You would plant seeds from both wild types in both high and low elevations.
Work Step by Step
If hypothesis 1 is true, the plants will grow at the same height regardless of elevation. If hypothesis 2 is true, the plants will all grow to be short in the higher elevation and all grow tall in the lower elevations. It would also be possible to see a mix of these, whereas the seedlings from shorter plants grow taller at lower elevations but are still much shorter than the seedlings from the taller plants.