I have a similar problem for my science class, but it's worded a little differently. I would say that a possible hypothesis is if (one type of flower) is planted alongside (another type), (one type of flower) will grow the best in the soil.
Explanation:
Since there are more than two things being tested, and the comparative stuff isn't known, you kind of just have to pick one. That's the best I could think of. Hope this helps!!!
