Bleach as a Weed Killer

In an effort to keep chemicals out of the garden (for the sake of pollinating insects, the soil, our water, and our personal health), I've tried many organic means of keeping weeds at bay. Generally, if I stay on top of hand weeding, there's really no problem. (For examples of other organic weed control techniques, see these posts: The Organic, Weed Free Garden; Lazy Ways to Weed the Garden; The World's Easiest, Safest, and Best DIY Weed Killers, and Why Newspapers and Cardboard are Better Than Landscaping Fabric.)

But a couple of years back, I had my husband remove a portion of our front lawn to make more room for vegetables and fruits. The grass stayed out of this growing area...until this spring, when it came back with a vengeance. I find the grass is impossible to pull out by hand; the roots stay stubbornly in the soil. So what to do? My usual organic weed killers just weren't cutting it. So I decided to try something new: Bleach.

The results? Great! By the next day, some very stubborn weeds were dead, as was the grass. And the invasion blackberry vines that are tough to kill even with Round Up? They were dead, too!

A Few Facts about Bleach

* The chemicals in modern bleach have been in use since the 18th century.

* If you have city water, it contains bleach.

* The ingredients in bleach are organic. However, these natural chemicals are definitely processed. (Read more about that process here.)

* According to OSHA (the Occupational Safety and Health Administration) (which, in my opinion, is extremely cautious), those who use bleach in the workplace must wear a mask and gloves.

* Some people are concerned about bleach and health risks - but most concerns have to do with indoor air quality.

* Bleach kills bacteria, fungus, and molds, and is sometimes used to kill soil diseases. It's also used to kill certain pests (like nematodes). I cannot find proof that bleach kills beneficial microbes in the soil, but I think it's likely. However, you're only spraying the surface of the soil, and bleach dissipates pretty quickly.

Overall, I think that if you can't kill certain weeds by organic methods, bleach is a good option - and far safer than Round Up.

Blackberry vines killed by bleach.

How to Use Bleach as a Weed Killer

1. Choose a sunny, relatively wind-free day. I recommend spraying on the morning of a day that will be hot.

2. Mow, weed whack, or cut back long or tall weeds. This is an important step because a) you'll use less bleach if the plants are smaller and b) the bleach is more likely to kill the plant if you spay near the roots.

3. Rake away what you've mowed or cut off. This ensures the bleach ends up on the part of the plant with roots in the soil, not just on the part of the plant you've cut off.

4. Pour household bleach into a hand held spray bottle. (You could also use one of these.) Use a fresh bottle of bleach, since bleach that's been sitting around quickly dissipates and becomes ineffective. Wear old clothes, just in case you get bleach on them. Wear gloves and a mask, if you like. (I didn't.)

5. Spray the weeds, covering as much of the leaves as possible with the bleach.

6. Remember: Bleach will kill desirable plants, too. If you accidentally spray something you didn't meant to, just clean off the affected area with water. The plant should be fine.

7. Wait at least a day before walking in the area. By then, the weeds should be browning, if not completely dead. Weeds that are in the shade will take longer to die.

8. Wait a week (I think a couple of days would be fine, but let's be extra cautious) before planting anything in the area that's been sprayed. Because bleach may kill some microbes in the soil, I recommend adding compost to the soil before planting, to replenish any soil microbes that might have died.

1 comment

  1. Bleach is also known as sodium hypochlorite NaClO and is not organic because it is not carbon based. It works well at killing everything because it is incredibly corrosive at a 12.6 out of 14 on the pH scale when concentrated in a 10-15% solution (pH of 11 when only 5% bleach is used in solution). Water has a pH of 7 and each digit above 7 increases alkalinity by a factor of 10, so bleach is over 100,000 times more basic than water in concentration (10,000 times as alkaline as water when in 5% bleach solution). In other words, bleach is very corrosive.

    Sodium hypochlorite breaks down into oxygen and sodium chloride (table salt). If you use too much you can add a lot of salt to your soil but in small amounts might be fine if you water the area a couple days after use.