First Wild Pecans are monoecious(Both sex flowers occur
on same tree). The grafted varieties need two or more tree's for pollination to occur.Because these
tree's are wind pollinated.Some pecan tree's have early pollin (before females are receptive)others have late pollin(after Females are receptive) this applies to grafted varieties.Your neighborhood tree's are usually mid season. If you have a grafted tree but no neighboring
Pecans you may need to get another variety to ensure good cross-pollination. So if planting a Kiowa(Great
for pie making because of higher oil content)you will
need a Desireable to pollinate.Hope I explained that well
enough./
Art

I think the link I'm providing below will explain it pretty well. See the 'Pollination' section near the middle of the page.

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Art,
Grafted varieties are no different than non-grafted varieties in this aspect. All pecans are dichogamous to some degree. Wild trees (non-cultivars/"neighborhood trees") will also vary and aren't any more likely to be mid season pollinaters or mid season pollen recipient than any random grafted variety.

Here is a link that might be useful: See Pollination section of this link.

Oops, somehow my link got messed up. Here's the correct one:

Here is a link that might be useful: See Pollination section of this link.

Thanks for your help. I think I know what caused the confusion: the implication was that the tree would take two years to reproduce, and this was a reference to alternate bearing. It had a few pecans last winter (which is why I was sure of cross-pollination--that, and the long catkins on other neighborhood trees :) but I don't know if that means it was an "off" year or the tree was just too young.