As I remembered that experience, a thought came to my mind. What if you could grow the seeds yourself? The most expensive part of making mustard is the seeds and mustard powder (which is just ground mustard seeds). The cost would come down to almost nothing if you had free seeds.
So, pulled out my tin of mustard seeds that I'd bought in 2014 for making relish, and I planted a few in some seed starter. In a few days (to my surprise), they sprouted! I tried transplanting the seeds, but the seedlings died outside in the colder weather. Then I tried sowing some directly in the garden, which was more successful.
My mustard plants grew to be 3-4' tall and fell over from their own weight. Because they were covering some of my other plants, I tied them all to a stake. This seemed to work well.
After the seed pods were done growing, they turned a tan-gray color and dried out. I cut off branches full of pods and put them in a paper grocery bag. After folding up the bag, I took it inside and shook it as hard as I could. The shaking was enough to open a lot of the pods and release the seeds to the bottom of the bag. Then I put on some rubber-coated gloves and crushed the remaining pods with my hands.
There were still a lot of stray pods in with the seeds, so I put it all into a colander, again moving the pods around with my hands. The seeds fell through the colander, while the pods and larger pieces of debris stayed on top. There was a bowl underneath to catch the seeds.
Is It Worth It?
I'll admit- harvesting mustard seeds is a little time-consuming. It's not like other herbs where you just cut them, pop them in the oven to dry and pulverize them. Because of this, and because of the fact that Hubs and I don't use very much mustard, I'll probably just buy mustard in the future. A bottle of $0.88 mustard will last us an entire year.
However, I do think it is worth it to grow your own seeds to use as a spice. I'll probably continue to grow mustard every few years, but not every year. My current supply of homemade mustard powder will last at least two years if I use it as a seasoning and not to make mustard.
If someone is dead set on making their own mustard or buying gourmet mustard (at $8 or more per bottle), than it might be worth it to grow their own seeds to make condiments with. Otherwise, they would be better off just spending $1 every year on mustard. If I use my precious homegrown seeds to make mustard, they are worth less than a dollar. If I use them to make mustard powder and mustard seeds, they are worth $8. I probably have 3-4 hours into planting, weeding, staking, picking, sorting, washing, drying, and powdering the seeds. This brings my hourly wage to about $2 if I make spices, and $0.25 per hour if I make condiments with those spices. It seems wrong, but that's just how everything works out.
The other thing about mustard seeds is that they take up a lot of garden space. In my opinion, this space (that you are going to have to weed and mulch and water anyway) is better used to grow something like tomatoes, which can also be used to make condiments but yield a whole lot more condiment per square foot.
Do you like mustard? Have you ever made your own?