This is cherry plum, not from the ornamental tree but the same fruit sold as Delite cherry plum Q. We have a flowering plum (supposedly ornamental) tree in our front yard.  This year it is covered with small walnut sized plums.  Are these edible?  I am envisioning plum jam if they are edible. A. Yes they are! These plums are sour but great flavor so use lots of sugar and follow your favorite plum jelly or jam recipe. By the way, it can also be used to make wine or infused into vodka or grappa with sugar and let it stand for three to four months or longer. I was put to shame by one of our local winemakers who brought me some of his ornamental plum jam and another with his infused vodka. Purple leaf (ornamental) plum             Because the plums are so small wash and put them into a pot and add enough water to cover them. Boil them for 20 minutes or the skins pop. Mash with a potato masher. Continue to cook another 10 minutes. Let cool.             Strain mashed fruit through cheesecloth or jelly bag. Add Sure Jell to filtered juice and extra water and bring back to a rolling boil, stirring all the time. Add butter and all the sugar and boil for one minute. Skim and pour into jelly jars.  Ornamental Plum Jelly 4 c. plum juice 1 c. water 6 1/2 c. sugar 1 box Sure-jell 1 tsp. butter