Two non-palms come to mind. Here, in northern Delaware, and in SE Pennsylvania, where I spent half of my life, there are more cultivated specimens of Baldcypress and Magnolia Grandiflora than you can shake a stick at. They each have a very high visibility factor in our landscapes here. Baldcypress is even used (incorrectly, I think) as municipal street trees. Yet neither tree is known to self-propagate in this region. One never sees Baldcypress or Magnolia "volunteers", for example. Perhaps this is different in New Jersey (same latitude) with their sandier soils, but even given our clay soils in PA & DE, you'd think we'd see some random sprouts/seedlings of these two species. Planted specimens of Magnolia Grandiflora are nearly bulletproof hardy here, and Taxodium is even hardier still. Yet, there is something going on that prevents seed from these two trees from spontaneously germinating as they would in their native ranges. Oddly, the "more southern" (and less hardy) Sabal Minor does produce volunteers here, particularly in spots with loose soil and mulch present.