Edelweiss and Epsom salt

I was pleased to be able to purchase an Edelweiss plant at Story’s nursery last Friday. I have planted it in a sunny, well drained location and it is nicely budded up! The garden center was packed when I was there despite it being a weekday. I picked up my “Big Beef” tomato transplants, although they will be very overgrown by the time I can safely transplant them into my garden. The soil in my raised beds remains at 50 degrees and that is too cold for good growth. Still, I worry that there will be none left to buy in a few weeks, so I am committed to taking good care of the transplants now, which means daily, if not twice a day, watering and fertilizing.

I did plant my onion transplants and right now I am “curing” the seed potatoes that I cut up. Seed potatoes are whole potatoes that are cut into smaller pieces, with each cut piece having at least one sprout on it. It helps to “cure” these pieces by allowing them to sit out in the sun a few days, which forms callous tissue over the cut sides and helps prevent them from rotting once planted.

As has been the case the past week, no rain was predicted today except for some “spotty” showers. I guess I am in the unfortunate location where these showers appear every single day! This is particularly annoying today since I just sprayed my tomato cages and stakes with full strength household bleach to kill overwintering spores of the early blight disease. I consider this the most important step to combat blight that you can take. Just about everyone who grows tomatoes will have early blight and some seasons it can defoliate the entire plant before the fruit ripens. I will also spray a fungicide at the time of transplanting to delay the onset of disease. By the time the fruit begin to ripen, I don’t want to have to spray anything at all!

I have been reading several “first person testimonials” about how wonderful Epsom salts, aka magnesium sulfate, is for enhancing plant growth, flowering and fruiting. It is true that both magnesium and Sulphur are important micronutrients for good plant growth, but remember they are MICRONUTRIENTS and not MACRONUTRIENTS, as are Nitrogen, Phosphorus and Potassium. Indeed, adding Epsom salts to soils that are deficient in these elements can make a remarkable difference, but the fact is that very, very few local soils are deficient in either of these.

Any garden soil that has had any organic fertilizer or organic mulch applied is unlikely to have such a deficiency. In the 30+ years I worked for Cornell Cooperative Extension, I looked at hundreds of soil test analysis and I don’t recall ever seeing either nutrient listed as “deficient.” Where they can be deficient is in potting soils, or other artificial soils that are commonly used for growing bedding plants, perennials or other plants that will be transplanted. In those cases it is probably more effective to spray a very dilute solution on the leaves to allow direct absorption into the plant.

Magnesium deficiency is also seen when transplants are put in cold soil, as evidenced by stunted, yellow or purple new growth. This has nothing to do with a soil deficiency, just as blossom end rot is not caused by a lack of calcium in the soil, per say. It just indicates that the root system is not yet developed well enough to allow absorption of these micronutrients, due to cold soil and oversized transplants. The problem cures itself quite nicely when the soil warms up and the roots grow, whether Epsom salts are added or not. I think some of these claims reflect the observation that “I have this issue, I added Epsom salts and it went away, therefore Epsom salts cured my problem”. That is a first person testimonial and not a scientific conclusion. The other source of this claim is when someone does something almost exactly the same each year, but this time, after adding the Epsom salts, the results were much, much better. I can understand this if one is dealing with hanging baskets or other container grown plants in artificial soil mixes, but in gardens growing in outdoor soil it is unlikely.

Scientifically, in order to have a meaningful cause and effect, it is imperative to design an experiment that allows for untreated “controls” as well as test subjects. All other possible causes of the phenomena must be carefully controlled to see if the one change that has been made is perhaps the cause for different results. The good news is that adding Epsom salts to your soil, or watering your plants with it, is pretty harmless and if you think it is beneficial, keep on doing it!

Reach Bob Beyfuss at rlb14@cornell.edu.

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