I remember how surprised I was back in the 80s when I learned
in plant physiology class that all the common herbicides and
"weed-and-feeds" - yeah, the ordinary kind that you buy off the shelf
at Home Depot - contain the same ingredients as Agent Orange. They still do. Oh, and of course there's Roundup, the #1 used chemical herbicide in the world, now widely believed to cause non-Hodgkins lymphoma.
But there are plenty of tools in the organic weed control toolbox. Any one of them used alone works okay, but if you use a few of them in combination, it is pretty easy to keep weeds under control. Like much of what happens in the vegetable garden, diversity is a key to success.
ORGANIC WEED CONTROL TOOL #1:
Double-dug raised beds.
How you prepare your soil in the spring has a big effect on how easy it will be to weed your garden during the summer. Weeds are fairly easy to deal with in my garden, because the soil is so loose and friable down deep that weeds just pull right out by the roots, very easily. It really is my number one organic weed control method.
Double digging also allows me to grow my plants much closer together than is traditional, and the tight plant spacing provides a “living mulch”, which helps suppress weed seed germination. If you want to learn about the double-digging method, click here and scroll down to watch the video.
ORGANIC WEED CONTROL TOOL #2:
Degradable organic mulch.
A thick covering of mulch is great at preventing weed seed
germination and growth (as well as conserving water and nutrients). If we were
talking about perennial flowerbeds, where the soil does not need to be worked
annually, you could just spread a nice deep layer of bark or wood chips and
call it good. But mulching is a bit trickier in the vegetable garden.
Because vegetable garden beds get worked every year during planting, when incorporating compost, and at harvest, you need a mulch that will break down on the surface fairly quickly, and is either easy to remove, or that won’t harm the soil if dug down in.
Wood or bark chips are not recommended for several reasons. They are coarse and make deep soil cultivation difficult. But the real problem with them in the vegetable garden is that you never want to incorporate any dry, high-carbon material down deep into the soil. When high-carbon materials get decomposed by fungus, the organisms take the nitrogen they need for the breakdown process from the soil (and your plants). So we have to cross woody mulches off the organic weed control list.
What can you use to mulch around vegetables? My favorites are dried fall leaves, weed-free straw, uprooted weeds, grass clippings, thick newspaper layers, or even cardboard. None of these is perfect. The perfect mulch would be compost, but no matter how much I make I never have enough to lay down a thick enough layer to be an effective mulch, so I don't list it. But if cost is not a big concern, go out and buy as much compost as you need to cover your vegetable bed a couple of inches deep in compost, and forget the rest of this list! Your vegetables and soil critters will be in heaven, it will suppress germination all summer, and you can just fork it in next spring.
Why these are my favorite mulch choices:
Fall Leaves are plentiful in my neighborhood, and I don't even have to rake them! My neighbors do the work for me, and just bring over bag after bag of lovely ash, oak, maple, linden, cottonwood, and apple leaves. We unbag them into a huge pile up against the south side of the house under a plum tree, where they suppress weeds. We use them the rest of the year to mix with the high-nitrogen stuff (manure, kitchen scraps, coffee grounds) in the compost, to mulch our flowerbeds and the vegetable garden, and to give back to our neighbors when they decide they want to use some to mulch their own gardens.
Alfalfa hay adds a bit of nitrogen to the soil, and comes off a bale in compressed flakes that are thick enough to stay in place and really suppress weeds (a good thing because it usually contains weed seeds). Alfalfa hay protects garden soil for the winter, is easy to rake off in the spring, and is great in the compost. Once you decide to use this method, though, commit to stick with it. Alfalfa will bring weed seeds in, so once in awhile you'll need to toss another flake down here or there to smother them if they pop up. (If you can find it - it's now out of print - read The No-Work Garden Book by Ruth Stout. She never dug or did anything to the soil but keep it buried in alfalfa mulch. The worms did all her soil work for her, and if a weed popped up, she just tossed another flake of hay on it!)
