The "folk" observation is that squirrels digging in gardens (and pots) usually happens only when there are isolated nut trees and lots of "landscaping" that prevents them planting their nuts at random. When there are sufficient trees, and open spaces with "diggable" soil, they tend to scatter their plantings pretty randomly, and don't bother plantings.

The "method" here works best if there are fairly dense stands of a single type of nut tree fairly densely covering a wide area.

The obvious solution is to replant many of their nuts in a neighbor's (or several neighbors') yard(s) and wait a few years. An isolated one, or a few, nut trees will attract squirrels to an area for the food, but won't necessarily provide sufficient shelter for them to nest in their "natural" tree nests.

A sufficiently dense stand of trees of a single kind will give them both food and shelter, and they'll seldom invade housing and/or gardens. Squirrels normally will not nest within 15 feet or so of the ground, so you do need a reasonable density of fairly tall trees before they'll quit looking for "alternative housing."

A "neighborhood beautification" project in the 1950s gave us four oak trees in our yard, in a 4 or 5 block long "neighborhood" with about 35 similar ones. We have many squirrels, but no particular problems with them that I've heard of. (This is a rather long-term solution, of course.)

The suggestion of getting a dog is marginally helpful. The squirrels in our neighborhood love to tease dogs, and will drive them to the brink of nervous dementia, but eventually the dog will tire of the game and take a nap while the squirrels scamper around him/her to do whatever they want.

Cats are a much more effective deterent, since they really believe they want to catch one of those little rodents, and will keep trying virtually forever. (Sort of like the dumb dog who persists in chasing parked cars?). We used to worry that one of our cats might actually catch one, which would likely be disastrous for the cat; but both the cats and the squirrels seem to enjoy the game, and a "catch" is so unlikely that it shouldn't be a concern. It keeps the squirrels so busy teasing the cats that they don't have time to do more destructive things in our yard.

A peripheral problem with cats is that they like to look for the easy places to "dump," so they may dig in your flower/herb pots and leave something worse than acorns. Usually a layer of marbles on the top of the soil will dissuade the cats, though - if there's sufficient other soft soil available.

The neighbor with the pecan trees has a problem. Oaks are a grocery store, since acorns are nourishing but rather boring. Pecans are a candy store for squirrels, and simple methods are unlikely to work for him.

John