Answer
There are certain specific rules mentioned in the scriptures regarding the plucking of Tulasi leaves for devotional service. However, within ISKCON, the primary principle that is emphasized is that Tulasi leaves should be plucked only for the purpose of serving Krishna and never for any other purpose.
If we follow this fundamental principle—that Tulasi leaves are plucked exclusively for Krishna's service—then there is no offense and no mistake.
For example, when preparing food to be offered to Krishna, it is customary to place a Tulasi leaf on each preparation before offering it. If you pluck Tulasi leaves for this purpose, namely to offer food to Krishna or for His worship, there is no restriction or objection as such.
Srila Prabhupada emphasized the essential principle of devotional service: Tulasi should be engaged in Krishna's service. Therefore, when Tulasi leaves are respectfully plucked for offering to Krishna, the activity is devotional and appropriate.
The important consideration is the purpose. As long as Tulasi leaves are plucked solely for the service and pleasure of Krishna, there is no fault in doing so.
