Is CP soap (soapy water) safe for plants?

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TVivian

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This is a very weird question so bear with me.. I live in Southern California and because we're in a severe drought, my city has started restricting water usage. We're only allowed to water our yards three times a week and only during certain days and hours. Because of this my yard has suffered and it got me wondering if I could use bath water to water my plants. (I know, the thought is bizarre!). I would think that most detergents in shampoo isn't safe for them, but what about water that was just used with soap? Also, what about mop water that was made with coconut soap and borax? Id love to hear some opinions on this .. We waste so much water right down the drain!
 
Normal CP in small amounts should be okay - but maybe just in an emergency. I use a soapy water mix on my plants when the lice get on them, far from ideal, but it works. It's not the best for the plant, but much better than anything that a certain large pesticide firm can come up with.......................
 
Years ago, when we were having a drought I would run all of the bath water with an aquarium hose out my bathroom window and into my garden. I never had an issue because the soap was well diluted in the bath water.....I so miss my claw foot tub....

Mop water with borax I don't know about...I am sure there wouldn't be an issue. Maybe do a test with just a few plants and keep a very close eye on them, or dilute the water by a third.

Good Luck!! I am frugal with my water use in a regular season, but a drought season you have to knuckle down and be very careful. I also would keep a basin in my sink for hand washing and then dilute the water and into the garden.

Also, if you grow vegetables, it is considered unwise to water root crops with grey water (the official name for repurposed household water).
 
2 oz per thousand square feet of concentrated soap is actually extremely good for the grass and gardens (it can be used monthly but once the soil flocculates and opens to water and air, it's not necessary to use more than once or twice a year). The reason why this works is complex and related to the cation exchange capacity of the soil and the ion diversity of the soil solution, which I certainly won't bore you with.

You're going to be using more diluted CP soap than that, and CP is a perfectly good substitute for concentrated surfactants. In addition, the soap is biodegradable at the same speed or faster!

While I'd mind excessive amounts, CP in and of itself is not a problem. If you're under that 2 oz of soap per thousand square feet per month, it'll actually be a major advantage.

I would advise that potted plants see pure water every other watering, however, to avoid buildup in the pot. When watering with plain water, give it a third more than required to make the pot pee--that flushes out built-up salts, of which soap is one.

Occasional flushes of soils are always a good idea, but not in the cards for you until winter from my understanding. If even then. Do the best you can.

As Chefmom noted, borax IS a problem. Natural boron levels in the soil vary by region, but even if you're somewhere where it's naturally very low, it can go into toxicity very easily. Optimal levels are around 700 parts per billion (0.7 PPM). Borax is about 11% boron by weight. It doesn't take much to move a soil into the toxic range.

At 1 PPM, no problem. 2 PPM and sensitive plants will start showing symptoms. 5 PPM and the soil profile is toxic to most plants until it washes out, which can take quite some time. Years.

Please avoid the use of borax in any form in your garden water unless you have a soil test (Logan Labs and UMass can help you out there) showing you need it, plus you've had your soil read by an expert (probably me) over on GardenWeb's lawn forum. Prescriptions for correction are generally in the tablespoon per thousand square feet range using Milorganite as a carrier. Southern California is not likely to be a boron-short area due to the lower rainfall. Check out photos of Boron, California to see what excessive boron does to soil...

Fragrance oils, super fat oils, oil types, sodium lactate, salt, sugar, honey, botanicals in the soap, and so on are never a problem (I can't think of a one that would be concentrated enough to be an issue). I probably wouldn't expose a highly sodic soil to more salt or sodium lactate, but we use so little it's unlikely to cause a problem--that's just a precaution. Overly cautious, really.
 
We did that during a drought with no problems. I wouldn't use bath salts and do that without researching more how much salt is safe. But soap? Yeah, it's fine. Gardeners actually treat many pests with a spray that contains soap.
 
