Alcea rosea.
 
Sow hollyhocks seeds in full sun. Tall spires grow to 4-6' or more, with single, double flowers that fill in empty garden spaces with blooms of gorgeous, deep maroon blooms that look almost black.
 
Flowers grow progressively smaller towards the top of the spire. Great against a fence or a wall, and for hiding unsightly views.
 
Hollyhocks are both tall and drought tolerant, so they are a nice choice for xeriscaping.
 
Biennial
Tall flowers
Rose, pink, white, purple, & lavender
Fills empty areas beautifully
Looks sensational from late spring to frost