Nebraska Planting Time?

I live in the bottom right corner of Nebraska and I was wondering when the ideal time to plant would be I'm going to try to go as natural as possible, including planting the seed in the excisting ground... no clones... no transplanting.

I live about 35 minutes away from Omaha.

Thanks for any future help.

Also I am going to try to plant two big ass mothers. I wanted to know so I can get as much height out of the VEG- process and during flowering grow some big ass mother fuckers. and harvest in july maybe??