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Alternative Herbicides, a Middle Way

Gardeners can be divided into two camps, the chemical users and the organic growers.  Many of us have our sympathy with the organic growers and surreptitiously use the odd dose of glyphosate or dicamba without investigating if there are any alternatives.  We just need to look into the past to find out what people did to solve the ever present problem of weeds. We are all familiar with cultivation and chemical control of weeds but we are not always aware that there are a large number of commonly used substances that on their own or combined, make effective controllers of unwanted plants.  These substances are easily purchased from grocery shops and in the amounts used, not toxic to children and other garden animals but are surprisingly effective.

Salt
Salt kills plants by reversing the osmotic flow of water into the roots from the surrounding soil.  The stronger salt solution inside plant roots draws in the weaker salt solution in soil water through the root membrane.  Putting salt on the soil makes the soil water into a stronger solution, drawing water from the roots.  In many countries the evaporation of irrigation water has left salts in the soil, creating an imbalance, causing infertility. A pinch of salt at the base will kill an unwanted plant and will be diluted in the next few rain showers.  Salt should only be used in areas where no plant growth is desired, like drives and paths.
Bleach
Household bleach diluted and used in a spray bottle breaks down the leaves.
Heat
Simply pour boiling water on the leaves effectively ‘cooks’ the plant in the soil, and those nearby.  Steam is used by commercial growers to sterilise soil, killing pathogens, seeds and seedlings. A flame gun, much like a plumber’s blowlamp, is extremely effective at killing parts above ground.
Alcohol
Rubbing alcohol or even methylated spirit works by drawing out water from the leaves and quickly evaporating.   It also destroys chlorophyll, the green substance in leaves that helps plants make food, and can also be used for removing grass stains from clothing.
Vinegar
Vinegar is a wonderful organic herbicide, acting on the leaves as a dessicant. It works best on weed seedlings that have not yet developed a sustaining root system that can restore growth.
Soap 
Soap is a great addition to any of the above, acting as a surfactant, allowing substances to stick to leaves and remain effective for longer.
Newspaper and cardboard
Paper products, laid on weeds deprives them of light, but can look untidy among ornamental plants.  Save this one for the allotment, especially for strawberries.
Try testing the effectiveness of the above methods by varying the dilution rate and by combining methods to see which works best for you.  Remember these substances are non-selective contact herebicides, in that they kill or affect all of the plants they touch.  Use a shield of some sort to protect desired plants.