Alone, rhubarb isn't much to write home about. It's a tad tart. But pair is with some juicy, sweet strawberries and then you've really got something.
Here's what the National Calendar Day website has to say:
"On June 9 of each year, National Strawberry Rhubarb Pie Day is celebrated. Years ago, when home gardening was more common, strawberry rhubarb pie was a popular summer dessert in many households. The sweet/tart combination makes for a delicious pie that is loved by many."