Sword fronds should be placed only in one location in your world. They were formed by by a dying nature god, investing his last bit of power to aid the fight against evil.
Every 10 years D8 Fronds will be ripe for harvesting. they will each be +D8 magic to hit and damage, determine size randomly for each.
3 long sword
4 broad sword
6 great sword
they will only "live" for two weeks once they are harvested, if they are harvested by an evil being they die instantly. Magical means can lengthen their lifespan by one week at most. If planted within 24 hours of harvesting a new patch of fronds will be formed in 100 years, only +6 or higher fronds will reproduce in this way