One of my goals is to have as many blooming plants and as much color throughout the year. Here is a plan which is working well for me.
March – April
Virginia bluebells.
They come back every year and disappear back into the soil. Scatter the seed around when they are done blooming.
May – June
Annual Poppies
They will reseed themselves, but I choose to save a lot of the seed and plant them again around April 1st.
July to Frost
Salvia – Lady in Red – annual.
These will also reseed themselves and germinate around July 1st.
Butterfly Gardening 
Thank you, Tom. I like your plan. Living in Winston-Salem, NC I have a slightly different planting plan from you in St. Louis. We have yet to see many monarchs thus far this year even though we have many different flowers blooming that usually attract monarch butterflies.
Best Regards,
Charlie