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Using Pool Salt to Kill Weeds: Does It Work? Pros, Cons & Alternatives

Weed control in gardens and veggie patches is of the utmost importance, but many of us prefer not to use hazardous, chemical herbicides and want a safe and effective alternative. Maybe you read somewhere that table salt is an effective alternative and wondered, “will pool salt kill weeds too?”

Pool salt is a potent, non-toxic herbicide that has a detrimental effect on weeds. The efficacy of salt as a weed killer links to several factors, including the amount of salt used, weed density, and the area affected. Using pool salt to kill weeds where other plants grow is not advisable.

Just as pool salt can affect weeds, learn how pool water may impact your plants here.

While not the primary choice of weed killer for most gardeners, salt’s effects on weeds are undeniable. However, how much salt does it take to kill weeds? Does salt affect all weeds in the same manner? And how does salt kill weeds?

Why Pool Salt Kills Weeds

Many gardeners prefer not to use harmful chemicals (herbicides) when controlling weeds and opt for “natural” and non-toxic alternatives.

Pool salt and table salt are (chemically) the same substance; however, pool salt is usually coarser. While salt plays a wondrous role in flavoring food and is essential in trace amounts for plant growth, it has a deadly effect on plants when introduced in a sufficient volume.

Salt causes desiccation in plants (physiological drought). I.e., salt draws water out of a plant, causing plants to dehydrate and eventually die. This process is commonly called a salt (chemical/caustic) burn.

These burns frequently occur on leaves, stems, and buds, where the membranes are soft, while the bark and other older (lignified) material resist desiccation.

Signs of salt damage include:

  • Leaf browning/wilting and dropping out of season
  • Bud scales falling off/buds dying
  • An absence or delay in flower and fruit production
  • Branches shriveling
  • Stunted leaf and stem growth

Salt on a plant’s leaves (particularly when it mixes with water) may prevent or reduce photosynthesis, resulting in plant (weed) deterioration.

Weeds Beside A Pool

Pool Salt Creates Unfavorable Growing Conditions

If there is insufficient salt to kill a weed through a chemical burn, the excess salt in the soil proves fatal, given enough time.

Pool salt thrown on the ground leeches salt minerals and ions into the soil (through rainwater, sunlight, and other processes). These leached minerals accumulate over time.

High levels of salt in the soil prevent plants from absorbing other nutrients and water in the following ways:

  • Preventing the uptake of water. Plant roots in normal conditions have higher salt concentrations than the soil, which leads to water absorption through osmosis. However, when the soil is too salty, plants can’t effectively absorb water.
  • High salt levels in the soil prevent plants from absorbing nitrogen. Nitrogen is essential for plant growth; without it, plants quickly lose condition and die. Plants absorb nitrogen dissolved in groundwater, so they become nitrogen starved if they don’t absorb water.
  • Pool salt consists of sodium chloride molecules (NaCl). Chloride is toxic to plants in higher concentrations. Chloride prevents plants from absorbing nitrogen (particularly in saline soils).
  • Aside from nitrogen, sodium and chloride ions (from broken-down salt) displace other essential macro and micronutrients (e.g., potassium, phosphorus, calcium, magnesium, etc.), resulting in plant deterioration and death.
  • When plants absorb excess salt, their leaves and stems wither and die. Dead leaves, no water, and a lack of nutrients prevent photosynthesis.
  • Plant root morphology changes under higher salt conditions. Plants recognize when there is too much salt in the soil and try to “steer” their roots away from the source.
You may also want to know if pool chlorine can bleach your clothes.

It is important to note that these changes in the soil may not be immediately evident. It may take years (growing seasons) before the effects “take root.” However, using the correct amount of salt yields quicker results.

How Much Salt Do You Need To Kill Weeds?

The volume of pool salt you use as a herbicide depends on the area you want to treat, the types of weeds, and how big and well-established they are.

Most gardeners make a saltwater mixture and apply that to the weeds.

The best method is to start at a lower concentration and (if there are no changes after a few days) increase the concentration.

If you’re using a saltwater solution, you’ll use roughly one part salt to three parts water (1:3). This concentration is enough to manage smaller weeds. If there are no noticeable changes, increase to a 1:2 (salt to water) concentration.

Ensure you spray the solution on the weed (ideally the foliage and stem) without contaminating the surrounding area (particularly if you have grass/other plants close by).

If you're concerned about how pool water might affect your lawn, you can Discover the Impact of Pool Water on Your Lawn. It's particularly important to be careful if you have grass or other plants close by."