Straw is also an excellent mulch material. It is similar to alfalfa in its qualities and habits, but it is much lower in nitrogen. It also comes off a bale in flakes, but they don't hold together as tightly as alfalfa and are not as impenetrable to weeds. And it doesn't smell as wonderful as a fresh bale of alfalfa does! You can buy weed-free straw (or alfalfa), but bear in mind that it has probably been sprayed with herbicides, and even though it doesn't contain weed seeds, it will contain tons of grain seeds, which will sprout. If you use straw, 1) put it down really thick so that it suppresses the growth of it's own seeds, and 2) when some sprout, squeeze thick bunches of the sprouted straw mulch between both hands and pull up a bunch at once. Then just invert the mass, roots up. You can weed a whole bed this way pretty fast.
Uprooted weeds are put to good use in our garden because we have a lot of succulent purslane where I live. I tend to let it grow until it looks like it’s starting to compete with my crop plants, and then just pull it up and invert it around the base of the vegetables. Because I double-dig my vegetable beds, weeds pull out very easily, especially after morning watering, and I like to let the weeds help me by first becoming mulch, and later compost.
Grass clippings (herbicide-free only) work great if you have enough of them. Over time they will tend to dry up and blow away. Just keep mowing and applying.
Newspaper works pretty well provided you lay it down thickly enough. 6-18 sheets of newspaper, believe it or not, can actually stop most weeds from coming through. Newspaper can be a bit challenging to work with though - getting it all thick enough and even around the base of every plant in your garden. It might even be more work than weeding by hand. And colored newspaper, even the non-shiny kind, has colored inks that can contain heavy-metals, which I’d rather not have decomposing in my soil. (I sure miss the old colorless Wall Street Journal - it was the perfect mulch!)
Cardboard is easy to come by and works pretty well. But it has little channels in it where earwigs like to hide in the day, so they can sneak out and eat my collards and marigolds at night.
All these negatives aside, mulching with one or a combination of these is better for the soil than leaving the surface barren, where weeds will take over and compost near the surface will get baked away.
ORGANIC WEED CONTROL TOOL #3:
Root slicer: the nijiri kama.
I cannot tell you how much I love this tool! I’ve tried every hoe there is, and none of them compare to my little Japanese weeding sickle, or nigiri kama, the best weeding tool I have ever used. The Japanese are masters of hardened tool steel - this puppy is sharp and has stayed sharp through two seasons. I just pull it toward me about a quarter-inch below soil level and it slices off weed roots cleanly. It’s easiest to use when the soil is slightly moist, not bone dry, and this is true for all hand-weeding techniques.
Don't try to weed a dry garden. I keep the nijiri kama by the back door, and every day I go weed for a few minutes. It’s a meditation for me - I go hang with my vegetables, the butterflies, the latest little zucchini. This tool has made me love my few minutes weeding every day. Really.
I know that some people aren't going to like the idea of hand weeding being part of the organic weed control toolbox, but seriously, if your soil is moist (not soggy) and it's a beautiful evening, just allow yourself to "get in the zone" with your garden for a few minutes. It helps me slow down, re-center, and connect in with myself and the earth. Try weeding with the nijiri kama, and you'll become a Zen Weeder!
(Addendum Summer 2013: the "collinear hoe" from Lee Valley Tools or Johnny's Selected Seeds works almost as well - though nowhere near as sharp - while standing without bending.)
ORGANIC WEED CONTROL TOOL #4:
Uprooter: the hori hori.This tool is shaped like a big knife. It isn’t really sharp like the nijiri kama, just wicked strong! You absolutely cannot bend it (dare ya’!). You could dig dandelions out of baked clay with this thing, as well as plant, weed, cultivate, and harvest. I used mine every day of the three years that I was the landscaper at Naropa University, and except for wearing away the black finish, it’s like new. Mine is the hardened steel version, but I’ve heard the stainless steel version is lighter, just as strong, and has a better handle. (Maybe I’ll ask Santa for one this Christmas!) And the Japanese don't have a problem calling a spade a spade: "hori hori" means "diggy diggy" in Japanese. Love it!
ORGANIC WEED CONTROL TOOL #5:
You can make a homemade spray from vinegar and salt to kill weeds. This is a popular "organic herbicide" that you'll find all over the internet (especially Pinterest). It works, but I’d rather save salt and vinegar for potato chips. One problem is that this will only kill the top of the plant, not the root. It will work well on little baby weeds, but big mamas with established tap roots will just grow back.
