Simple! Use events.
<>Message: Plant a seed?
<>Show Choices: Yes, No
: [Yes] Handeler
<>Conditional Branch: [Seed] possesed
<>Move Event:: Plant
Change Graphic to Sprout (or whatever the name is)
<>Else Handler
<>Message: You need a seed!
: [No] Handler
<>
[End]
There ya go!