I have abit of a puzzle that at first may seem straightforward but I believe there is a complication.

I have a paired design with each subject being a pot containing 2 plants, 1 treated and 1 untreated. Note that the treatments are applied before planting so they so not run onto the other plant. The problem is that the two plants in the pot compete. My understanding is that a paired t-test makes the assumption that the two plants in the same pot are not independent but I also believe that a paired t-test assumes that the result for one plant does not directly affect the result for the other. Any suggestions as to whether this is a valid layout and if so what analysis can be done?

Thanks