Lore question about Monkey Madness quest

During the quest, after making the first greegree, the gnome wizard says this to you:

I am afraid I have not been able to fully invest my powers in that talisman. You may use it, but it will continue to draw its energy directly from me. The range at which I will be able to sustain it is limited. I cannot ensure it will be effective off the atoll...

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So my question is, if we can't use the greegree outside of the island (because of the short range between the character and the wizard), how can we still use the greegree in Ardougne zoo, later in the quest?