I cut some nuts open today to check on kernel development. In the photo above, you can see large differences in kernel development between cultivars. The early ripening Osage nut has already laid down a large portion of its kernel. The mid-season ripening Kanza nut has entered the gel stage and you can see a translucent thickening just inside the seed coat. Maramec, a late ripening cultivar, has still not achieved full water stage. An explanation on how pecans fill their kernel can be found here.
While I was cutting nuts, I decided to check on our Mandan trees. Mandan is a recently released USDA pecan cultivar that is reported to ripen early, one week earlier than Pawnee. This is the first year our Mandan trees have borne a sizable crop, so I could afford to sacrifice a nut to check the stage of nut development. I also cut a Pawnee and Lakota for comparison (photo above).
Based on the nuts I cut, there is no way Mandan will mature earlier than Pawnee, or even Lakota. Pawnee nuts are now in the dough stage while Lakota nuts are just starting to lay down kernel (early gel stage). Mandan was still in the water stage with no sign of kernel deposition.
I've been wary of Mandan since its release because of questionable kernel quality. Now, I'm concerned that this new cultivar is not as early ripening as advertized.