Upgrade • Cost: 3
Whenever you deal combat damage with an attacker, put a growth rune on this.
While this has at least five growth runes, your units and heroes get +5/+5
Green • Growth Tech II
Dealing 0 combat damage does not count as "dealing combat damage." — Sirlin, 03/04/16
If you deal combat damage to something's armor, that does count as "dealing combat damage." — Sirlin, 03/04/16
Abilities like sparkshot and overpower deal damage at the same time as a thing's normal combat damage. All this damage is considered a single instance of "dealing damage," so the extra damage doesn't add a second rune. — sharpo, 11/07/16