James, you may get better info asking on a US site. The trees wouldn’t grow here they won’t tolerate lower than 10c in the winter, and need a longer summer than than we have. We rarely get the whole three months of summer with high temperatures.
Gardening on the wild, windy west side of Dartmoor.
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They will have someone who can help with your Pecan growing question.
https://garden.org/forums/