Slow Bolt Arugula is simple to grow and quick sprouting as a microgreen. It's a favorite and generally considered a staple of the spicier side of micro greens and baby salad greens. The peppery taste gets less intense as it grows bigger.
Arugula and Cress are both gelatinous seeds which mean they should not undergo the initial soak when sprouting. This will cause them to turn into a huge gelatinous mess which will never sprout, just as you described. Since they are in this mix, we have included a much smaller amount of these two seeds to offset the gel that they form. An initial soak of the entire mix for about 4 hours should do. After this point you can try to sprout them in a mason jar or Easy Sprouter but there are more efficient ways that we recommend.
You’ll need a medium, such as soil, hemp bag, unbleached heavy-duty paper towel, unglazed clay pot bottom, an unbleached coffee filter, or Baby Blanket.
Here are the directions for growing arugula, or any other gelatinous seed such as cress, chia, basil, or flax:
Sprinkle your seeds onto the growing medium. Leave enough space so that most of the seeds aren't touching.
Spritz the seeds with water. They should be damp, but not too wet.
Loosely cover the seed with clear plastic, so they don't dry out. (Plastic wrap or a clear produce bag work for this.)
Spritz the seeds twice a day, or as needed. Try to keep them damp, but not wet.
Once seeds are stuck together and to the growing surface, pour water in to rinse and pour out extra water.
Harvest with scissors when they reach the desired height.
Using the above method, you should be able to grow a 4-12 day sprout or microgreen. If you want to grow longer, you may have to use soil or a fertilizer such as liquid kelp.