I had to look up this answer myself since this is the first year I have grown sweet corn (Growing Challenge), here is the advice I found online:
- When the tassels turn dark brown
- When the juice from kernels are milky white and soft
- From GardenDesk, corn is ready when the raccoons eat it.
From my personal experience, use tassel color to determine if you should even bother checking if it is ready. Use the kernel color to determine if should actually pick it, since when I previous tried just by tassel color it definitely needed another week of growth.
Does anyone else have any proven techniques to pick that perfect ear of corn?