No. I tried it on roses and it made no difference so suspect there is enough magnesium in the soil. Now if a soil test showed low magnesium that would be differed. Most soil tests aren't that sophisticated.

Unless your land/plot has been heavily cultivated and leached there's usually enough Mg in the soil.

If you're getting poorly vigorous plants or plants who's leaves don't green properly when you're pretty sure you're doing everything else right you probably have some micronutrient problems with your soil.

Mg is one of the most important nutrients excluding the "big 3 - N/K/P" and photosynthesis and phosphorous movement is crippled without sufficient Mg (amongst other things).

If you're not having these issues you probably don't need it.

If you do need it you're probably better off either getting a soil test and delivering exactly what you need to your soil or amending in a mixture of fertilizer heavy on the comon micronutrients.

If you do a search here you'll find numerous discussions on epsom (note spelling) salts use in the garden. I have linked several of them below.

Many swear by its use regardless of soil test results and even those who don't use it will likely admit that it is one of those things that "can't hurt, might help". ;)

When planting tomatoes I add a handful to each prepared hole along with other supplements, mix it in well with the soil to avoid root contact, and water well. Many also use it as a supplemental foliar feeding throughout the growing season. Bottom line - it's your choice. ;)

Dave

Here is a link that might be useful: Epsom Salts discussions