Is it okay to add epsom salt when you plant tomatoes?

http://homeguides.sfgate.com/epson-salts-tomato-pepper-plants-58011.html

yes, and add a bit when when the plants start to flower.

Epsom salts help all plants by adding needed minerals. You can mix a bottle of water with a tsp. Of salts and spray for fertilizer. Or put a spoon in the dirt before planting.

Place some in the bottom of the hole, cover with a bit of soil, then the plant. You do not want to burn the roots. Check this out!

http://balconygardenweb.com/put-8-things-tomato-planting-hole-best-tomatoes-ever/

I always "dumped a bunch" right in with the root ball, and had beautiful healthy plants. It encourages a strong root system, among other things. It does not cause any damage.

I put epsom salts in the soil when I start seeds. I also put a little in the hole when I plant the seedlings and add a little top dressing that will eventually filter through to the roots when watering. I've used it on various types of plants. The tomatoes love it and I had the biggest, greenest basil ever! It is actually magnesium sulfate, a mineral absorbed by the plants. Use it. You won't be disappointed.

I add epson salt to everything I plant in the garden, along with some egg shells coffee grounds, just dig your hole and mix it in well with the dirt you cover your plants with.

It's commonly used for acid-loving rhodies