Those of us who grew up with the old fashioned stone fruit orchards or vineyards might remember some of the traditional methods for protecting the ripening fruit from birds. Mulberry trees were grown on the corners of some orchards to keep birds well fed and less hungry for the ripe orchard fruit. Mulberry cultivars were selected to ripen just prior to the fruit within the particular orchards.
The trees were not there to produce fruit to be harvested like the fruit within the orchards was. Most, but not all of what the birds did not consume fell to the ground and rotted. Only small quantities of the overly abundant fruit was taken by a few neighbors who made jam or syrup with with it. Mulberries were a byproduct of the orchards that some put to good use just because it was available.
Decades ago, it was much easier to get a bit of fruit from neglected or naturalized fruit trees in rural regions and on roadsides without offending anyone. Isolated remnants of the old fruit orchards were common. American plum, which had been used as understock for orchard trees, had naturalized in some regions. For those daring enough to harvest them, so had Himalayan blackberry.
Even now, we can find a bit of fruit where do not expect it to be. A few plants that are grown more for their visual appeal can be surprisingly generous with their fruit production. Pineapple guava, which is now popularly grown as a simple evergreen hedge, used to be grown instead for its small tart guavas. Purple leaf plum, as it matures, may not be quite as fruitless as it is purported to be.
The difficulty with the more unfamiliar types of fruit is finding practical uses for it. The native blue elderberry makes excellent jelly or syrup, like black elderberry, but not many of us even know it is edible once cooked. Australian brush cherry, strawberry tree, English hawthorn and ‘Majestic Beauty’ Indian hawthorn, are never overly productive, but might sometimes make enough fruit for jelly.
Of course, no unfamiliar fruit or nut should be eaten prior to confirmation that it is safe for consumption.