Summer plants: plant out after last frost in April or May.  
 
Branching sunflower plants are sold individually in 2.5-3" pots.  They should be planted out soon after pickup.  
 
Space plants about 12-18" apart.  Healthy plants will grow tall and branch abundantly.
 
Variety info:
Desert Sun: 3-4" multicolor blooms with gold, lemon, and red shades in a variety of looks on a single plant
Lemon Queen: 2-4" blooms in pale yellow with dark centers.  Very classic looking sunflower.