Can {heritage Druid} tap to add mana as she is played. I thought all creatures had SS.
Since there's no tap symbol, yes you can tap her as part of the cost of the ability
RESOLVED
Hays is absolutely correct here, good job! It all comes down to the (lack of, in this case) tap symbol.
"The term "summoning sickness" is an informal term which describes a creature's inability to attack or to use activated abilities that include the tap symbol when it has come under a player's control since the beginning of that player's most recent turn. See rule 302.6. See also Haste."
A similar situation is with {grand architect}