The Grass Doctor

why would my liquid fertilizer mix kill my plants?

i have been gardening since i was a little girl with my mother, over 30 years. i have not changed the weak home-made 'formula' of liquid fertilizer concentrate, dish soap, and epsom salts we have always used in the hose-end sprayer, but this spring, the mix killed all my plants! this has NEVER happened to me before--why would this happen? ok, to add some details since some folks have answered... i haven't moved in over 20 years, it's all the same product from last year and everything grew fabulous last year, the hose-end sprayer seems to be working ok, and i sprayed in the morning when it was still cool and partly cloudy, and it was MiracleGro--there was a pinhole in the unopened bag...it got damp--could it have gone bad?

Public Comments

1. Sorry about your plants! Perhaps it was a sunny day when you sprayed? Often it is recommended to spray anything with dish soap when the sun is not shining to avoid burning the leaves. Or perhaps the formula for the dish soap was changed? Not sure about the epsom salts as a spray. I have heard of putting that into the soil, but it may be that could be some problem on the leaves on a sunny day. That formula would be good just watered into the soil and the dish soap wouldn't be necessary.
2. Oops! I recommend Miracle Grow. It can be used as both a foliar fertilizer and root feeding. It could be the dish soap that had different ingredients.
3. It could be that the hose-end sprayer wasn't diluting the mixture properly and it was applied too strongly. Those hose-end sprayers are notorious for not mixing properly. My stupid ex-husband killed his entire crop of greenhouse tomatoes one year by spraying them with an organic foliar solution that the dummy forgot to dilute. As others have said, when foliar spraying, it should be done in the early morning or late afternoon when the sun isn't beating down on the plants. But you want to do it early enough so the leaves dry before dark, otherwise you'd be inviting fungal diseases. Also, make sure you're using real soap and not a detergent. An organic dish soap such as Dr. Bronner's is recommended.
4. First of all detergent or soaps are not fertilizers. They can be used for control of some soft bodied insects but they have no residual effects (bugs need to be sprayed directly) and supply no nutrients. So if you don't have a problem with insects, you shouldn't be spraying soaps. Soaps have a phytotoxicty to plants (foliage damage) and some are more susceptible than others. Your water could also be the culprit as soaps are affected my minerals and hard water produces a chemical change. Here's a university link to the use of soaps. http://www.ext.colostate.edu/pubs/insect/05547.html As far as your epsom salts, many use them as a foliar spray but the jury is still out on that one. There has been no scientific proof on the addition of magnesium sulfate (epsom salts) to the garden. Magnesium sulfate has a fairly high pH and if you add it to high pH soils, it could damage your acid loving plants. My guess is that you have relocated and are gardening in a different zone than you did before. Your best bet would be to contact your local extension service for tips on growing in your for your local climate and conditions.
5. just to answer about the possibility of fertilizer going bad...what all fertilizers contribute to plant growth are elements, and short of a nuclear reaction, elements are immutable...some can become unavailable to plants due to acidity or alkalinity, or if you were using ammonium as a nitrogen fertilizer, for example, it could lose some potency thru evaporation, but it couldnt "go bad" i wouldnt use soap, nor epson salts unless i knew i had a magnesium deficiency in my soil.. calcium and magnesium must be reasonably balanced, too much of one can affect plant use of the other....