Perhaps, of some interest: If you play a Sim, in another neighborhood, then it is likely that you will have harvestable wild plants, when visiting with another Sim, that's not in that neighborhood.
In other words, if you drop in on the Landgraabs, or Johnny Zest for a while, this should be enough that the wild lemon trees in Oasis Springs are harvestable.
If you visit the Pancakes, then apples should be harvestable in Willow Creek.