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How to Kill Weeds: 6 Ways to Get Rid of Them

Eugene is an avid gardener and has been passionate about growing things for over 40 years.

How to Kill Weeds

Weeds are unsightly and spoil neatly tended flower beds and borders, yards and driveways. Fortunately there are lots of ways to deal with them, either with chemicals or in a natural, environmentally-friendly way, by mechanical means or with household chemical chemicals.

If you have any questions, just leave a comment at the end of this "how to" guide. Also if you find this article useful, please share a link to it on Facebook or other social media using the easy share buttons.

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5-ways-to-kill-weeds-in-your-garden

What is a Weed?

"A weed is an undesired plant, growing in the wrong place".

Yep, that's basically it! There aren't special plants called "weeds" that evolved just to spoil our gardens! Weed isn't a botanical term like annual or perennial or evergreen that describes a particular type of plant. The concept of a weed is subjective and generally it applies to wild flowers, often with ugly foliage or insignificant flowers that spread happily through our flower beds and on our driveways.

They could also be cultivated flowers that we sowed enthusiastically but have now self-seeded in abundance or propagated by other means, spreading everywhere we don't want them to.

Identifying Common Garden Weeds

See my weed identifier guide for information on common weed names:
A Guide to Names of Weeds (With Pictures)

5-ways-to-kill-weeds-in-your-garden

How Do I Kill Weeds in my Garden?

  1. Use a hoe.
  2. Smother them with bark mulch or chipped branches.
  3. Burn them with household chemicals.
  4. Burn them with a blow torch.
  5. Kill them with a systemic weedkiller.
  6. Smother them with plastic or carpet.

Method 1. Use a Hoe

A hoe is excellent for slicing through the stems of weeds. However, if weed growth is extensive on a gravel driveway or in flower beds, the hoed vegetation can be unsightly and may need to be raked up. It's best to hoe in very dry weather so that vegetation dries up rapidly. If you hoe in wet weather and leave weeds lying on the surface of soil, they may take root again if the plants and roots are intact.
A hoe should be kept razor sharp. You can sharpen the blade with a sharpening stone or angle grinder. See link: Sharpening a spade with an angle grinder

The dandelion is one of the most common and recognisable garden weeds.

The dandelion is one of the most common and recognisable garden weeds.

Garden hoe.

Garden hoe.

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Lots of weeds to hoe!

Lots of weeds to hoe!

Sharpening a hoe using a stone or alternatively an angle grinder.

Sharpening a hoe using a stone or alternatively an angle grinder.

Method 2. Use Bark Mulch or Chipped Branches

Mulch is material applied to the surface of soil which helps to suppress weeds and retain moisture. This could be grass clippings from the lawn, bark mulch etc. You can buy bark mulch or make your own chippings from branches using an electric chipper. (See link http://eugbug.hubpages.com/video/Recycle-Garden-Waste-With-a-Shredder ) These normally cost less than $200.

  • Mulch can be used around the trunks of trees to prevent grass growth and the need for string trimming.
  • It can also be applied to flower beds to suppress weed growth.
  • Bark mulch or chippings can be used to create natural pathways in the garden as well.
Electric garden chipper.

Electric garden chipper.

Chipped branches produced by an electric chipper.

Chipped branches produced by an electric chipper.

Method 3. Burn Them With Household Chemicals

Bleach, vinegar and salt will all burn the top growth of weeds and stunt their growth. This is quite effective at killing young seedlings. Established weeds with lots of top growth will grow back, but if they are continually deprived of their leaves, any energy stored in the root will eventually run out and without leaves to produce more energy, they will die. However you need to be persistent.

You can experiment with concentrations, but initially try mixing vinegar with equal quantities of water.

  • Mix 1 part bleach with 10 parts water.
  • If using salt, mix 1 part salt with 10 parts water and add about 2 tablespoon of washing up liquid per gallon to make the solution stick to the leaves.

