I'd like to start growing microgreens indoors. Why do I need to buy specific microgreen seeds? Why can't I use seeds that I'd plant in my garden? It seems like a marketing gimmick to me.
At least that's one person's opinion.
So, I've seen "microgreen mixes" for sale before but here's the deal - they are just a variety of seeds that are commonly used for growing sprouts. I believe this is all a convenience thing, but I'm not a "microgreen expert" and perhaps there's a legitimate reason one would need to buy a special mix.
But I doubt this seriously.
Sprouts are just that - the sprouts of plants that, if given time, would grow into a mature plant, whether that plant is arugula, beet greens, peas, lettuce, tatsoi, endive or a variety of other plants, spinach for instance.
Personally, for the sake of convenience, I'd grab a Mesclun mix. They're tasty (in my opinion) and will all generally sprout at the same time, making it very convenient.
But again, I think there's nothing "special" about the mixes, except that they tend to contain greens that work well.
One other thing - I like the idea of growing mesclun or baby greens because you can generally do the "cut and come again" thing with them. Sprouts, once you snip them off, which I believe is the way this is generally done, will not grow back. Those mesclun mixes and baby greens will generally grow back, at least that's been my experience.
Seeds that are for garden use often require multiple tests and such in order to meet performance standards. They have a much bigger job ahead of them, so a high germination rate, uniform growth, uniform looking plants, uniform maturity, uniform looking harvests, and a number of other things are all necessities. For microgreens, all you need them to do is sprout. This makes the seed-production process a lot simpler, and make it easier to produce a higher number of seeds for lower cost.
Take radishes for example. Good gardening varieties need to be mild, fast, round, and uniformly colored. This means a hybrid is going to bring best results, and can be improved. But the sprouts from hybrid seed, if any, are very variable in comparison to those from heirloom seed. Most microgreen seeds are heirloom for this reason.
Another thing - seeds for garden use are often - but not always - treated with different things, sometimes fungicides, sometimes seed protectant/germination enhancers, so you will need to read the labels of these seeds if you intend to use them as microgreens.