Echinocereus yavapaiensis is a newer species from central Arizona. This seed was collected near Yarnell, AZ. I checked a few plants and they are hexaploid plants as they are supposed to be. This plant can be very large if planted in the right conditions with good drainage. These plants have taken -17F in our garden and seem unphased by it. Once the plant reaches dish plate size, they really slow down in growth.
I do not guarantee these in a zone 5/6/7 because everyones growing conditions are different but this would be a good trial plant to grow in your cold outdoor garden. Try to plant outdoor 90 days before 1st hard freeze.