You have to have a good relationship with the peach guy. This is the same with the other characters. The friend page is the bottom tab of the book thing (I think). If the relationship is green it is ok, but if it is red you need to improve.
You have to be friends with them in order for them to accept the items. But don't talk to them or you're character will say something mean.
To build the relationship with the peach man, give him some gifts, such as food. But be careful as he will only accept certain gifts.
As for the rice plant, water it with the cup thing. and eventually it will be ready to grow. this is the same with other plants aswell.
Hope this helped!
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"Have no fear of perfection, you'll never reach it"
-Salvador Dali