If you’re trying to remove weeds from areas that don’t have other plants (paving, asphalt, etc.), a 3:1 salt-to-water ratio is more effective.

If you decide to use salt crystals, add a small number around the base of the weed. These break down over time and leech into the soil. Small weeds need roughly three to four granules.

You might need a handful of pool salt if there are larger weeds.

It is best to start with less and add more as time progresses to prevent excessive soil damage.

How Long Does It Take For Pool Salt To Kill Weeds?

Plants may take up to 10 days to absorb enough salt from the soil to experience the detrimental effects. However, after two days, you should begin to see some effects of the salt.

Premixed salt in water (made into a solution) works significantly quicker than salt crystals thrown on or sown into the ground.

Weeds in Paving

Does Pool Salt Kill All Weeds?

Pool salt is non-selective and affects all plants.

However, how effectively salt kills weeds depends on the following:

  • Plant sizes. Salt is significantly more effective against smaller weeds. Although larger weeds deteriorate, the salt may not kill them completely (they are more resilient and grow back).

Unfortunately, salt is not always effective against trees, large brambles, and ivy bushes, and the amount of salt required to kill these makes it less cost-effective.

  • Plant species. Some plants are more susceptible to salt, while others have a tolerance.

Tolerant species include:

  • Colorado spruce/ Colorado blue spruce (Picea pungens/Picea pungens’ Glauca’)
  • Elm hybrids (Ulmus hybrids)
  • Evergreen Trees and Shrubs
  • Gopher apple (Geobalanus oblongifolius)
  • Hedge maple (Acer campestre)
  • Horse chestnut (Aesculus hippocastanum)
  • Juniper (Juniper spp.)
  • Larch (Larix spp.)
  • Mugo pine (Pinus mugo)
  • Northern red oak (Quercus rubra)
  • Paper birch (Betula papyrifera)
  • Railroad vine (Ipomoea pes-caprae)
  • Red tassel flower (Emilia sonchifolia)
  • Rugosa rose (Rosa rugosa)
  • Sumac (Rhus spp.)
  • Thornless honeylocust (Gleditsia triacanthos var. Inermis)
  • White oak (Quercus alba)
  • White spruce (Picea glauca)
  • Wiry eragrostis (Eragrostis atrovirens)

Is Pool Salt An Effective Means Of Killing Weeds?

While the detrimental effects of pool salt on weeds are beyond reproach, the efficacy of using pool salt as a herbicide is open for debate.

Many gardeners are dead-set against using salt as a weed killer, as the consequences outweigh the benefits. However, those who swear by using salt to control weeds often use rock or table salt (rock salt is used in swimming pools).

The gardeners who benefit most from salt as a herbicide are small-scale gardeners.

Using pool salt in your garden (where you want plants to grow) is not recommended; however, pool salt is most effective in controlling weeds in paving, along driveways, and in other areas where other plants don’t need to grow.

A better control method (in areas that are not overgrown) is to remove the weeds by hand, preventing their return without adding harmful chemicals to the soil.

If you use a saltwater solution on weeds close to other plants, water (with freshwater) the nearby plants thoroughly to wash away any salt contamination.

Not only can pool salt kill weeds, but it can also melt ice. Learn more about this fascinating aspect here.

The Consequences Of Using Pool Salt To Kill Weeds

Although pool salt is a non-toxic herbicide effective in killing weeds, it has several drawbacks.

Salt Has A Delayed Effect In The Soil

Pool (and other) salt may not work immediately. If you sow salt granules into the soil, it may take weeks to months to see the effects.

However, if you use a saltwater solution, you’ll see quicker results.

Salt’s Effects Persist For Years In The Soil

The most significant drawback of using pool salt to kill weeds is that it changes the chemical composition of the soil for years when sown in large enough amounts to control weeds.

Salt Is A Non-Selective “Herbicide”

Unfortunately, salt will also damage the plants you intend to keep; unlike certain chemical herbicides which target specific plants, salt damages all plants (relatively) equally.

Salt changes the soil pH, which makes it impossible for other desirable plants to grow, especially if you use a lot of salt.

The Effects Of Pool Salt Often Spread

Water often translocates sodium and chloride ions. I.e., when it rains, or you water the garden, the salt ions that were by the weeds may “wash” to other parts of the garden and cause adverse effects.

Conclusion

While salt is an effective weed killer, many gardeners prefer not to use it. Salt dries out plants and prevents them from growing effectively; however, salt damages all plants, not only weeds. If you’re set on it, use salt in areas where other plants don’t grow.