns have to be perfect and weed-free?

Landscape Fabric

The purpose of landscape fabric spread across the soil is to block weed germination while allowing air and water to penetrate, but I still hear complaints that not much air or water can penetrate it. It can also look pretty awful — more like black plastic than the nicer-sounding "fabric." Third, plant roots often get entangled in the fabric, making it hard to transplant them. And finally, landscape fabrics don't prevent the tougher, perennial weeds from emerging. But then I've never tried the stuff. If you have, let me know how it worked out.

Dealing with Weeds when Preparing New Beds

When preparing new beds or doing major renovations of old ones, there are two tactics you can take regarding weeds: kill them and all their seeds first, or go ahead and plant in that spot but do a lot of weeding in the first year. The latter is the tactic I've always taken and recommend for my low-maintenance clients, especially if they don't want to wait a whole year or more for the kill-all-the-weeds method to work. So yes, there will probably be lots of weeds in the first year but after that, not nearly as many, especially if you weed regularly and use enough mulch.

How to Pre-Kill Weeds in the Garden

• Twelve to 18 months ahead of time remove all plants (sod and weeds) from the new garden or if it's a renovation, remove and set aside the plants you're keeping. Don't forget to remove their roots, too. Next, how to kill those seeds?
  • Shade, created by black plastic that's weighted down along its edges, takes at least 10 months.
  • Solarizing needs plenty of hot days to work. After mowing and watering the area, cover it with .5 to 4-mil clear plastic and pull it tight and seal its edges to retain the heat. Heat can destroy beneficial underground life, though they'll recolonize quickly when the garden is functioning again. It takes at least 8 weeks to do the job.
• Rather than digging up all the sods and weeds beforehand, a popular slow-gardening technique is the lasagna method. Six to 20 sheets of newspaper or several layers of cardboard are spread over the area, plants and all, wet thoroughly, then covered with 3-6 inches of organic matter (compost or leafmold mulch. ) After a year it'll all decompose, leaving greatly improved soil in its wake.

Preparing Beds without Pre-Killing Weed Seeds

• Spadework is the technique I use, in which I slice under the sod or weeds and shake off the excess soil before throwing it all on the compost pile. Sod that's removed can alternatively be used to fill in holes in your lawn.
• Tilling is controversial these days, with many experts and regular gardeners complaining that it pulverizes the soil and destroys so many of its beneficial microorganisms. If you DO rent a rototiller, it's recommended that you use it when the soil is neither wet nor totally dry, and do only one pass with it.

Good Information on Line

• NC State's huge compilation of weed links.
• Penn State's Landscape Problem Solver
• Va Tech Weed Identifier and the Rutgers Weed Identifier and the U. of California's Weed Identifier.
• There's a whole video about weeds and weeding by Washington Gardener Magazine's Kathy Jentz coming soon on MonkeySee.com.

Stories from Garden Blogs

• Here I lament the public's lack of love for weeding and propose a new attitude toward weeds altogether.
• Don't miss Amy Stewart's Battle of the Weed Killers — her test between vinegar and Nature's Avenger, which contains orange oil, with great reader comments.