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Product Features:

  • Targets and kills aphids, earwigs, grasshoppers, harlequin bugs, leafhoppers, mealy bugs, mites, plant bugs, psyllids, sawfly larvae, soft scales, spider mites, squash bugs, blossom thrips and whiteflies
  • Does not kill beneficial insects when used as directed
  • Can be used up until the day of harvest
  • OMRI Listed® and compliant for use in organic gardening
  • No residual impact on the environment
What's in the Box:

  • 1 Bottle
Specifications:

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  • Contains potassium salts of fatty acids (2%) and seaweed extract
 
We did that during a drought with no problems. I wouldn't use bath salts and do that without researching more how much salt is safe. But soap? Yeah, it's fine. Gardeners actually treat many pests with a spray that contains soap.

That, too. Soft-bodied insects, most notably spider mites and aphids, are intolerant of soapy solutions. Harder bodied insects generally have no issue with them, so the spray is not harmful to bees, butterflies, moths, or beetles (most of which are on the helpful list).

Adding equal weight of any liquid oil to the soap can increase the effects. Neem oil will interfere with the reproductive process, reducing damaging insect populations over time. Only 1/2 oz per thousand square feet of neem is required. More won't hurt your plants but it can be temporarily a little stinky. Neem also makes plant leaves shine and is in most natural leaf shine products.

Rabbits aren't fans of neem oil, Tabasco sauce, and Elmer's glue highly diluted and sprayed on plants. They'll go elsewhere to feed, but it won't impact their nesting areas unless you spray them directly (I never do).

Castor oil and soap can be used (at 1 oz per thousand square feet) to tell voles and moles to move along. Adding a dash of neem oil to that just speeds up the process.
 
This is a very weird question so bear with me.. I live in Southern California and because we're in a severe drought, my city has started restricting water usage. We're only allowed to water our yards three times a week and only during certain days and hours. Because of this my yard has suffered and it got me wondering if I could use bath water to water my plants. (I know, the thought is bizarre!). I would think that most detergents in shampoo isn't safe for them, but what about water that was just used with soap? Also, what about mop water that was made with coconut soap and borax? Id love to hear some opinions on this .. We waste so much water right down the drain!


My moms clothes washer at the old farmhouse has run right outside into the hedgerow since day one. decades of soapy water all year around. All the plants there thrive.
 
Ok, awesome information everyone! I'm glad to know this wasn't such a weird question after all. So.. Yes on Bath water, no on mop water. And I'm only using recycled water on my lawn and patio plants.. Not on anything edible.

I make my laundry soap using shredded, 100% coconut oil soap, borax and washing soda. That's also what I use for mopping and household cleaning (dissolved in water of course) so now I'm curious about the plants thriving where the washer drains.
 
Ok, awesome information everyone! I'm glad to know this wasn't such a weird question after all. So.. Yes on Bath water, no on mop water. And I'm only using recycled water on my lawn and patio plants.. Not on anything edible.

I make my laundry soap using shredded, 100% coconut oil soap, borax and washing soda. That's also what I use for mopping and household cleaning (dissolved in water of course) so now I'm curious about the plants thriving where the washer drains.

If you receive enough rainwater to dispel the boron, no problem. If the plants are tolerant of boron, no problem (most arid and semi-arid plants are extraordinarily tolerant. Bamboo and all grasses [a relative of bamboo] are tolerant.)

Or if you're so boron short and have such a low binding capacity in the soil that the boron can't stick (sand, in other words), no problem--it's actually a net help!
 
Another thought--remember that most washers have a rinse cycle, so you're diluting the soap and borax immediately. That helps, too, and it's essentially pure water.

Your fabric softener is probably not doing any damage. However, if it concerns you, white vinegar makes a wonderful fabric softener and it's completely biodegradable and harmless at that dilution to the plants.
 
I have a friend in Lancaster that runs all her gray (bath, sink, dishwasher, clothes washer) water onto a lawn sprinkler. She hasn't had a problem.
 
Re the worry about bath salts: if you are using 100% Epsom salts, well I know that's good for tomatoes. Regular salt though isn't very good though, I wouldn't think.
 
Thanks again! You're all so helpful!

I don't use bath salts very often and only use shampoo once in awhile.. And never on my kids. They have very coarse hair that loves being washed with handmade soap (plain soap not even shampoo bars!) they take a lot of baths which is where this idea came from. I don't use commercial fabric softener either so It looks like I'm a good candidate for recycling my water.

Now to figure out how to get it all outside haha.
 
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