Hello idreos,
" I would appreciate suggestions for some hardy annuals that will bloom all spring and summer in Maryland "
As Tiffany has suggested, your term "hardy annuals" requires some further definition. In many contexts, "hardy annuals" refers to frost tolerant or cold weather tolerant plants. Some people use the term "hardy" to refer simply to plants that are capable of surviving unfavorable conditions. If you mean "frost tolerance" then you probably should eliminate zinnias from your list of candidates. Zinnias are "tender annuals" and are not frost or freeze tolerant. They are considered to be "easy to grow" and are relatively rapid performers. They can produce blooms in as quickly as 6 weeks from planting the seed, and they can continue blooming right up until the first killing frost in the Fall. So they are good performers in that regard. But if you are looking for cold tolerance, zinnias will probably disappoint you. I grow and breed zinnias as a fun hobby.
This is a photo of one of my zinnia blooms not surviving an early frost.
I will have to be careful not to set any of my indoor zinnia seedlings out into one of my gardens too soon. We can have a snowstorm in April. Although that is considered to be very unusual. But unusual can happen.
ZM
