Last year I could not get in the garden early, so I improvised!  I planted my outside pots with salad greens, violas, and herbs.  It worked out great.  I used all different varieties of lettuce and spinach. I found that the different colors and leaf textures adding to the fun of the pots. (Mesclun seed mixes,pablo lettuce,royal red lettuce,spinach, buttercrunch lettuce, black seeded simpson,and much more)  The only requirement was that is was edible.  I added some fresh herbs, parsley, the shorter fernleaf dill, and some "johnny jump ups" for color.

It made my early spring pots look amazing and we ate great fresh greens earlier then if I had waited until this crazy Kentucky weather allowed me to plant in the garden. By the time the lettuce was starting to bolt, the weather was cooperating and I was able to change the pots out to annuals.

I hope you will give this a try, it was a very tasty success.