Shepherd Farm was started back in the days where pecan cultivars for the north really were few and far in existence. That time period is when my friend Gary Fernald and company were spending weeks at a time working their way thru vegetation along the Mississippi River from up here near New Boston, IL and down to Missouri. Dan Shepherd who currently runs his fathers farm has since switched most of his fathers trees over to new and improved northern nut cultivars. But as a premise, Dan’s father was grafting anything Gary and company could get their hands on that were superior to other and existing pecans in the wild.
‘Mullahy’ is Gary’s best find. Dan’s father grafted a lot of it and it has remained at Shepherd Farm. The hicans Dan’s father had (and it was a large collection) were grafted 40+ years ago. So that hican you saw above is 40+ years old.
From memory of what I saw in his equipment room and in the orchard: ‘Mullahy’, ‘Shepherd’, ‘Kanza’, Oconee, ‘Pawnee’, ‘Colby’, ‘Elliot’, ‘Osage’; I think he has ‘Oconee’ but I’m not positive. And I know I’m not remembering them all.
Your best bet are Kanza & Hark, Bob. Surely Pawnee is excellent and could be added. I bought 11 pounds of Pawnee while I was at Shepherd Farm. I know what you’re saying. It’s a delicious nut.
I’m going to defer to @Fusion_power for selections other than Kanza or Hark. I don’t know much if anything about Pawnee’s pest problems but if memory serves me, it’s a scab magnet.
As mentioned you need a hardier rootstock for your area. The reason could be very likely that the southern rootstocks that came with plantmegreen were the downfall. Nolin River has everything you need. If you’re going to get a Hark, now’s the time to call John at Nolin. He has Kanza too.
@Fusion_power could be dealing with southern red clay that’s like gooey play dough but even worse. Still, if organice are added the entire hole should never be filled with another media. If he has to break up his soil he should add compost or other organics to get his native soil to the point of being able to drain. And, a large bar should be hammered in the middle of the hole a few feet down or as far as a person is able to go, and then filled with gravel for drainage.