A lot of people use it. I use it occasionally because I use RO water.

Jane

Epsom salts are magnesium sulfate crystals. For people using rainwater, RO or distilled water Epsom salts might be of benefit. Most tap water has enough calcium and magnesium already dissolved in it. Benefits? What are the benefits of Vitamin C vs. Vitamin E or Vitamin A? They each do different things. Good things usually. So what is the benefit of magnesium vs calcium vs pottasium in plant nutrition? Personally I take a multi-vitamin nearly daily. As complete a formula as I can find. My thinking about plant nutrition is similar: a good all round plant fert (Dyna-Gro, Miracle-Gro, Schultz, etc.) and call it good. Drawbacks? Well it is well known in human nutrition that some vitamins (A, E, D) are fat soluble. If you knock back a 25,000IU cod liver oil capsule every day there will come a point where you will experience joint pain, fatigue and other signs of toxicity. When the water that you water with has too much mineral load it pulls water from root cells in an attempt to balance the osmotic pressure across the cell membrane. That is not a good thing. However, a chronic oversupply of magnesium over time causes no harm since the roots will not absorb more than they need. Similarly you can ingest as much Vitamin C as you like as any excess beyond what is needed just goes... out. More than you wanted to know about human vs plant nutrition.

H

Not more than I wanted to know, howard. Thanks.

Jack Peters, of the Jack's Classic fertilizer line said at a seminar at Parkside Orchids that you can't overdo with magnesium as the plant will take only what it needs and discard the rest, just as Howard says. I give all my plants a teaspoon to a gallon once a month, over and above what my fertilizer has in it. And I give plants that are reluctant to bloom an extra dose. In fact, I use it in my garden for all my plants. My tomato plants each get a handful.

Sorry for this stupid question, but what is RO water . please??

In some areas the tap water has too much salt or iron or minerals in general. Then, to grow orchids, you need a Reverse Osmosis system to clean out the water.

The thing to know is that it does too good a job and some compensations must be made to add back in minerals.

If you are growing orchids and don't know about RO, you likely don't need it.

RO water has most of the impurities/minerals taken out of it and is almost bland. It's sold in grocery stores as "Purified" water along with the spring water.

If you're growing orchids and don't know about RO you may still need it. When I moved from New Orleans to Dallas a few of my plants suffered and a couple died. I put it down to humidity. When i moved to a city just outside Dallas many more tanked and i was clueless. I've watered nearly everything with tap water all along under the bad old saying 'if it is good enough to drink its good enough for the plants.' Very recently I FINALLY checked the sodium level and found it is 4 times the upper limit for safe level for the orchids. It had increased with each move! So now I refill water jugs every week with RO water at the grocery store for the orchids. Wish I'd realized sooner. :(