Zinnias in Pots:

Profusion White Zinnia Seeds
Profusion Coral Pink Zinnia Seeds

Observations:

• I planted 4 pots of zinnias this spring.  I was late to sow indoors (late March/early April) and as of today, I am just now seeing a few flower heads appear (most haven't).
• I have about 8-10 plants in each 5 gallon pot and it looks very sparse
• Didn't start to take off until I started fertilizing (early July)
• Had one pot in a lot of shade - it didn't do well so I moved it into the sun.  Doing much better.
• This 'Profusion' series will only look good en-mass - so collect as much seed as possible and sow everything next year

Conclusions:

• Sow in early March indoors, or direct sow April 15th outdoors.  
• Feed 'em early
• Plenty of direct sun
• Over-crowd them.  20-25 per 5 gallon pot - or more!  Consider even direct sowing into fertile soil.  
• The seed packet I had produced a lot of bad plants that didn't grow.  These should be thinned while young... they simply didn't get any better as they grew.  It was apparent which seedlings were going strong and which weren't.  Get rid of the bad ones early. 
• Collect ALL seed for sowing next year