Summer plants: plant out after last frost in April or May.  
 
Celosia plants are sold in jumbo 6-packs, ready to plant out.  Celosia does poorly if left overly long in the container.
 
Space plants about 6-12" apart, or wider to leave room for late summer abundant growth.
 
Variety information:
Chief mix: refined variety producing many stems with brain-shaped blooms.  6-pack will contain a mix of colors, mostly red to orange shades.
Tall menagerie: heirloom variety with an unpredictable but delightful range of shapes and colors, including cockscomb, brain, crest, spike, and feathery shapes.