Ah, the wonderful mulberry tree (and bush.) They grow just about anywhere and are relatively immune to ordinary pests. Their purple fruit is a favorite of birds and because of the avian laxative effect, a favorite of car washes. The only reason we don't buy pollen yellow cars is the color contrast with purple mulberry guano. Bob Wilson
Bob, There is also a white mulberry. IIRC, not nearly as sweet as the red/black ones. Very similar laxative effect... at least for young boys foraging about. On the plus side, they don't stain your fingers, lips, tongue, shirt front, bright red.
Dad has several of both white and purple mulberries. They're ripe to the max and the birds and other 4 legged critters can't carry them off fast enough. i went down and mowed his place yesterday and the tires of the riding mower are now purple. Fortunately they all ripen at the same time and it doesn't last very long. You learn very quickly where to walk and where not to walk. The purple ones are not near the house by design and are over 100 years old. They're huge.
Around here, the mulberry that grows everywhere is invasive (there's a native but its supposedly not weedy). There are plenty of native berrying shrubs that are yummy and support a greater extent of biodiversity.
There are a couple HUGE mulberry trees near the local creek ... probably at least 50 years old. The fruit it produces seems to be low in sugar ... kind of like highly hybridized black berries. Back to the local tree ... MAN ... NOTHING will stain your hands like these suckers. Ridiculous !