the truth about potash

Potash (K₂CO₃₎ is a really great word, isn't it? I particularly love the fact that it's one of those words that, unless you've heard someone in the know pronouncing it, you constantly have to worry about saying wrong. (For the record, it's pronounced much like pah-tash).

If you're interested in organic gardening, potash is likely one of those things (like epsom salts) that you're eventually going to get to sprinkle on the soil around your plants... just make sure that you sprinkle it on the soil, as I learned the hard way.

Potash, a potassium compound usually derived chemically, mechanically, or as a byproduct of wood-burning, is a great chemical supplement for soil-- and it's organic. It can be crystalline (in which case it's usually white or off-white and looks and feels like very fine sugar) or powdery (in which case it's almost always grey), depending on the purity of its derivation.

It supplements soil with potassium, which is absorbed heavily by some plants and less so by others-- although a potassium deficiency can often look somewhat like a measure of plant diseases, and should be ruled out systematically.

After going to my local ecology center, I found the potash in the bins with the other organic compounds used for garden care, and I found that there was, in fact, no scoop for it. After looking around and surmising that there would be no easy solution to this, I decided, in a feat of sheer brilliance, to break apart and scoop the stuff with my hands. When I left with my 2.5 oz. of the stuff, the tips of my hands were yellow in some spots, brown in others. Washing them fixed this, of course, but that was my first clue how caustic the stuff could be. The other came later, at home, as I sprinkled some potash on my young tomato plants. Some sprinkled on the leaves, which happens often when one casts salt compounds a little too quickly. When I came out the next day, however, I noticed something very strange indeed: the individual grains of potash had turned yellow and were actually burning the tomato leaves. Spots towards the ends of the leaves were black and withered where moisture and gravity had caused the salts to gather.

As it turns out, when combined with water, K₂CO3 and its chemical cousins become caustic, and they'll eat through what's in their path (the leaves, my hands) until they become so dilute that they're ineffective and, ultimately, it washes away. The kicker, though, is that K₂CO3 will actually pull moisture out of the air until it reaches a caustic state, so unless in a covered container, you're going to have a problem.

The moral of the story? Make sure your potash goes on the soil, not the leaves.