A 'wildseed' in Magical Diary is the term for a student born to a human family that does not have any magical ancestry. Professor Grabiner appears at first to dislike the player's character because she is wildseed, but it turns out later that this is not the case and he is just grumpy to everyone.
Advantages and Disadvantages 
There are advantages to being a wildseed. the fact that you can just decide to quit magic any time. you can simply return home and be with your family, never knowing the existence of magic. If you are NOT wildseed, however, you would have to go somewhere else in the world, all alone, with no family or friends that knew about magic. This is the reason why Virginia envies wildseed students, since she wants to be an athlete. She would have to start over her whole life without her family.
Wildseed students do have the disadvantage of not knowing -at the start- as much about magic and the magical community as that the students in magical families. Another disadvantage is that, under the terms of the Choice, wildseed students are not allowed to discuss or demonstrate magic in front of the uninitiated. That means they have to lie about what they're doing, and make sure to keep their stories straight. This is hard for most wildseed, so many of choose to either abandon their old families entirely, or give up magic and return to their families.
- Unlike the equivalent 'muggleborn' from Harry Potter, there is no widespread discrimination against wildseeds.