Arugula can be a frustrating crop, sometimes making small plants and bolting to seed before you have eaten much. Sometimes the plants that come up from fallen seeds make the best, biggest plants--and these may come up even in the path where you think they will be scawny from lack of nutrients, rather than in your beautifully fertilized and prepared bed.
But last spring I sampled arugula that made uniformly big, thick leaves, as big as the biggest of my plants ever made. I asked where it came from, and the answer was from The Cook's Garden, a mail or internet order seed company (www.cooksgarden.com).
You know how seed catalogs can make everything sound like the best plant ever? I once bought a broccoli of which catalog copy said "the best thing about this variety is its earliness." I think they spoke the truth. It grew small plants with loose heads that had large buds and it wasn't particularly delicious, but it was definitely early!
I reread the Cooks Garden catalog to see if I would have guessed it was such a good strain. It says they think it is "the best we've found for both flavor and heat tolerance. This large leaved selection lets you harvest young for maximum flavor and texture, and still get the high yields that make the most of small growing spaces." Well maybe, but I am so used to glowing descriptions, I would have though, maybe not.
In any case, have just ordered some garden arugula seeds. I should be able to report if they are as good as the ones I ate in the spring withing 30 days of the arrival of the seed.