Springtime in the Santa Clara Valley was famously spectacular decades ago, when vast orchards occupied what is now only urban sprawl. Tourists came to see it like some still go to see foliar color of autumn in New England. Most of the orchards were for stone fruits. Only a few in cooler spots were for apples and pears. Only orchards of English walnuts did not bloom colorfully.
Cherry and almond trees typically bloomed first. Prune trees bloomed immediately afterward. Apricot trees were only a few days later. Of course, the schedule of bloom was variable. Prune trees often bloomed just after apricot trees. Various cultivars of cherry started to bloom at slightly different times, even though those that needed to pollinate each other managed to do so.
After the main bloom of all the stone fruits, and after the tourists were gone, the few apple and pear orchards in cooler spots and surrounding hillsides continued the process. Mulberry trees that grew sporadically on roadsides around the orchards bloomed no more colorfully than English walnuts, but somehow produced enough fruit to distract birds from developing stone fruits.
Feral plum trees are a group that was not easy to categorize even before the demise of the orchards. They were not intentionally grown in orchards, or even in home gardens. They just sort of grew wild along creeks or from the roots of grafted stone fruit trees that had been cut down. They were originally grown as understock cultivars, but had naturalized to become truly feral.
Because their fruit was not used for much, they did not get much consideration. We tend to forget that some types bloomed before any of the other stone fruits. To those who do not expect fruit, feral plum trees are as spectacular as productive stone fruit trees.