lottsa good answers here...IMO anything between 1/4 inch to 3/4 inch er so...if tap root gets to long it can grow into the fabric of the paper towel and break when tryna remove it to plant..done that once er twice, long ago.. GL
Paper towels are like that! Try using paper coffee filters, they work well, and the paper is finer and the tap roots don't tare as much
