that's society garlic

Society garlic repels mosquitoes. Not a true garlic but in the onion family.

And here I was, thinking that they were African Iris.......Oh, well.

Purple flowers
 

I found this on Amazon.
Google search and then get names & go to local nursery & ask if they have that flower or seeds and get more info.
Good luck with the homework.
Hope this helps.
There are other purple flowers on Amazon. This is just a sample.

DO NOT plant Society Garlic! Take it from someone who knows. They reek of garlic, but not in a good way. Actually, they smell more like skunk spray than garlic. I used to work in a building that had this planted all around it. The smell was unbearable and stayed with me all day even inside the building. I would always think "oh, a skunk must be around" but then would remember the garlic plants. I think they should ban them for use in neighborhood gardens. Lilly of the Nile is pretty, but generic. You can also plant purple salvia which is hardy and can take the heat.

You can break a leaf and smell it, it will smell like garlic if society garlic.