Yes, we sometimes stock an agricultural grade of epson salts in the store but haven't lately because it is so widely available at groceries and pharmacies.
Directions on some products are not so good, so we try to have directions for using the products we offer on the web site. For iron, see this page
http://www.hiddenvalleynaturearts.com/acatalog/minerals.htmThis is what it says for treating pots of hibiscus:
Make a small hole in the soil with your finger, put the iron into the hole, cover with soil, and water lightly to wet the soil.
Use 1/4 teaspoon of iron for a plant in a 4" pot.
Use 1/2 teaspoon of iron for a plant in a 6" pot.
Use 3/4 teaspoon of iron for a plant in an 8" pot.
Use 1 teaspoon of iron for a plant in a 2-gallon pot.
Use 1 Tablespoon of iron for large plants in the ground.
It is hard to use too much. It is possible, and if you do the leaves will turn a weird greenish bronze color and then fall off. When I did that once the new growth that came right back was very nicely green and the problem solved.
Also remember that iron (and other minerals) are absorbed best if the pH is around 6.5 and the alkalinity of the water used is less than 100 ppm. If you have a problem with that try the new HVH Acidifying fertilizer which works well with higher pH and higher alkalinity situations.
Charlie
