I usually wait and buy most of my plants in May because I never know when to start my seeds indoors. This handy little chart lets you know when to start seeds indoors as well as when to plant outdoors.
Plant a seedling in an empty eggshell. When time to plant in the ground just cracked the shell some and plant the plant and eggshell. Eggshell is great for the soil. (Put a small hole in bottom of shell for drainage for watering the seedling).