Epsom salt application: 1 tablespoon per gallon in a watering can, or 1 1/4 cups in a 20 gal. hose end sprayer.
Every 10 days to 2 weeks. Apply early in the morning or evening when the sun is not so intense.
Epsom salt is available at WalMart - around $2.35 for a package.
The most overlooked nutrient in a garden - Magnesium Sulfate (Epsom Salt) - Executive Gardener (video) http://buff.ly/1LZlEzb