Make sure you spray in dry weather, and if using bleach, protect your eyes with goggles.

These daisies and dandelions were treated with vinegar. We'll see how effective it is at weed killing  in the coming days!

These daisies and dandelions were treated with vinegar. We'll see how effective it is at weed killing in the coming days!

After a few hours in bright sunshine, the daisies have become scorched. The dandelions are holding out, though.

After a few hours in bright sunshine, the daisies have become scorched. The dandelions are holding out, though.

After 5 days, the daisies are beginning to re-sprout and will need re-treatment. The dandelions will also need to be re-sprayed.

After 5 days, the daisies are beginning to re-sprout and will need re-treatment. The dandelions will also need to be re-sprayed.

Method 4. Use a Blow Torch

A propane / butane blowtorch such as the ones used for torching bituminous felt onto roofs is ideal for burning the top growth of weeds.

  • You don't actually have to incinerate the weeds, just scorch them and they will die after a couple of days.
  • As is the case with using bleach or salt, the results are variable and weeds may grow back.
  • Deep rooted rooted perennial weeds such as dandelions will definitely re-grow. Burning is effective against young seedlings.
  • Be careful in dry weather to avoid dry grass and conifers. You don't want to be responsible for starting a bush fire!
A butane/propane blowtorch used to burn the foliage of weeds.

A butane/propane blowtorch used to burn the foliage of weeds.

Burning weeds with a butane/propane blow torch.

Burning weeds with a butane/propane blow torch.

Method 5. Use a Systemic Herbicide

Glyphosate is a broad spectrum herbicide (weedkiller) which is very effective against annual and perennial weed and grasses. Systemic means that the weed killer is absorbed through the leaves and over a period of 1 to two weeks works its way down down through the plant into the roots.

Glyphosate is well known under the Monsanto brand name "Roundup." However since the patent expired in 2000, it is available from other manufacturers at lower cost.
The herbicide is of low toxicity ( at least that is what current evidence suggests). It is supplied in varying strength formulations and the 360 g/l product is diluted at a rate of 2.5 % concentrate by volume with water. This is equivalent to 25 ml per liter (litre) or 3.2 U.S. fluid ounces per U.S. gallon. Consult the instructions supplied with your product for recommended dilution rates.

A knapsack sprayer can be used or a smaller 1 gallon or 5 liter sprayer. You can also use spray bottles such as the ones window or shower cleaner comes in, for spot treating weeds. Make sure they are washed out first and write on the bottle what it contains, so that weedkiller doesn't end up on your windows or in your shower!

You can also buy ready made instant spray bottles which saves you having to mix concentrate with water, but these are uneconomical as you are just paying for water.

What is the Best Time of the Year and Suitable Weather Conditions to Use Weed Killer?

  • Don't spray on windy days to avoid drift onto lawns or flowers and resulting "collateral" damage!
  • Keep the spray head close to the ground when spraying edges of lawns and around flower beds or shrubs. This makes the spray circle smaller so that there is less chance of getting weed killer on your prized plants.
  • 6 hours is required for spray to dry, and ideally 24 hours for absorption to occur before rain.
  • Anecdotally it's supposed to be a good idea to add a few squirts of washing up liquid to the mix which helps it to stick better if there's light rain.
  • It's best to spray weeds when they have lots of top growth and actively growing to maximize the amount of herbicide absorbed.
  • Don't spray in very dry weather or when there is a drought as plants will have reduced their metabolism and weed killer won't spread through the plant.

Spray weeds before they get a change to develop flowers and re-scatter seed. Weed killer won't kill un-germinated weed seeds on the ground and you will end up having to re-treat once they germinate.

5 liter sprayer for weed killer.

5 liter sprayer for weed killer.

You can use shower/window cleaner spray bottles for spot treating. Make sure to wash them out properly first.

You can use shower/window cleaner spray bottles for spot treating. Make sure to wash them out properly first.