There is a list of seeds that can't be used in the science research station in the coding. Unfortunately I don't have access to that list but it's all the mushrooms & plants that came with Supernatural, and any fairly large harvestable. Pumpkins, wonderpetals (huge! flowers) are among the few. So the seeds to be could be any of these and it won't accept it as you can't use those items at all in the station.
edit: Found coding --
<kIngredientBlacklist value="Pumpkin, Pumpkin Vine, Pomelo, Cherries, VampireFruit, Glow Orbs, Spotlight Mushrooms, Red Toadstools, Mycenas, Mandrake, Red Valerian, Wolfsbane, Ginseng, Wonderpetal, Buzzberry, Pomelo Tree, Cherry Tree, Vampire Plant, Ginseng Plant, Wonderpetal Plant, Buzzberry Plant">
<!--Description: Array of Ingredient names that are blocked from being cloned or experimented on.-->