All the conditions required to plant the crops have been met, else wise I would not have brought this up.
Edit: I went ahead and checked other crops that had allowed me to plant successfully, and found that they did not meet the declared requirements for planting. Upon fixing those problems, the original crops with which I was having issues allowed me to plant my crops.
Conclusion: It looks like the planting requirements are being checked, but the locations of those requirements are not being checked correctly.