Our Pawnee pecans have started to split their shucks during this last week of September (photo at right). Shuck split in late September is nothing special for Pawnee, but I took this photo to make a point. Like any fruit crop, pecans do not ripen all at the same time. Only one of the three nuts in this cluster has split open. Most pecan cultivars ripen (or split their shucks) over a 7 to 10 day period.
If you ever spot a pecan on a tree that opens significantly later than other nuts on the tree or doesn't open at all, it indicates one of two things: The nut inside is a blank or the nut is infested with pecan weevil.