Another problem is that salt is toxic to soil organisms and above a certain concentration prevents other soil mineral nutrients from being taken up by plants. Once in the soil, it does not go away, and if you spray very much of it, or for more than one season, you could end up with a serious problem. This mix is great if you have weeds coming up through the cracks in your driveway, but I wouldn't recommend it in the vegetable garden. (See the next Tool for a better alternative).
That said, here is the recipe if you want to try it: ½ lb. salt, ½ gallon distilled white vinegar, ½ teaspoon dishsoap. Mix and spray only on the weeds, and on a windless morning so that overspray does not kill your crop plants. Also note
Just because this is a natural product, do not think it is benign. Salt is very toxic in the soil, and can even damage concrete. Use sparingly.
ORGANIC WEED CONTROL TOOL #6:
Much better than the homemade stuff, WeedPharm is a concentrated, food-grade vinegar product (no salt), which works by damaging the wax on the surface of plant leaves, causing them to dry out. WeedPharm is 20% acetic acid, whereas household distilled vinegar is only 5%. WeedPharm works great, but again, only on the top of the plant. But it will kill weeds if you catch them when they're little enough.
Make an overspray preventer by cutting a hole in the
end of a large coffee cup, stick the spray nozzle through the hole, and
you’ll have a little “conehead” that will prevent overspray from killing surrounding plants. This will not damage the soil like salt preparations will, and is certified for use in organic agriculture. Available at Whole Foods and better garden centers.
Safer Brand Fast Acting Weed and Grass Killer is another option. It is a “potassium salt of fatty acids”, which also damages the cuticle of the leaf. Same as with homemade sprays - be extremely careful not to let overspray hit your vegetable plants.
ORGANIC WEED CONTROL TOOL #7:
If you wish to reclaim a badly overgrown weed patch for use as a garden next year, you can mow and rake it, water it very deeply, wait a few days for seeds to start germinating, and then cover it tightly with clear plastic for six weeks. Put bricks around the edge or bury the edge with a bit of soil to keep the plastic tight. The heat buildup inside will kill germinating seeds. To really do a job, you can uncover it, cultivate it again with a level rake to stir up unsprouted seeds, then water and do the same thing with the plastic again for another six weeks. Next year you’ll have a nice, weed-free patch of ground for a new vegetable garden.
ORGANIC WEED CONTROL TOOL #8:
Corn gluten meal.
If you want a non-toxic product to use in early spring (and it only works in early spring) before weed seeds even sprout, you can use corn gluten meal as a "pre-emergent herbicide". What that means is that it will prevent weed seeds (and vegetable seeds, I might add) from growing, by inhibiting their root growth. Lay it down as soon as the soil is workable, but well before last spring frost. It's good for lawns, but you have to use a lot - 20 pounds/1000 sq. ft. - which can get expensive. If you've timed it right (just as weed seeds are getting ready to sprout) it will kill emerging weed seedlings, but will have decomposed by the time you get ready to plant out your vegetable seeds. It also provides nitrogen, a good thing! It will have no effect on established plants, weed or otherwise.
The combination that works for me is double-digging my beds with lots of compost, which makes weeding by hand very easy. I mulch with fall leaves, grass clippings and freshly-pulled weeds, which next spring will go into the compost bin. I don’t use any sprays, because in my case stooping to spray is no easier than stooping to pull, and I can do without the added salt.
If I haven't been diligent and there are a lot of little guys sprouting up, I use my nijiri kama or collinear hoe. It's very fast, especially if you just leave the weeds on the surface as mulch. They turn brown pretty soon, and green crops look beautiful sticking up vibrantly above them.
If you have any favorite tools in your organic weed control toolbox that are not listed here, in invite you to share them here using the form below. You'll get your own page on this website!
Do you have a raised bed or trellis idea to share? Bragging rights to a monster pumpkin, or a mistake you made that you can only laugh about in hindsight? Share it here by creating your own personal page on this site, which your family, friends and others can see and comment on. Jump on in and get your hands dirty. We know your thumbs are green!