weed killer w/epsom salts

I have a formula for a effective weed killer with vinegar, Epsom salts and dish liquid. On the Epsom salts package it says it promotes rich green foliage. How does it kill weed too???

Epsom salts (MgSO4) will kill any plant if the plant is exposed to toxic levels of Mg or levels of TDS (total dissolved solids) that prevent osmosis or cause reverse osmosis, but this doesn't sound like a reliable herbicide to me unless you're trying to kill plants in containers. More than likely, the mix will kill the above ground portion of the plant, and it will likely regenerate from the roots. The deeper and/or more lignified the root system, the less likely it is that it would be effective.

An aside: Growers should keep in mind that the fact Epsom salts can cause your plants to green up is not a good reason to think more is better. Supplying Mg w/o adding enough Ca to keep the Ca:Mg ratio favorable can cause Ca deficiencies. Adding unneeded Mg also unnecessarily contributes to the EC/TDS levels of the soil solution, which makes it more difficult for the plant to absorb water and the nutrients dissolved therein. An excess of any nutrient has the same potential to limit your plants well-being as a deficiency.

Al

Makes a great foot soak for tired gardening feet. :)

Indeed!

So, Tapla, if I read your post correctly, it'd be best to skip Epsom salts for plants all together?

Yes - unless you have very good reason to believe your plants are suffering from an actual Mg deficiency, or there is good reason to suspect your plants suffer from an antagonistic deficiency of Mg due to excessive Ca levels.

When growers, w/o the means to determine exactly what a plant needs insofar as nutrition is concerned, start adding elements or compounds with the hope that a little more of this or that will make a difference, they're usually right, and the difference is usually a limiting effect. There is a very narrow 'ideal' range of elements in the soil solution, and a significant factor that helps determine the ideal range of any one element is how much of each of the other elements are available for uptake, AND the total volume of nutrients dissolved in the soil solution (EC/TDS). Toxic levels (more than needed) of both Mg and Fe (iron) have the potential to make your plants greener, but greener at the expense of toxicity means limitations.

If you look at a Mulder's Chart, You'll see that an excess of Mg from Epsom salts can inhibit uptake of phosphorous, potassium, and (especially) calcium. If the plant isn't deficient in Mg and you add Epsom salts, it also unnecessarily raises the total level of dissolved solids (TDS) and electrical conductivity (EC - used to determine the level of dissolved solids in solution), which makes it more difficult for the plant to take up water, and because the plant takes up nutrients in that water, it also inhibits nutrient uptake.

If you're fertilizing plants in the ground w/o a soil test, you have no idea what the best course of action is - you're working blind. The goal for fertilizing containerized plants can easily be described, and is essentially the same goal we should be aiming for (after a soil test) when plants in the ground are the topic. Ideally, we would work toward ensuring that all the nutrients plants normally secure from the soil are in the soil solution at all times, in the ratio at which the plant actually uses the nutrients, and at a concentration high enough to ensure no deficiencies yet low enough to ensure the plant isn't impeded in its ability to take up water and the nutrients dissolved in water. For containers, this goal is easily achievable using one water soluble synthetic fertilizer. You CAN use organic forms of nutrition, like fish/seaweed emulsions or various types of meal, but that makes it much more difficult to achieve the goal.

Al

What a wealth of information. Thank you :)