Can I eat the wild mustard roots out of my yard?

All mustard species should be safe (assuming your yard is not contaminated by chemicals), but just for good measure and fun you should look up the specific species. I find the comparison to horseradish to be highly exaggerated, though. I stick to the greens and flower.

http://preparednessadvice.com/food_storage/eating-wild-mustard/#.T8-EoY5FuVg

Eat the tender leaves and the flowers; grind the seeds to make mustard.

Thanks!

I checked out the root today. It smelled like horseradish but it was very hard an uneatable
.

Trying going for the roots of the first year plants, the ones without long stems. A lot of root vegetables become unpalatable early into the second year.