In Kate Greenaway's Language of Flowers, the entry for Angelica reads: Inspiration.
A creative association with limits
Angelica's assigned message can suit a note to someone whose ideas or encouragement have mattered to you. The strongest version names the contribution: a useful suggestion, an example of persistence or an invitation to try something new.
This is a literary association in a named dictionary. It is not evidence that the plant creates inspiration, improves concentration or has a particular effect on wellbeing. Keep the meaning distinct from any claims about using or consuming the plant.
FAQ
Is inspiration a botanical property of angelica?
No. It is the sentiment attached to the name in this flower-language source.
Source
Kate Greenaway: Language of Flowers, plant-to-meaning entries